AU2002246959A1 - Spliceosome mediated RNA trans-splicing - Google Patents

Description

INHIBITOR OF APOPTOSIS PROTEINS AND NUCLEIC ACIDS AND METHODS FOR MAKING AND USING THEM

PRIORITY INFORMATION

This application claims priority to United States Provisional Application Serial No. 60/260,478, filed January 8, 2001.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH

This invention was made in part with Government support under National

Institutes of Health grants ES02701, AG15402, ES 04699, CA30199 (NCI); U.S. Department of Agriculture grants 97-35302-4406, 9802852; Binational Agriculture

Research and Development grant 96-34339-3532; and, National Institute of

Environmental Health Science grant ES 05707. The Government may have certain rights in the invention.

TECHNICAL FIELD This invention generally pertains to the fields of cell biology and molecular biology. In particular, this invention provides polypeptides comprising the inhibitor of apoptosis protein (IAP) family member BmlAP, initially derived from silkworm Bombyx mori BmN cells, and nucleic acids encoding them, and methods for making and using these compositions, including their use for inhibiting caspase proteases and apoptosis. BACKGROUND

Apoptosis or programmed cell death is a cellular suicide process in which damaged or harmful cells are eliminated from multicellular organisms. Cells undergoing apoptosis have distinct morphological changes including cell shrinkage, membrane blebbing, chromatin condensation, apoptotic body formation and fragmentation. This cell suicide program is evolutionarily conserved across animal and plant species. Apoptosis plays an important role in the development and homeostasis of metazoans and is also critical in insect embryonic development and metamorphosis. Furthermore, apoptosis acts as a host defense mechanism. For example, virally infected cells are eliminated by apoptosis to limit the propagation of viruses. Apoptosis mechanisms are involved in plant reactions to biotic and abiotic insults. Dysregulation of apoptosis has been associated with a variety of human diseases including cancer, neurodegenerative disorders and autoimmune diseases. Accordingly, identification of novel mechanisms to manipulate apoptosis provides new means to study and manipulate this process.

- l - METHODS AND COMPOSITIONS FOR USE IN SPLICEOSOME MEDIATED RNA 4NS-SPLICING

SPECIFICATION The present application is a continuation-in-part of a pending application 09/838,858 filed on April 20, 2001 which is a continuation-in-part of pending application serial number 09/756096 filed January 8, 2001 which is a continuation-in-part of pending application serial number 09/158,863 filed September 23, 1998 which is a continuation-in-part of serial number 09/133,717 filed on August 13, 1998 which is a continuation-in-part of serial number 09/087,233 filed on May 28, 1998, which is a continuation-in-part of pending application serial number 08/766,354 filed on December 13, 1996, which claims benefit to provisional application number 60/008,317 filed on December 15, 1995.

The present invention was made with government support under Grant Nos. SBIRR43DK56526-01 and SBIRR44DK56526-02. The government has certain rights in the invention.

1. INTRODUCTION

The present invention provides methods and compositions for generating novel nucleic acid molecules through targeted spliceosomal trans-splicing. The compositions ofthe invention include pre-trans-splicing molecules (PTMs) designed to interact with a natural target precursor messenger RNA molecule (target pre-mRNA) and mediate a trans -splicing reaction resulting in the generation of a novel chimeric RNA molecule (chimeric RNA). The PTMs ofthe invention are genetically engineered so as to result in the production of a novel chimeric RNA which may itself perform a function, such as inhibiting the translation ofthe RNA, or that encodes a protein that complements a defective or inactive protein in a cell, or encodes a toxin which kills specific cells. Generally, the target pre-mRNA is chosen as a target because it is expressed within a specific cell type thus providing a means for targeting expression ofthe novel chimeric RNA to a selected cell type. The invention further relates to PTMs that have been genetically engineered for the identification of exon/intron boundaries of pre-mRNA molecules using an exon tagging method, hi addition, PTMs can be designed to result in the production of chimeric RNA encoding for peptide affinity purification tags which can be used to purify and identify proteins expressed in a specific cell type. The methods ofthe invention encompass contacting the PTMs ofthe invention with a target pre-mRNA under conditions in which a portion ofthe PTM is trαns-spliced to a portion ofthe target pre-mRNA to form a novel chimeric RNA molecule. The methods and compositions ofthe invention can be used in cellular gene regulation, gene repair and suicide gene therapy for treatment of proliferative disorders such as cancer or treatment of genetic, autoimmune or infectious diseases. In addition, the methods and compositions ofthe invention can be used to generate novel nucleic acid molecules in plants through targeted splicesomal trans-splicing. For example, targeted trαns-splicing may be used to regulate gene expression in plants for treatment of plants diseases, engineering of disease resistant plants or expression of desirable genes in plants. The methods and compositions ofthe invention can also be used to map intron-exon boundaries and to identify novel proteins expressed in any given cell.

2. BACKGROUND OF THE INVENTION

DNA sequences in the chromosome are transcribed into pre-mRNAs which contain coding regions (exons) and generally also contain intervening non- coding regions (introns). Introns are removed from pre-mRNAs in a precise process called splicing (Chow et al, 1977, Cell 12:1-8; and Berget, S.M. et al, 1911, Proc. Natl. Acad. Sci. USA 74:3171-3175). Splicing takes place as a coordinated interaction of several small nuclear ribonucleoprotein particles (snRNP's) and many protein factors that assemble to form an enzymatic complex known as the spliceosome (Moore et al., 1993, in The RNA World, R.F. Gestland and J.F. Atkins eds. (Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y.); Kramer, 1996, Annu. Rev. Biochem., 65:367-404; Staley and Guthrie, 1998, Cell 92:315- Pre-mRNA splicing proceeds by a two-step mechanism. In the first step, the 5' splice site is cleaved, resulting in a "free" 5' exon and a lariat intermediate (Moore, MJ. andP.A. Sharp, 1993, Nature 365:364-368). In the second step, the 5' exon is ligated to the 3' exon with release ofthe intron as the lariat product. These steps are catalyzed in a complex of small nuclear ribonucleoproteins and proteins called the spliceosome. The splicing reaction sites are defined by consensus sequences around the 5' and 3' splice sites. The 5' splice site consensus sequence is AG/GURAGU (where A=adenosine, U = uracil, G = guanine, C = cytosine, R = purine and / = the splice site). The 3¹ splice region consists of three separate sequence elements : the branch point or branch site, a polypyrimidine tract and the 3' splice consensus sequence (YAG). These elements loosely define a 3' splice region, which may encompass 100 nucleotides ofthe intron upstream ofthe 3' splice site. The branch point consensus sequence in mammals is YNYURAC (where N = any nucleotide, Y= pyrimidine). The underlined A is the site of branch formation (the BPA = branch point adenosine). The 3' splice consensus sequence is YAG/G.

Between the branch point and the splice site there is usually found a polypyrimidine tract, which is important in mammalian systems for efficient branch point utilization and 3' splice site recognition (Roscigno, R., F. et al, 1993, J. Biol. Chem. 268: 11222- 11229). The first YAG trinucleotide downstream from the branch point and polypyrimidine tract is the most commonly used 3' splice site (Smith, CW. et al. , 1989, Nature 342:243-247).

In most cases, the splicing reaction occurs within the same pre-mRNA molecule, which is termed -splicing. Splicing between two independently transcribed pre-mRNAs is termed trαns-splicing. Erαns-splicing was first discovered in trypanosomes (Sutton & Boothroyd, 1986, Cell 47:527; Murphy et al, 1986, Cell 47:517) and subsequently in nematodes (Krause & Hirsh, 1987, Cell 49:753); flatworms (Rajkovic et al, 1990, Proc. Natl Acad. Sci. USA, 87:8879; Davis et al, 1995, J. Biol. Chem. 270:21813) and in plant mitochondria (Malek et al, 1997, Proc. Nat'l. Acad. Sci. USA 94:553). In the parasite Trypanosoma brucei, all mRNAs acquire a splice leader (SL) RNA at their 5' termini by trαns-splicing. A 5' leader sequence is also trαns-spliced onto some genes in Caenorhabditis elegans. This mechanism is appropriate for adding a single common sequence to many different transcripts.

The mechanism of trαns-splicing, which is nearly identical to that of conventional c/s-splicing, proceeds via two phosphoryl transfer reactions. The first causes the formation of a 2'-5' phosphodiester bond producing a Υ' shaped branched intermediate, equivalent to the lariat intermediate in cz^'s-splicing. The second reaction, exon ligation, proceeds as in conventional cts-splicing. hi addition, sequences at the 3' splice site and some ofthe snRNPs which catalyze the trαns- splicing reaction, closely resemble their counterparts involved in c/s-splicing. Erαws-splicing may also refer to a different process, where an intron of one pre-mRNA interacts with an intron of a second pre-mRNA, enhancing the recombination of splice sites between two conventional pre-mRNAs. This type of trαns-splicing was postulated to account for transcripts encoding a human immunoglobulin variable region sequence linked to the endogenous constant region in a transgenic mouse (Shimizu et al, 1989, Proc. Natl. Acad. Sci. USA 86:8020). In addition, trans-splicing of c-myb pre-RNA has been demonstrated (Vellard, M. et al. Proc. Nat'l. Acad. Sci., 1992 89:2511-2515) and more recently, RNA transcripts from cloned SV40 trαns-spliced to each other were detected in cultured cells and nuclear extracts (Eul et al, 1995, EMBO. J. 14:3226). However, naturally occurring trans- splicing of mammalian pre-mRNAs is thought to be an exceedingly rare event.

In vitro trαns-splicing has been used as a model system to examine the mechanism of splicing by several groups (Konarska & Sharp, 1985, Cell 46:165-171 Solnick, 1985, Cell 42:157; Chiara & Reed, 1995, Nature 375:510; Pasman and Garcia-Blanco, 1996, Nucleic Acids Res. 24:1638). Reasonably efficient trans- splicing (30% of czs-spliced analog) was achieved between RNAs capable of base pairing to each other, splicing of RNAs not tethered by base pairing was further diminished by a factor of 10. Other in vitro trαns-splicing reactions not requiring obvious RNA-RNA interactions among the substrates were observed by Chiara & Reed (1995, Nature 375:510), Bruzik J.P. & Maniatis, T. (1992, Nature 360:692) and Bruzik J.P. and Maniatis, T., (1995, Proc. Nat'l. Acad. Sci. USA 92:7056-7059). These reactions occur at relatively low frequencies and require specialized elements, such as a downstream 5' splice site or exonic splicing enhancers.

In addition to splicing mechanisms involving the binding of multiple proteins to the precursor mRNA which then act to correctly cut and join RNA, a third mechanism involves cutting and j oining of the RNA by the intron itself, by what are termed catalytic RNA molecules or ribozymes. The cleavage activity of ribozymes has been targeted to specific RNAs by engineering a discrete "hybridization" region into the ribozyme. Upon hybridization to the target RNA, the catalytic region ofthe ribozyme cleaves the target. It has been suggested that such ribozyme activity would be useful for the inactivation or cleavage of target RNA in vivo, such as for the treatment of human diseases characterized by production of foreign of aberrant RNA. The use of antisense RNA has also been proposed as an alternative mechanism for targeting and destruction of specific RNAs. In such instances small RNA molecules are designed to hybridize to the target RNA and by binding to the target RNA prevent translation of the target RNA or cause destruction of the RNA through activation of nucleases.

Until recently, the practical application of targeted trαns-splicing to modify specific target genes has been limited to group I ribozyme-based mechanisms. Using the Tetrahymena group I ribozyme, targeted trans-splicing was demonstrated in E. coli. coli (Sullenger B.A. and Cech. T.R., 1994, Nature 341:619-622) , in mouse fibroblasts (Jones, J.T. et al., 1996, Nature Medicine 2:643-648), human fibroblasts (Phylacton, L.A. et al. Nature Genetics 18:378-381) and human erythroid precursors (Lan et al., 1998, Science 280:1593-1596). While many applications of targeted RNA trαns-splicing driven by modified group I ribozymes have been explored, targeted trαns-splicing mediated by native mammalian splicing machinery, z.e., spliceosomes, has not been previously reported.

3. SUMMARY OF THE INVENTION

The present invention relates to compositions and methods for generating novel nucleic acid molecules through spliceosome-mediated targeted trans-splicing. The compositions ofthe invention include pre-trαns-splicing molecules (hereinafter referred to as "PTMs") designed to interact with a natural target pre-mRNA molecule (hereinafter referred to as "pre-mRNA") and mediate a spliceosomal trαns-splicing reaction resulting in the generation of a novel chimeric RNA molecule (hereinafter referred to as "chimeric RNA"). The methods ofthe invention encompass contacting the PTMs ofthe invention with a natural target pre- mRNA under conditions in which a portion ofthe PTM is spliced to the natural pre- mRNA to form a novel chimeric RNA. The PTMs ofthe invention are genetically engineered so that the novel chimeric RNA resulting from the trαns-splicing reaction may itself perform a function such as inhibiting the translation of RNA, or alternatively, the chimeric RNA may encode a protein that complements a defective or inactive protein in the cell, or encodes a toxin which kills the specific cells. Generally, the target pre-mRNA is chosen because it is expressed within a specific cell type thereby providing a means for targeting expression ofthe novel chimeric RNA to a selected cell type. The target cells may include, but are not limited to those infected with viral or other infectious agents, benign or malignant neoplasms, or components ofthe immune system which are involved in autoimmune disease or tissue rejection. The PTMs ofthe invention may also be used to correct genetic mutations found to be associated with genetic diseases. In particular, double-trans- splicing reactions can be used to replace internal exons. The PTMs ofthe invention can also be genetically engineered to tag exon sequences in a mRNA molecule as a method for identifying intron/exon boundaries in target pre-mRNA. The invention further relates to the use of PTM molecules that are genetically engineered to encode a peptide affinity purification tag for use in the purification and identification of proteins expressed in a specific cell type. The methods and compositions ofthe invention can be used in gene regulation, gene repair and targeted cell death. Such methods and compositions can be used for the treatment of various diseases including, but not limited to, genetic, infectious or autoimmune diseases and proliferative disorders such as cancer and to regulate gene expression in plants. 4. BRIEF DESCRIPTION OF THE DRAWINGS

Figure IA. Model of Pre- Erans-splicing RNA. Figure IB. Model PTM constructs and targeted trαns-splicing strategy. Schematic representation ofthe first generation PTMs (PTM+Sp and PTM- Sp). BD, binding domain; NBD, non-binding domain; BP, branch point; PPT, pyrimidine tract; ss, splice site and DT-A, diphtheria toxin subunit A. Unique restriction sites within the PTMS are indicated by single letters: E; EcoRI; X, Xhol; K, Kpnl; P, Pstl; A, Accl; B, BamHI and H; HindlE.

Figure IC. Schematic drawing showing the binding of PTM+Sp via conventional Watson Crick base pairing to the βHCG6 target pre-mRNA and the proposed cis- and trans-splicing mechanism.

Figure 2A. In vitro trαns-splicing efficiency of various PTM constructs into βHCG6 target. A targeted binding domain and active splice sites correlate with PTM trαns-splicing activity. Full length targeted (pcPTM+Sp), non- targeted (PTM-Sp) and the splice mutants [Py(-)AG(-) and BP(-)Py(-)AG(-)] PTM RNAs were added to splicing reactions containing βHCG6 target pre-mRNA. The products were RT-PCR amplified using primers βHCG-F (specific for target βHCG6 exon 1) and DT-5R (complementary to DT-A) and analyzed by electrophoresis in a 1.5% agarose gel. Figure 2B. In vitro trans-splicing efficiency of various PTM constructs. Full length PTM with a spacer between the binding domain and splice site (PTM+Sp), PTM without the spacer region (PTM+) and short PTMs that contain a target binding domain (short PTM+) or a non-target binding region (PTM-) were added to splicing reactions containing βHCG target pre-mRNA. The products were RT-PCR amplified using primers βHCG-F and DT-3. For reactions containing the short PTMs, the reverse PCR primer was DT-4, since the binding site for DT-3 was removed f om the PTM.

Figure 3. Nucleotide sequence demonstrating the in vitro trans-spliced product between a PTM and target pre-mRNA. The 466 bp trαns-spliced RT-PCR product f om Figure 2 (lane 2) was re-amplified using a 5' biotin labeled forward primer (βHCG-F) and a nested unlabeled reverse primer (DT-3R). Single stranded DNA was purified and sequenced directly using toxin specific DT-3R primer. The arrow indicates the splice junction between the last nucleotide of target βHCG6 exon I and the first nucleotide encoding DT-A.

Figure 4A. Schematic diagram ofthe "safety" PTM and variations, demonstrating the PTM intramolecular base-paired stem, intended to mask the BP and PPT from splicing factors. Underlined sequences represent the βHCG6 intron 1 complementary target-binding domain, sequence in italics indicate target mismatches that are homologous to the BP.

Figure 4B. Schematic of a safety PTM in open configuration upon binding to the target.

Figure 4C. In vitro trαns-splicing reactions were carried out by incubating either safety PTM or safety PTM variants with the βHCG6 target. Splicing reactions were amplified by RT-PCR using βHCG-F and DT-3R primers; products were analyzed in a 2.0% agarose gel. Figure 5. Specificity of targeted trαns-splicing is enhanced by the inclusion of a safety into the PTM. βHCG6 pre-mRNA (250 ng) and β-globin pre- mRNA (250 ng) were annealed together with either PTM+SF (safety) or pcPTM+Sp (linear) RNA (500 ng). In vitro trαns-splicing reactions and RT-PCR analysis were performed as described under experimental procedures and the products were separated on a 2.0% agarose gel. Primers used for RT-PCR are as indicated. Figure 6. In the presence of increasing PTM concentration, cis- splicing is inhibited and replaced by trαns-splicing. In vitro splicing reactions were perfoπned in the presence of a constant amount of βHCG6 target pre-mRNA (100 ng) with increasing concentrations of PTM (pcPTM+Sp) RNA (52-300 ng). RT-PCR for czs-spliced and un-spliced products utilized primers βHCG-F (exon 1 specific) and βHCG-R2 (exon 2 specific - Panel A); primers βHCG-F and DT-3R were used to RT- PCR trans-spliced products (Panel B). Reaction products were analyzed on 1.5% and 2.0% agarose gels, respectively. In panel A, lane 9 represents the 60 min time point in the presence of 300 ng of PTM, which is equivalent to lane 10 in panel B. Figure 7A. PTMs are capable of trαns-splicing in cultured human cancer cells. Total RNA was isolated from each of 4 expanded neomycin resistant H1299 lung carcinoma colonies transfected with pcSp+CRM (expressing non-toxic mutant DT-A) RT-PCR was performed using 1 μg of total RNA and 5' biotinylated βHCG-F and non-biotinylated DT-3R primers. Single stranded DNA was purified and sequenced. Figure 7B. Nucleotide sequence (sense strand) ofthe trαns-spliced product between endogenous βHCG6 target and CRM197 mutant toxin is shown. Two arrows indicate the position ofthe splice junction.

Figure 8 A. Schematic diagram of a double splicing pre-therapeutic mRNA. Figure 8B. Selective trans-splicing of a double splicing PTM. By varying the PTM concentration the PTM can be trans-spliced into either the 5' or the 3' splice site ofthe target.

Figure 9. Schematic diagram ofthe use of PTM molecules for exon tagging. Two examples of PTMs are shown. The PTM on the left is capable of non- specifically trans-splicing into a target pre-mRNA 3' splice site. The other PTM on the right is designed to non-specifically trans-splice into a target pre-mRNA 5' splice site. A PTM mediated trans-splicing reaction will result in the production of a chimeric RNA comprising a specific tag to either the 5' or 3' side of an authentic exon. Figure 10A. Schematic diagram of constructs for use in the lacZ knock-out model. The target lacZ pre-mRNA contains the 5' fragment of lacZ followed by βHCG6 intron 1 and the 3' fragment of lacZ (target 1). The PTM molecule for use in the model system was created by digesting pPTM +SP with Pstl and HindlH and replacing the DT-A toxin with βHCG6 exon 2 (pc3.1PTM2).

Figure 10B. Schematic diagram of restoration of β-Gal activity by Spliceosome Mediated RNA Trans-splicing. Schematic diagram of constructs for use in the lacZ knock-in model (ρc.3.1 lacZ T2). The lacZ target pre-mRNA is identical to that target pre-mRNA used for the knock-out experiments except that it contains two stop codons (TAA TAA) in frame four codons after the 3' splice site. The PTM molecule for use in the model system was created by digesting pPTM +SP with Pstl and Hindlll and replacing the DT-A toxin with functional 3' fragment of lacZ. Figure 11 A. Demonstration of cz^'s-and trαns-splicing when utilizing the lacZ knock-out model. The LacZ splice target 1 pre-mRNA and PTM2 were co-transfected into 293T cells. Total RNA was then isolated and analyzed by PCR for c/s-spliced and trans-spliced products using the appropriate specific primers. The amplified PCR products were separated on a 2% agarose gel.

Figure llB-C. Assays for β-galactosidase activity. 293 cells were transfected with lacZ target 2 DNA alone (panel B) or lacZ target 2 DNA and PTM1 (panel C).

Figure 12 A. Nucleotide sequence of trαns-spliced molecule demonstrating accurate trαns-splicing.

Figure 12B. Nucleotide sequences ofthe czs-spliced product and the trans-spliced product. The nucleotide sequences were those sequences expected for each ofthe different splicing reactions.

Figure 13. Gene repair model for repair ofthe cystic fibrosis transmembrane regulator (CFTR) gene.

Figure 14. RT-PCR demonstration of trαns-splicing between an exogenously supplied CFTR mini-gene target and PTM. Plasmids were co- transfected into 293 embryonic kidney cells. The primers pairs used for RT-PCR reactions are listed above each lane. The lower band (471 bp) in each lane represents a trαns-spliced product. The lower band in lane 1 (471bp) was purified from a 2% Seakem agarose gel and the DNA sequence ofthe band was determined.

Figure 15. DNA sequence ofthe trαns-spliced product (lane 1, lower band shown in Figure 14). The DNA sequence indicates the presence ofthe F508 codon (CTT), exon 9 sequence is contiguous with exon 10 sequence, and the His tag sequence.

Figure 16. Schematic representation of repair of an exogenously supplied CFTR target molecule carrying an F508 deletion in exon 10.

Figure 17. Repair of endogenous CFTR transcripts by exon 10 replacement using a double splicing PTM. The use of a double splicing PTM permits repair ofthe Δ508 mutation with a very short PTM molecule. Figure 18. Model lacZ target consisting of lacZ 5' exon - CFTR mini-intron 9 - CFTR exon 10 (delta 508) - CFTR mini-intron 10 followed by the lacZ 3' exon. Binding domains for PTMs are bracketed.

Figure 19. Schematic representation of double-trans-splicing PTMs designed to restore β-gal function.

Figure 20. Schematic representation of a double-trαns-splicing reaction showing the binding of DSPTM7 with DSCFT1.6 target pre-mRNA.

Figure 21. Important structural elements of DSPTM7. The double splicing PTM has both 3' and 5' functional splice sites as well as binding domains. Figure 22. Schematic diagram of mutant double splicing PTMs.

Figure 23. Accuracy of double-trαns-splicing reaction.

Figure 24. Double-trans-splicing between the target pre-mRNA and the DSPTM7 produces full-length protein. Western blot analysis of total cell lysates using polyclonal anti-β-galactosidase antiserum. Figure 25. Precise internal exon substitution between the DSCFT1.6 target pre-mRNA and DSPTM7 RNA by double-trαns-splicing produces functionally active β-gal protein. Total cell extracts were prepared and assayed for β-gal activity using an ONPG assay.

Figure 26. 3' and 5' splice sites are essential for the restoration of β-gal function by double-trans-splicing reaction.

Figure 27. Double-trαns-splicing: titiation of target and PTM. Different concentrations ofthe target and PTM were co-transfected and analyzed for β-gal activity restoration.

Figure 28. Constructs designed to test the specificity of double-trans-splicing reaction.

Figure 29. Specificity of a double-tr ns-splicing reaction.

Figure 30. Trans-splicing repair ofthe cystic fibrosis gene using a PTM that mediates a double-trans-splicing event.

Figure 31. PTM with a long binding domain masking two splice sites and part of exon 10 in a mini-gene target. Figure 32. Sequence of a single PCR product showing target exon 9 correctly spliced to PTM exon 10 (with modified codons) (upper panel), codon 508 in exon 10 ofthe PTM (middle panel) and PTM exon 10 correctly spliced to target exon 11 (lower panel). The sequence of a repaired target was generated by RT-PCR followed by PCR.

Figure 33. Erans-splicing repair ofthe cystic fibrosis gene using a PTM that can perform 5' exon replacement.

Figure 34. Schematic diagram of three different PTM molecules with different binding domains. Figure 35. Schematic diagram of PTM exon 10 with modified codon usage to reduce antisense effects with its own binding domain.

Figure 36. Sequence of cis- and trans-spliced products.

Figure 37. Model system for repair of messenger RNAs by trans- splicing. (A) Schematic illustration of a defective lacZCF9m splice target used in the present s dy (see Materials and Methods for details). BP, branch point; PPT, polypyrimidine tracts; ss, splice sites and pA, polyadenylation signal. (B) A prototype PTM showing the key components ofthe trαns-splicing domain, and the diagrams of various PTMs showing the binding domain length and approximate positions at which they bind to the target pre-mRNA. Unique restriction sites within the trans-splicing domain are N, Nhe I; S, Sac II; K, Kpn I and E, EcoR V. (C) Schematic diagram showing the binding of a PTM through antisense binding and repair of defective lacZ pre-mRNA through targeted RNA trαns-splicing. Expected cis and trαns-spliced products and the primer binding sites for Lac-9F, Lac-3R and Lac-5R are indicated. Figure 38. Efficient repair of lacZ messenger RNA. Target specific primers, Lac-9F (5' exon) and Lac-3R (3' exon) were used to amplify c/s-spliced products (lanes 1-6), while; target and PTM specific primers, Lac-9F (5' exon) and Lac-5R (3' exon) were used to amplify trans-spliced products (lanes 7-15). 25-50 ng of total RNA was used to measure target cz^'s-splicing (lanes 1-6) and 50-200 ng of total RNA was used to measure PTM induced RNA trans-splicing (lanes 7-12).

Lanes 13-15, 25-50 ng of total RNA from cells transfected with lacZCF9 a control for trαns-splicing. (B) Endogenous mRNA repair by trans-splicing. Lanes 1-3, RNA from cells transfected with PTM-CF14; lanes 4-6, PTM-CF22 and lanes 7-9, PTM- CF24. Lane 10, RNA from mock-transfected cells and lane 11 is a control in which reverse-transcription reaction was omitted. Figure 39. Messenger RNA repair leads to synthesis of full-length β-galactosidase. Lane 1, lacZCF9 (positive control, 5 μg); lane 2, lacZCF9m target alone (25 μg); lane 3, PTM-CF24 alone (25 μg) and lane 4, lacZCF9m target + PTM-CF24 (25 μg).

Figure 40. Messenger RNA repair by SMaRT produces functional β-galactosidase. (A) In sim detection of functional β-galactosidase produced by trans-splicing. 293T cells were either transfected (transient assay) with lacZCF9m target alone (panel A) or co-transfected with lacZCF9m target + PTM-CF24 (panel B) expression plasmids as described above. 48 -hr post-transfection, cells were rinsed with PBS and stained in situ for β-gal activity. (B) Repair of a defective lacZ mRNA produces functional β-galactosidase. Target and PTM, extracts from cells transfected with either lacZCF9m target or PTM-CF24 plasmid alone, and the rest were from cells co-transfected with lacZCF9m target and one ofthe PTMs as indicated. (C) Endogenous mRNA repair by trans-splicing produces functional β-galactosidase. Stable cells expressing an endogenous lacZCF9m pre-mRNA target was transfected with "linear" PTMs (PTM-CF14, PTM-CF22 or PTM-CF24) as described above. Following transfection, total cell lysate was prepared and assayed for β-gal activity. The results presented are the average of two independent transfections.

Figure 41. Messenger RNA repair is specific. (A) Experimental strategy to measure non-specific trans-splicing between lacZHCGlm pre-mRNA and "linear" PTMs. (B) Extended binding domains enhance the specificity of trans- splicing. Lanes 1-3, PTM-CF14; 4-6, PTM-CF22; 7-9, PTM-CF24; 10-12, PTM- CF26 and 13-15, PTM-CF27. (C) PTMs with very long binding domains are capable of increasing specificity. Total cell extract (5 μl) was assayed in solution for β-gal activity and the specific activity was calculated, β-gal activity was normalized to mock and the results presented are the average of two independent transfections. Control, extract from cells transfected with lacZHCGlm target alone and the rest were co-transfected with lacZHCGlm target and one ofthe linear PTMs.

Figure 42. Complete sequence of CFTR PTM 30 (5' exon replacement PTM) showing the trans-splicing domain (underlined) and the coding sequence for exons 1-10 ofthe CFTR gene. Modified codons in exon 10 are underlined and bold.

Figure 43 A. 153 base-pair PTM 24 Binding Domain.

Figure 43B. Complete sequence of CFTR PTM 24 (3' exon replacement PTM) showing the trαns-splicing domain (underlined) and the coding sequence for exons 10-24 ofthe CFTR cDNA. At the end ofthe coding is a histidine tag and the translation stop codon.

Figure 44 A. Detailed stracture ofthe mouse factor VIII PTM containing normal mouse sequences for exons 16-26. BGH=bovine growth hormone 3' UTR (untranslated sequence); Binding Domain=125bp; base changes to eliminate cryptic sites are circled:F5, F6, F7, F8=primer sites. Figure 44B. Schematic diagram showing the extent ofthe binding domain in the mouse factor VIII gene.

Figure 44C. Changes to the promoter in AAV vectors pDLZ20 and pDLZ20-M2 to eliminate cryptic donor sites in sequence upstream ofthe PTM binding domain. Figure 44D. Factor VIII repair model. Schematic diagram of a PTM binding to the 3' splice site of intron 15 ofthe mouse factor VUI gene.

Figure 45. Schematic diagram of a F8 PTM with the trαns-splicing domain eliminated. This represents a control PTM to test whether repair is a result of trαns-splicing. Figure 46. Data indicating repair of factor VIII in Factor VUI knock out mice. Blood was assayed for factor VIII activity using a coatest assay.

Figure 47A. Detailed structure of a mouse factor VIII PTM containing normal sequences for exons 16-26 and a C-terminal FLAG tag. BGH=bovine growth hormone 3"UTR; Binding domain=125 bp. Figure 47B. Detailed stracture of a human or canine factor VIII PTM containing normal sequences for exons 23-26. Figure 48. Transcription Map of HPV- 16.

Figure 49. Disruption of Human Papillomaviras Type 16 Expression by PTM. Schematic diagram of HPV-PTM 2 binding to the 3' splice site ofthe HPV type 16 target pre-mRNA.

Figure 50. E7 Targeting Strategy in which Multiple PTMs are targeted to HPV E7.

Figure 51. PTM Design indicating the binding domain, branch point and polypyrimidine tract.

Figure 52A. HPV-PTM 1 with 80 bp binding domain targeted to 3' ss at 409.

Figure 52B. HPV-PTM 2 with 149 bp binding domain targeted to 3' ss at 409.

Figure 53. Binding Domains of HPV-PTM 3 and 4. Figure 54. Binding Domains of HPV-PTM 5 and 6. Nucleotides in bold are modified to prevent cryptic splicing of PTMs.

Figure 55. Positions of HPV-PTM targeting domains. Figure 56. Erans-splicing Efficiency of HPV-PTMs in 293 T Cells. 293T cells were con-transfected with 2 μg of pi 059 target and 1.5 μg of PTM expression plasmids. 48 hr post-transfection, total RNA was isolated and analyzed by RT-PCR. Target specific primers, oJMD15 and JMD16 were used to amplify czs- spliced products (lanes 1-11, upper panel), while; target and PTM specific primers, oJMD15 and Lac-6R were used to amplify transspliced products (lanes 1-12, lower panel). Lanes 13-14 (upper panel), RNA isolated from cells that are transfected with lacZCF9 and HPV-PTM1 and 2 respectively, hence, serve as controls for evaluating the specificity of HPV-PTMs.

Figure 57. Nucleotide sequence showing the tz-αns-splice junctions between the HPV target pre-mRNA and the PTM. The RT-PCR product was purified and sequenced directly using primer Lac5R (binds to 3' exon ofthe PTM). The arrow indicate trans-splice junction between E6 of HPV pre-mRNA target and lacZ 3' exon ofthe PTM.. Figure 58. Erans-splicing in 293 cells (Co-transfections) Quantification of trans-splicing efficiency was determined using real-time QRT-PCR.

* Figure 59. Erans-splicing efficiency of HPV-PTMs into an endogenous pre-mRNA target. SiHa and CaSki cells were transfected wit 1.5 μg of either HPV-PTMl, 2 or CFTR targets PTM14 or 27 expression plasmids. 48 hr post- transplicing, total RNA was isolated and analyzed by RT-PCR. Trans-splicing between the endogenous HPV target and the PTm was detected using target and PTM specific primers oJMD15 and Lac-16R. The expected trαns-spliced product (418 bp) is clearly visible in cells that are transfected with HPV-PTMs (lanes 2-3 and 5-7) but not in control (lanes 1 and 4). In addition, trαns-splicing is also detected in lane 8 due to non-specific trαns-splicing.

Figure 60. Accurate Erans-splicing of HPV-PTMl in SiHa Cells. Target pre-mRNA was endogenous mRNA. Sequence analysis of trαns-spliced chimeric RNA indicates that trans-splicing is accurate. Figure 61. Quantification of trαns-splicing efficiency in SiHa cells using real-time QRT-PCR.

Figure 62. Erans-splicing efficiency of HPV-PTM 1, HPV-PTM 5, & HPV-PTM 6 in SiHa cells. Analysis of total RNA was performed using RT-PCR. Figure 63. Deletion of polypyrimidine tract abolishes trαns-splicing. Lanes 1 and 2 represent RNA from cells transfected with mutant HPV-PPT. Lanes 3 and 4 represent RNA from cells transfected with HPV-PTM5 plasmid. 269 bp product resulting from trαns-splicing is detected.

Figure 64. Schematic Diagram of a PTM binding to the 5' splice site ofthe HPV mini-gene target and the resulting trans-spliced chimera RNA. Figure 65. Double Erans-splicing. Schematic diagram of a double trans-splicing PTM binding to the 3' and 5' splice sites ofthe HPV mini-gene target. The resultant trαns-spliced mRNA is shown.

Figure 66 A. Trans-splicing by 3' exon replacement. Schematic diagram of a PTM binding to the 3' splice site ofthe HPV mini-gene target. Figure 66B. Trans-splicing by 5' exon replacement. Schematic diagram of a PTM binding to the 5' splice site ofthe HPV mini-gene target. Figure 67. Schematic of a double splicing HPV-PTM designed for internal exon replacement.

5. DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to compositions comprising pre-trans- splicing molecules (PTMs) and the use of such molecules for generating novel nucleic acid molecules. The PTMs of the invention comprise one or more target binding domains that are designed to specifically bind to pre-mRNA, a 3' splice region that includes a branch point, pyrimidine tract and a 3' splice acceptor site and/or a 5' splice donor site; and one or more spacer regions that separate the RNA splice site from the target binding domain. In addition, the PTMs ofthe invention can be engineered to contain any nucleotide sequences such as those encoding a translatable protein product.

The methods ofthe invention encompass contacting the PTMs ofthe invention with a natural pre-mRNA under conditions in which a portion ofthe PTM is trans-spliced to a portion ofthe natural pre-mRNA to form a novel chimeric RNA. The target pre-mRNA is chosen as a target due to its expression within a specific cell type thus providing a mechanism for targeting expression of a novel RNA to a selected cell type. The resulting chimeric RNA may provide a desired function, or may produce a gene product in the specific cell type. The specific cells may include, but are not limited to those infected with viral or other infectious agents, benign or malignant neoplasms, or components ofthe immune system which are involved in autoimmune disease or tissue rejection. Specificity is achieved by modification ofthe binding domain ofthe PTM to bind to the target endogenous pre-mRNA. The gene products encoded by the chimeric RNA can be any gene, including genes having clinical usefulness, for example, therapeutic or marker genes, and genes encoding toxins.

5.1. STRUCTURE OF THE PRE-ER_4NS-SPLICING MOLECULES

The present invention provides compositions for use in generating novel chimeric nucleic acid molecules through targeted trαns-splicing. The PTMs of the invention comprise (i) one or more target binding domains that targets binding of the PTM to a pre-mRNA (ii) a 3' splice region that includes a branch point, pyrimidine tract and a 3' splice acceptor site and/or 5' splice donor site; and (iii) one or more spacer regions to separate the RNA splice site from the target binding domain. Additionally, the PTMs can be engineered to contain any nucleotide sequence encoding a translatable protein product. In yet another embodiment ofthe invention, the PTMs can be engineered to contain nucleotide sequences that inhibit the translation ofthe chimeric RNA molecule. For example, the nucleotide sequences may contain translational stop codons or nucleotide sequences that form secondary structures and thereby inhibit translation. Alternatively, the chimeric RNA may function as an antisense molecule thereby inhibiting translation ofthe RNA to which it binds.

The target binding domain of the PTM may contain multiple binding domains which are complementary to and in anti-sense orientation to the targeted region ofthe selected pre-mRNA. As used herein, a target binding domain is defined as any sequence that confers specificity of binding and anchors the pre-mRNA closely in space so that the spliceosome processing machinery ofthe nucleus can trans-splice a portion ofthe PTM to a portion ofthe pre-mRNA. The target binding domains may comprise up to several thousand nucleotides. In preferred embodiments ofthe invention the binding domains may comprise at least 10 to 30 and up to several hundred nucleotides. As demonstrated herein, the specificity ofthe PTM can be increased significantly by increasing the length ofthe target binding domain. For example, the target binding domain may comprise several hundred nucleotides or more. In addition, although the target binding domain may be "linear" it is understood that the RNA may fold to form secondary structures that may stabilize the complex thereby increasing the efficiency of splicing. A second target binding region maybe placed at the 3' end ofthe molecule and can be incoφorated into the PTM ofthe invention. Absolute complementarity, although preferred, is not required. A sequence "complementary" to a portion of an RNA, as referred to herein, means a sequence having sufficient complementarity to be able to hybridize with the RNA, forming a stable duplex. The ability to hybridize will depend on both the degree of complementarity and the length ofthe nucleic acid (See, for example, Sambrook et al., 1989, Molecular Cloning, A Laboratory Manual, 2d Ed., Cold Spring Harbor Laboratory Press, Cold Spring Harbor, New York). Generally, the longer the hybridizing nucleic acid, the more base mismatches with an RNA it may contain and still form a stable duplex. One skilled in the art can ascertain a tolerable degree of mismatch or length of duplex by use of standard procedures to determine the stability ofthe hybridized complex.

Where the PTMs are designed for use in intron-exon tagging or for peptide affinity tagging, a library of PTMs is genetically engineered to contain random nucleotide sequences in the target binding domain. Alternatively, for intron- exon tagging the PTMs may be genetically engineered so as to lack target binding domains. The goal of generating such a library of PTM molecules is that the library will contain a population of PTM molecules capable of binding to each RNA molecule expressed in the cell. A recombinant expression vector can be genetically engineered to contain a coding region for a PTM including a restriction endonuclease site that can be used for insertion of random DNA fragments into the PTM to form random target binding domains. The random nucleotide sequences to be included in the PTM as target binding domains can be generated using a variety of different methods well known to those of skill in the art, including but not limited to, partial digestion of DNA with restriction enzymes or mechanical shearing of DNA to generate random fragments of DNA. Random binding domain regions may also be generated by degenerate oligonucleotide synthesis. The degenerate oligonucleotides can be engineered to have restriction endonuclease recognition sites on each end to facilitate cloning into a PTM molecule for production of a library of PTM molecules having degenerate binding domains. Binding may also be achieved through other mechanisms, for example, through triple helix formation or protein/nucleic acid interactions such as those in which the PTM is engineered to recognize a specific RNA binding protein, z.e., a protein bound to a specific target pre-mRNA. Alternatively, the PTMs ofthe invention may be designed to recognize secondary structures, such as for example, hairpin structures resulting from intramolecular base pairing between nucleotides within an RNA molecule. The PTM molecule also contains a 3' splice region that includes a branch point, pyrimidine tract and a 3' splice acceptor AG site and/or a 5' splice donor site. Consensus sequences for the 5' splice donor site and the 3' splice region used in RNA splicing are well known in the art (See, Moore, et ah, 1993, The RNA World, Cold Spring Harbor Laboratory Press, p. 303-358). In addition, modified consensus sequences that maintain the ability to function as 5' donor splice sites and 3' splice regions may be used in the practice ofthe invention. Briefly, the 5' splice site consensus sequence is AG/GURAGU (where A=adenosine, U=uracil, G=guanine, C=cytosine, R=purine and /=the splice site). The 3' splice site consists of three separate sequence elements: the branch point or branch site, a polypyrimidine tract and the 3' consensus sequence (YAG). The branch point consensus sequence in mammals is YNYURAC (Y=pyrimidine). The underlined A is the site of branch formation. A polypyrimidine tract is located between the branch point and the splice site acceptor and is important for different branch point utilization and 3' splice site recognition.

Further, PTMs comprising a 3' acceptor site (AG) may be genetically engineered. Such PTMs may further comprise a pyrimidine tract and/or branch point sequence.

Recently, pre-messenger RNA introns beginning with the dinucleotide AU and ending with the dinucleotide AC have been identified and referred to as U12 introns. U12 intron sequences as well as any sequences that function as splice acceptor/donor sequences may also be used in PTMs.

A spacer region to separate the RNA splice site from the target binding domain is also included in the PTM. The spacer region can have features such as stop codons which would block any translation of an unspliced PTM and/or sequences that enhance trαns-splicing to the target pre-mRNA. ♦ i a preferred embodiment ofthe invention, a "safety" is also incorporated into the spacer, binding domain, or elsewhere in the PTM to prevent non-specific trαns-splicing. This is a region ofthe PTM that covers elements ofthe 3' and/or 5' splice site of the PTM by relatively weak complementarity, preventing nonspecific trαns-splicing. The PTM is designed in such a way that upon hybridization ofthe binding /targeting portion(s) ofthe PTM, the 3' and/or 5'splice site is uncovered and becomes fully active.

The "safety" consists of one or more complementary stretches of cis- sequence (or could be a second, separate, strand of nucleic acid) which weakly binds to one or both sides ofthe PTM branch point, pyrimidine tract, 3' splice site and or 5' splice site (splicing elements), or could bind to parts ofthe splicing elements themselves. This "safety" binding prevents the splicing elements from being active (i.e. block U2 snRNP or other splicing factors from attaching to the PTM splice site recognition elements). The binding ofthe "safety" may be disrupted by the binding of the target binding region ofthe PTM to the target pre-mRNA, thus exposing and activating the PTM splicing elements (making them available to trans-splice into the target pre-mRNA).

A nucleotide sequence encoding a translatable protein capable of producing an effect, such as cell death, or alternatively, one that restores a missing function or acts as a marker, is included in the PTM ofthe invention. For example, the nucleotide sequence can include those sequences encoding gene products missing of altered in known genetic diseases. Alternatively, the nucleotide sequences can encode marker proteins or peptides which may be used to identify or image cells. In yet another embodiment ofthe invention nucleotide sequences encoding affinity tags such as, HIS tags (6 consecutive histidine residues) (Janknecht, et al., 1991, Proc. Natl. Acad. Sci. USA 88:8972-8976), the C-terminus of glutathione-S-transferase (GST) (Smith and Johnson, 1986, Proc. Natl. Acad. Sci. USA 83:8703-8707) (Pharmacia) or FLAG (Asp-Tyr-Lys-Asp-Asp-Asp-Lys) (Eastman Kodak/IBI, Rochester, NY) can be included in PTM molecules for use in affinity purification. The use of PTMs containing such nucleotide sequences results in the production of a chimeric RNA encoding a fusion protein containing peptide sequences normally expressed in a cell linked to the peptide affinity tag. The affinity tag provides a method for the rapid purification and identification of peptide sequences expressed in the cell. In a preferred embodiment the nucleotide sequences may encode toxins or other proteins which provide some function which enhances the susceptibility ofthe cells to subsequent treatments, such as radiation or chemotherapy. In a highly preferred embodiment ofthe invention a PTM molecule is designed to contain nucleotide sequences encoding the Diphtheria toxin subunit A (Greenfield, L., et al., 1983, Proc. Nat'l. Acad. Sci. USA 80: 6853-6857). Diphtheria toxin subunit A contains enzymatic toxin activity and will function if expressed or delivered into human cells resulting in cell death. Furthermore, various other known peptide toxins may be used in the present invention, including but not limited to, ricin, Pseudomonus toxin, Shiga toxin and exotoxin A.

Additional features can be added to the PTM molecule either after, or before, the nucleotide sequence encoding a translatable protein, such as polyadenylation signals or 5' splice sequences to enhance splicing, additional binding regions, "safety" -self complementary regions, additional splice sites, or protective groups to modulate the stability ofthe molecule and prevent degradation.

Additional features that may be incoφorated into the PTMs ofthe invention include stop codons or other elements in the region between the binding domain and the splice site to prevent unspliced pre-mRNA expression. In another embodiment ofthe invention, PTMs can be generated with a second anti-sense binding domain downstream from the nucleotide sequences encoding a translatable protein to promote binding to the 3' target intron or exon and to block the fixed authentic c/s-5' splice site (U5 and/or Ul binding sites). PTMs may also be generated that require a double-trαns-splicing reaction for generation of a chimeric trans-spliced product. Such PTMs could be used to replace an internal exon which could be used for RNA repair. PTMs designed to promote two trans-splicing reactions are engineered as described above, however, they contain both 5' donor sites and 3' splice acceptor sites. In addition, the PTMs may comprise two or more binding domains and splicer regions. The splicer regions maybe place between the multiple binding domains and splice sites or alternatively between the multiple binding domains.

Further elements such as a 3' haiφin structure, circularized RNA, nucleotide base modification, or a synthetic analog can be incoφorated into PTMs to promote or facilitate nuclear localization and spliceosomal incoφoration, and intracellular stability. Additionally, when engineering PTMs for use in plant cells it may not be necessary to include conserved branch point sequences or polypyrimidine tracts as these sequences may not be essential for intron processing in plants. However, a 3' splice acceptor site and/or 5' splice donor site, such as those required for splicing in vertebrates and yeast, will be included. Further, the efficiency of splicing in plants may be increased by also including UA-rich intronic sequences. The skilled artisan will recognize that any sequences that are capable of mediating a trαns-splicing reaction in plants may be used.

The PTMs ofthe invention can be used in methods designed to produce a novel chimeric RNA in a target cell. The methods ofthe present invention comprise delivering to the target cell a PTM which may be in any form used by one skilled in the art, for example, an RNA molecule, or a DNA vector which is transcribed into a RNA molecule, wherein said PTM binds to a pre-mRNA and mediates a trαns-splicing reaction resulting in formation of a chimeric RNA comprising a portion of the PTM molecule spliced to a portion of the pre-mRNA.

5.2. SYNTHESIS OF THE ERANS-SPLICING MOLECULES

The nucleic acid molecules ofthe invention can be RNA or DNA or derivatives or modified versions thereof, single-stranded or double-stranded. By nucleic acid is meant a PTM molecule or a nucleic acid molecule encoding a PTM molecule, whether composed of deoxyribonucleotides or ribonucleosides, and whether composed of phosphodiester linkages or modified linkages. The term nucleic acid also specifically includes nucleic acids composed of bases other than the five biologically occurring bases (adenine, guanine, thymine, cytosine and uracil).

The RNA and DNA molecules ofthe invention can be prepared by any method known in the art for the synthesis of DNA and RNA molecules. For example, the nucleic acids may be chemically synthesized using commercially available reagents and synthesizers by methods that are well known in the art (see, e.e., Gait, 1985, Oligonucleotide Synthesis: A Practical Approach, IRL Press, Oxford, England). Alternatively, RNA molecules can be generated by in vitro and in vivo transcription of DNA sequences encoding the RNA molecule. Such DNA sequences can be incoφorated into a wide variety of vectors which incoφorate suitable RNA polymerase promoters such as the T7 or SP6 polymerase promoters. RNAs may be produced in high yield via in vitro transcription using plasmids such as SPS65 (Promega Coφoration, Madison, WT). In addition, RNA amplification methods such as Q-β amplification can be utilized to produce RNAs.

The nucleic acid molecules can be modified at the base moiety, sugar moiety, or phosphate backbone, for example, to improve stability ofthe molecule, hybridization, transport into the cell, etc. For example, modification of a PTM to reduce the overall charge can enhance the cellular uptake ofthe molecule. In addition modifications can be made to reduce susceptibility to nuclease degradation. The nucleic acid molecules may include other appended groups such as peptides (e.g., for targeting host cell receptors in vivo), or agents facilitating transport across the cell membrane (see, e.g., Letsinger et al., 1989, Proc. Natl. Acad. Sci. U.S.A. 86:6553- 6556; Lemaitre et al, 1987, Proc. Natl. Acad. Sci. 84:648-652; PCT Publication No. W088/09810, published December 15, 1988) or the blood-brain barrier (see, e.g., PCT Publication No. W089/10134, published April 25, 1988), hybridization-triggered cleavage agents. (See, e.g., Krol et al, 1988, BioTechniques 6:958-976) or intercalating agents. (See, e.g., Zon, 1988, Phar . Res. 5:539-549). To this end, the nucleic acid molecules may be conjugated to another molecule, e.g., a peptide, hybridization triggered cross-linking agent, transport agent, hybridization-triggered cleavage agent, etc. Various other well-known modifications to the nucleic acid molecules can be introduced as a means of increasing intracellular stability and half- life. Possible modifications include, but are not limited to, the addition of flanking sequences of ribo- or deoxy- nucleotides to the 5' and/or 3' ends ofthe molecule. In some circumstances where increased stability is desired, nucleic acids having modified intemucleoside linkages such as 2'-0-methylation may be preferred. Nucleic acids containing modified intemucleoside linkages may be synthesized using reagents and methods that are well known in the art (see, Uhlmann et al, 1990, Chem. Rev. 90:543-584; Schneider et al, 1990, Tetrahedron Lett. 31:335 and references sited therein). The nucleic acids may be purified by any suitable means, as are well known in the art. For example, the nucleic acids can be purified by reverse phase chromatography or gel electrophoresis. Of course, the skilled artisan will recognize that the method of purification will depend in part on the size ofthe nucleic acid to be purified.

In instances where a nucleic acid molecule encoding a PTM is utilized, cloning techniques known in the art may be used for cloning ofthe nucleic acid molecule into an expression vector. Methods commonly known in the art of recombinant DNA technology which can be used are described in Ausubel et al. (eds.), 1993, Current Protocols in Molecular Biology, John Wiley & Sons, NY; and Kriegler, 1990, Gene Transfer and Expression, A Laboratory Manual, Stockton Press, NY.

The DNA encoding the PTM of interest may be recombinantly engineered into a variety of host vector systems that also provide for replication ofthe DNA in large scale and contain the necessary elements for directing the transcription ofthe PTM. The use of such a construct to transfect target cells in the patient will result in the transcription of sufficient amounts of PTMs that will form complementary base pairs with the endogenously expressed pre-mRNA targets and thereby facilitate a trans-splicing reaction between the complexed nucleic acid molecules. For example, a vector can be introduced in vivo such that it is taken up by a cell and directs the transcription ofthe PTM molecule. Such a vector can remain episomal or become chromosomally integrated, as long as it can be transcribed to produce the desired RNA. Such vectors can be constructed by recombinant DNA technology methods standard in the art. Vectors encoding the PTM of interest can be plasmid, viral, or others known in the art, used for replication and expression in mammalian cells. Expression ofthe sequence encoding the PTM can be regulated by any promoter known in the art to act in mammalian, preferably human cells. Such promoters can be inducible or constitutive. Such promoters include but are not limited to: the SV40 early promoter region (Benoist, C. and Chambon, P. 1981, Nature 290:304-310), the promoter contained in the 3' long terminal repeat of Rous sarcoma virus (Yamamoto et al, 1980, Cell 22:787-797), the heφes thymidine kinase promoter (Wagner et al, 1981, Proc. Natl. Acad. Sci. U.S.A. 78:14411445), the regulatory sequences ofthe metallothionein gene (Brinster et al, 1982, Nature 296:39-42), the viral CMV promoter, the human chorionic gonadotropin-β promoter (Hollenberg et al, 1994, Mol. Cell. Endocrinology 106:111-119), etc. Any type ofplasmid, cosmid, YAC or viral vector can be used to prepare the recombinant DNA construct which can be introduced directly into the tissue site. Alternatively, viral vectors can be used which selectively infect the desired target cell.

For use of PTMs encoding peptide affinity purification tags, it is desirable to insert nucleotide sequences containing random target binding sites into the PTMs and clone them into a selectable mammalian expression vector system. A number of selection systems can be used, including but not limited to selection for expression ofthe heφes simplex virus thymidine kinase, hypoxanthine-guanine phosphoribosyltransterase and adenine phosphoribosyl transferase protein in tk-, hgprt- or aprt- deficient cells, respectively. Also, anti-metabolic resistance can be used as the basis of selection for dihydrofolate tranferase (dhfr), which confers resistance to methotrexate; xanthine-guanine phosphoribosyl transferase (gpt), which confers resistance to mycophenolic acid; neomycin (neo), which confers resistance to aminoglycoside G-418; and hygromycin B phosphotransferase (hygro) which confers resistance to hygromycin. hi a preferred embodiment ofthe invention, the cell culture is transformed at a low ratio of vector to cell such that there will be only a single vector, or a limited number of vectors, present in any one cell. Vectors for use in the practice ofthe invention include any eukaryotic expression vectors, including but not limited to viral expression vectors such as those derived from the class of retroviruses or adeno-associated viruses.

5.3. USES AND ADMINISTRATION OF TRANS-SPUCNG MOLECULES

5.3.1. USE OF PTM MOLECULES FOR GENE REGULATION, ^• GENE REPAIR AND TARGETED CELL DEATH

The compositions and methods ofthe present invention will have a variety of different applications including gene regulation, gene repair and targeted cell death. For example, trans-splicing can be used to introduce a protein with toxic properties into a cell. In addition, PTMs can be engineered to bind to viral mRNA and destroy the function ofthe viral mRNA, or alternatively, to destroy any cell expressing the viral mRNA. In yet another embodiment ofthe invention, PTMs can be engineered to place a stop codon in a deleterious mRNA transcript thereby decreasing the expression of that transcript.

In an embodiment ofthe invention PTM molecules were designed to bind to papilloma virus RNA and inhibit the function ofthe viral RNA. Specifically anti-HPV PTMs were designed to specifically target HPV pre-mRNAs and result in the expression of a disruptive or toxic protein only in the HPV-infected cancer cells. Thus, the invention provides PTM molecules designed to inhibit the function of papilloma virus RNA. Such papilloma viruses, include but are not limited to mammalian papillomaviruses including human papillomaviruses.

The papilloma viruses are a group of small DNA viruses which induce papiUomas (warts) in a variety of vertebrates, including human. In addition, human papilloma viras is one ofthe most common causes of sexually transmitted diseases in the country and the vast majority of cervical cancers are associated with oncogenic human papillomaviruses and express viral mRNAs encoding the E6 and E7 oncoproteins. Thus, the PTM molecules ofthe invention may be used to inhibit the proliferation of papillomaviruses within an infected host.

Targeted trans-splicing, including double-trans-splicing reactions, 3' exon replacement and/or 5' exon replacement can be used to repair or correct transcripts that are either truncated or contain point mutations. The PTMs ofthe invention are designed to cleave a targeted transcript upstream or downstream of a specific mutation or upstream of a premature 3' and correct the mutant transcript via a trans-splicing reaction which replaces the portion ofthe transcript containing the mutation with a functional sequence.

In addition, double trαns-splicing reactions may be used for the selective expression of a toxin in tumor cells. For example, PTMs can be designed to replace the second exon ofthe human β -chronic gonadotropin-6 (βhCG6) gene transcripts and to deliver an exon encoding the subunit A of diptheria toxin (DT-A). Expression of DT-A in the absence of subunit B should lead to toxicity only in the cells expressing the gene. βhCG6 is a prototypical target for genetic modification by trans-splicing. The sequence and the structure ofthe βhCG6 gene are completely known and the pattern of splicing has been determined. The βhCG6 gene is highly expressed in many types of solid tumors, including many non-germ line tumors, but the βhCG6 gene is silent in the majority cells in a normal adult. Therefore, the βhCG6 pre-mRNA represents a desirable target for a trans-splicing reaction designed to produce tumor-specific toxicity.

The first exon of βhCG6 pre-mRNA is ideal in that it encodes only five amino acids, including the initiator AUG, which should result in minimal interference with the proper folding ofthe DT-A toxin while providing the required signals for effective translation ofthe trans-spliced mRNA. The DT-A exon, which is designed to include a stop codon to prevent chimeric protein formation, will be engineered to trans-splice into the last exon ofthe βhCG6 gene. The last exon ofthe βhCG6 gene provides the construct with the appropriate signals to polyadenylate the mRNA and ensure translation.

Cystic fibrosis (CF) is one ofthe most common fatal genetic disease in humans. Based on both genetic and molecular analyses, the gene associated with cystic fibrosis has been isolated and its protein product deduced (Kerem, B.S. et al., 1989, Science 245:1073-1080; Riordan et al., 1989, Science 245:1066-

1073;Rommans, et al, 1989, Science 245:1059-1065). The protein product ofthe CF associated gene is called the cystic fibrosis transmembrane conductance regulator (CFTR). In a specific embodiment ofthe invention, a trαns-splicing reaction will be used to correct a genetic defect in the DNA sequence encoding the cystic fibrosis transmembrane regulator (CFTR) whereby the DNA sequence encoding the cystic fibrosis trans-membrane regulator protein is expressed and a functional chloride ion channel is produced in the airway epithelial cells of a patient.

Population studies have indicated that the most common cystic fibrosis mutation is a deletion ofthe three nucleotides in exon 10 that encode phenylalanine at position 508 ofthe CFTR amino acid sequence. As indicated in Figure 15, a trαns- splicing reaction was capable of correcting the deletion at position 508 in the CFTR amino acid sequence. The PTM used for correction ofthe genetic defect contained a CFTR BD intron 9 sequence, a spacer sequence, a branch point, a polypyrimidine tract, a 3' splice site and a wild type CFTR BD exon 10 sequence (Figure 13). The successful correction ofthe mutated DNA encoding CFTR utilizing a trαns-splicing reaction supports the general application of PTMs for correction of genetic defects. HemophiliaA is an X-linked bleeding disorder characterized by a deficiency in the activity of factor VUI, a n important component ofthe coagulation cascade. The incidence of hemophilia A is approximately 1 in 5,000 to 10,000 males. Affected individuals suffer joint and muscle hemorrhage, easy bruising, and prolonged bleeding from wounds. Hemophilia A arises from a variety of mutations within the factor VUI gene. The gene comprises 26 exons and spans 186 kb. About 95 percent of those patients with hemophilia A in whom mutations have been characterized, have point mutations in the gene. In a specific embodiment ofthe invention, a trans-splicing reaction will be used to correct a genetic defect in the DNA sequence encoding factor VIE whereby the DNA sequence encoding the factor VIII protein is expressed and a functional clotting factor is produced in the plasma of a patient. The PTMs ofthe invention can be genetically engineered to repair any exon of interest, or combination of exons for the puφose of correcting a defect in the coding region ofthe factor VIII gene. Genetic studies have indicated that the most common factor VIII mutation(s) are be generated. As indicated in Figure 46, a trans-splicing reaction was capable of correcting the mutation in the factor VIE amino acid sequence. The mutation was created by an insertion ofthe neomycin gene into exon 16 and intron 16 ofthe mouse gene, interrupting the open reading frame of exon 16 and eliminating intron 16's 3' splice donor site. The PTM used for correction ofthe genetic defect contained factor VUI exons 16-24 coding sequences, a spacer sequence, a branch point, a polypyrimidine tract, and a 3' acceptor splice (Figure 44 A). The successful correction ofthe mutated DNA encoding factor VUI utilizing a trans-splicing reaction further supports the general application of PTMs for correction of genetic defects. The methods and compositions ofthe invention may also be used to regulate gene expression in plants. For example, trans-splicing may be used to place the expression of any engineered gene under the natural regulation of a chosen target plant gene, thereby regulating the expression ofthe engineered gene. Erans-splicing may also be used to prevent the expression of engineered genes in non-host plants or to convert an endogenous gene product into a more desirable product. In a specific embodiment ofthe invention tran-splicing may be used to regulate the expression ofthe insecticidal gene that produces Bt toxin (Bacillus thuringiensis). For example, the PTM maybe designed to trans-splice into an injury response gene (pre-mRNA) that is expressed only after an insect bites the plant. Thus, all cells ofthe plant would carry the gene for Bt in the PTM, but the cells would only produce Bt when and where an insect injures the plant. The rest ofthe plant will make little or no Bt. A PTM could trans-splice the Bt gene into any chosen gene with a desired pattern of expression. Further, it should be possible to target a PTM so that no Bt is produced in the edible portion ofthe plant.

One advantage associated with the use of PTMs is that the PTM acquires the native gene control elements ofthe target gene, thus, reducing the time and effort that might otherwise be spent attempting to identify and reconstitute appropriate regulatory sequences upstream of an engineered gene. Thus, expression ofthe PTM regulated gene should occur only in those plant cells containing the target pre-mRNA. By targeting a gene not expressed in the edible portion ofthe plant or in the pollen, trans-splicing can alleviate opposition to genetically modified plants, as consumers would not be eating the proteins made from modified genes. The edible portion of such crops should test negative for genetically modified proteins.

In addition, PTM can be targeted to a unique sequence ofthe host gene that is not present in other plants. Therefore, even if the gene (DNA) which encodes the PTM jumps to another species of plant, the PTM gene will not have an appropriate target for trαns-splicing. Thus, trans-splicing offers a "fail-safe" mode for prevention of gene "jumping" to other plant species: the PTM gene will be expressed only in the engineered host plant, which contains the appropriate target pre-mRNA. Expression in non-engineered plants would not be possible. Erans-splicing also provides a more efficient way to convert one gene product into another. For example, trαns-splicing ribozymes and chimeric oligos can be incoφorated into com genomes to modify the ratio of saturated to unsaturated oils.

ErαHs-splicing can also be used to convert one gene product into another.

Various delivery systems are known and can be used to transfer the compositions ofthe invention into cells, e.g. encapsulation in liposomes, microparticles, microcapsules, recombinant cells capable of expressing the composition, receptor-mediated endocytosis (see, e.g., Wu and Wu, 1987, J. Biol.

Chem. 262:4429-4432), construction of a nucleic acid as part of a retroviral or other vector, injection of DNA, electroporation, calcium phosphate mediated transfection, etc. The compositions and methods can be used to treat cancer and other serious viral infections, autoimmune disorders, and other pathological conditions in which the alteration or elimination of a specific cell type would be beneficial.

Additionally, the compositions and methods may also be used to provide a gene encoding a functional biologically active molecule to cells of an individual with an inherited genetic disorder where expression of the missing or mutant gene product produces a normal phenotype.

In a preferred embodiment, nucleic acids comprising a sequence encoding a PTM axe administered to promote PTM function, by way of gene delivery and expression into a host cell. In this embodiment ofthe invention, the nucleic acid mediates an effect by promoting PTM production. Any ofthe methods for gene delivery into a host cell available in the art can be used according to the present invention. For general reviews ofthe methods of gene delivery see Strauss, M. and

Barranger, J.A., 1997, Concepts in Gene Therapy, by Walter de Gruyter & Co.,

Berlin; Goldspiel et al, 1993, Clinical Pharmacy 12:488-505; Wu and Wu, 1991, Biotherapy 3:87-95; Tolstoshev, 1993, Ann. Rev. Pharmacol. Toxicol. 33:573-596;

Mulligan, 1993, Science 260:926-932; and Morgan and Anderson, 1993, Ann. Rev.

Biochem. 62:191-217; 1993, TIBTΕCH 11(5):155-215. Exemplary methods are described below.

Delivery ofthe nucleic acid into a host cell may be either direct, in which case the host is directly exposed to the nucleic acid or nucleic acid-carrying vector, or indirect, in which case, host cells are first transformed with the nucleic acid in vitro, then transplanted into the host. These two approaches are known, respectively, as z^'n vivo or ex vivo gene delivery. hi a specific embodiment, the nucleic acid is directly administered in vivo, where it is expressed to produce the PTM. This can be accomplished by any of numerous methods known in the art, e.g. , by constructing it as part of an appropriate nucleic acid expression vector and administering it so that it becomes intracellular, e.g. by infection using a defective or attenuated retroviral or other viral vector (see U.S. Patent No. 4,980,286), or by direct injection of naked DNA, or by use of microparticle bombardment (e.g., a gene gun; Biolistic, Dupont), or coating with hpids or cell-surface receptors or transfecting agents, encapsulation in liposomes, microparticles, or microcapsules, or by administering it in linkage to a peptide which is known to enter the nucleus, by administering it in linkage to a ligand subject to receptor-mediated endocytosis (see e.g., Wu and Wu, 1987, J. Biol. Chem. 262:4429- 4432). In a specific embodiment, a viral vector that contains the PTM can be used. For example, a retroviral vector can be utilized that has been modified to delete retroviral sequences that are not necessary for packaging ofthe viral genome and integration into host cell DNA (see Miller et al, 1993, Meth. Enzymol. 217:581-599). Alternatively, adenoviral or adeno-associated viral vectors can be used for gene delivery to cells or tissues. (See, Kozarsky and Wilson, 1993, Current Opinion in Genetics and Development 3:499-503 for a review of adenovirus-based gene delivery).

Another approach to gene delivery into a cell involves transferring a gene to cells in tissue culture by such methods as electroporation, lipofection, calcium phosphate mediated transfection, or viral infection. Usually, the method of transfer includes the transfer of a selectable marker to the cells. The cells are then placed under selection to isolate those cells that have taken up and are expressing the transferred gene. The resulting recombinant cells can be delivered to a host by various methods known in the art. In a preferred embodiment, the cell used for gene delivery is autologous to the host cell. The present invention also provides for pharmaceutical compositions comprising an effective amount of a PTM or a nucleic acid encoding a PTM, and a pharmaceutically acceptable carrier. In a specific embodiment, the term "pharmaceutically acceptable" means approved by a regulatory agency ofthe Federal or a state government or listed in the U.S. Pharmacopeia or other generally recognized pharmacopeia for use in animals, and more particularly in humans. The term "carrier" refers to a diluent, adjuvant, excipient, or vehicle with which the therapeutic is administered. Examples of suitable pharmaceutical carriers are described in "Remington's Pharmaceutical sciences" byE.W. Martin. In specific embodiments, pharmaceutical compositions are administered: (1) in diseases or disorders involving an absence or decreased (relative to normal or desired) level of an endogenous protein or function, for example, in hosts where the protein is lacking, genetically defective, biologically inactive or underactive, or under expressed; or (2) in diseases or disorders wherein, in vitro or in vivo, assays indicate the utility of PTMs that inhibit the function of a particular protein . The activity ofthe protein encoded for by the chimeric mRNA resulting from the PTM mediated trans-splicing reaction can be readily detected, e.g., by obtaining a host tissue sample (e.g., from biopsy tissue) and assaying it in vitro for mRNA or protein levels, structure and/or activity ofthe expressed chimeric mRNA. Many methods standard in the art can be thus employed, including but not limited to immunoassays to detect and/or visualize the protein encoded for by the chimeric mRNA (e.g., Western blot, immunoprecipitation followed by sodium dodecyl sulfate polyacrylamide gel electrophoresis, immunocytochemistry, etc.) and/or hybridization assays to detect formation of chimeric mRNA expression by detecting and/or visualizing the presence of chimeric mRNA (e.g. , Northern assays, dot blots, in situ hybridization, and Reverse-Transcription PCR, etc.), etc.

The present invention also provides for pharmaceutical compositions comprising an effective amount of a PTM or a nucleic acid encoding a PTM, and a pharmaceutically acceptable carrier. In a specific embodiment, the term "pharmaceutically acceptable" means approved by a regulatory agency ofthe Federal or a state government or listed in the U.S. Pharmacopeia or other generally recognized pharmacopeia for use in animals, and more particularly in humans. The term "carrier" refers to a diluent, adjuvant, excipient, or vehicle with which the therapeutic is administered. Examples of suitable pharmaceutical carriers are described in "Remington's Pharmaceutical sciences" by E.W. Martin, i a specific embodiment, it may be desirable to administer the pharmaceutical compositions ofthe invention locally to the area in need of treatment. This maybe achieved by, for example, and not by way of limitation, local infusion during surgery, topical application, e.g., in conjunction with a wound dressing after surgery, by injection, by means of a catheter, by means of a suppository, or by means of an implant, said implant being of a porous, non-porous, or gelatinous material, including membranes, such as sialastic membranes, or fibers. Other control release drug delivery systems, such as nanoparticles, matrices such as controlled-release polymers, hydrogels.

The PTM will be administered in amounts which are effective to produce the desired effect in the targeted cell. Effective dosages ofthe PTMs can be determined through procedures well known to those in the art which address such parameters as biological half-life, bioavailability and toxicity. The amount ofthe composition ofthe invention which will be effective will depend on the nature ofthe disease or disorder being treated, and can be determined by standard clinical techniques. In addition, in vitro assays may optionally be employed to help identify optimal dosage ranges.

The present invention also provides a pharmaceutical pack or kit comprising one or more containers filled with one or more ofthe ingredients ofthe pharmaceutical compositions ofthe invention optionally associated with such container(s) can be a notice in the form prescribed by a governmental agency regulating the manufacture, use or sale of pharmaceuticals or biological products, which notice reflects approval by the agency of manufacture, use or sale for human administration.

5.3.2. USE OF PTM MOLECULES FOR EXON TAGGING

In view of current efforts to sequence and characterize the genomes of humans and other organisms, there is a need for methods that facilitate such characterization. A majority ofthe information currently obtained by genomic mapping and sequencing is derived from complementary DNA (cDNA) libraries, which are made by reverse transcription of mRNA into cDNA. Unfortunately, this process causes the loss of information concerning intron sequences and the location of exon/intron boundaries.

The present invention encompasses a method for mapping exon-intron boundaries in pre-mRNA molecules comprising (i) contacting a pre-trans-splicing molecule with a pre-mRNA molecule under conditions in which a portion ofthe pre- trans-splicing molecule is trans-spliced to a portion ofthe target pre-mRNA to form a chimeric mRNA; (ii) amplifying the chimeric mRNA molecule; (iii) selectively purifying the amplified molecule; and (iv) deteimining the nucleotide sequence ofthe amplified molecule thereby identifying the intron-exon boundaries.

In an embodiment ofthe present invention, PTMs can be used in trans- splicing reactions to locate exon-intron boundaries in pre-mRNAs molecules. PTMs for use in mapping of intron-exon boundaries have structures similar to those i described above in Section 5.1. Specifically, the PTMs contain (i) a target binding domain that is designed to bind to many pre-mRNAs: (ii) a 3' splice region that includes a branch point, pyrimidine tract and a 3' splice acceptor site, or a 5' splice donor site; (iii) a spacer region that separates the mRNA splice site from the target binding domain; and (iv) a tag region that will be trans-spliced onto a pre-mRNA. Alternatively, the PTMs to be used to locate exon-intron boundaries may be engineered to contain no target binding domain.

For puφoses of intron-exon mapping, the PTMs are genetically engineered to contain target binding domains comprising random nucleotide sequences. The random nucleotide sequences contain at least 15-30 and up to several hundred nucleotide sequences capable of binding and anchoring a pre-mRNA so that the spliceosome processing machinery ofthe nucleus can trans-splice a portion (tag or marker region) ofthe PTM to a portion ofthe pre-mRNA. PTMs containing short target binding domains, or containing inosines bind under less stringent conditions to the pre-mRNA molecules. In addition, strong branch point sequences and pyrimidine tracts serve to increase the non-specificity of PTM trans-splicing. The random nucleotide sequences used as target binding domains in the PTM molecules can be generated using a variety of different methods, including, but not limited to, partial digestion of DNA with restriction endonucleases or mechanical shearing ofthe DNA. The use of such random nucleotide sequences is designed to generate a vast array of PTM molecules with different binding activities for each target pre-mRNA expressed in a cell. Randomized libraries of oligonucleotides can be synthesized with appropriate restriction endonucleases recognition sites on each end for cloning into PTM molecules genetically engineered into plasmid vectors. When the randomized oligonucleotides are litigated and expressed, a randomized binding library of PTMs is generated.

In a specific embodiment ofthe invention, an expression library encoding PTM molecules containing target binding domains comprising random nucleotide sequences can be generated using a variety of methods which are well known to those of skill in the art. Ideally, the library is complex enough to contain PTM molecules capable of interacting with each target pre-mRNA expressed in a cell. By way of example, Figure 9 is a schematic representation of two forms of PTMs which can be utilized to map intron-exon boundaries. The PTM on the left is capable of non-specifically trans-splicing into a pre-mRNA 3' splice site, while the PTM on the right is capable of trans-splicing into a pre-mRNA 5' splice site. Trans-splicing between the PTM and the target pre-mRNA results in the production of a chimeric mRNA molecule having a specific nucleotide sequence "tag" on either the 3' or 5' end of an authentic exon.

Following selective purification, a DNA sequencing reaction is then perfoπned using a primer which begins in the tag nucleotide sequence ofthe PTM and proceeds into the sequence ofthe tagged exon. The sequence immediately following the last nucleotide ofthe tag nucleotide sequence represents an exon boundary. For identification of intron-exon tags, the trans-splicing reactions ofthe invention can be performed either in vitro or in vivo using methods well known to those of skill in the art. 5.3.3. USE OF PTM MOLECULES FOR IDENTIFICATION

OF PROTEINS EXPRESSED fN A CELL

In yet another embodiment ofthe invention, PTM mediated trans- splicing reactions can be used to identify previously undetected and unknown proteins expressed in a cell. This method is especially useful for identification of proteins that cannot be detected by a two-dimensional electrophoresis, or by other methods, due to inter alia the small size ofthe protein, low concentration ofthe protein, or failure to detect the protein due to similar migration patterns with other proteins in two- dimensional electrophoresis. The present invention relates to a method for identifying proteins expressed in a cell comprising (i) contacting a pre-trans-splicing molecule containing a random target binding domain and a nucleotide sequence encoding a peptide tag with a pre-mRNA molecule under conditions in which a portion ofthe pre-trans- splicing molecule is trans-spliced to a portion ofthe target pre-mRNA to form a chimeric mRNA encoding a fusion polypeptide or separating it by gel electrophoresis (ii) affinity purifying the fusion polypeptide; and (iii) deterrnining the amino acid sequence ofthe fusion protein.

To identify proteins expressed in a cell, the PTMs ofthe invention are genetically engineered to contain: (i) a target binding domain comprising randomized nucleotide sequences; (ii) a 3' splice region that includes a branch point, pyrimidine tract and a 3' splice acceptor site and/or a 5' splice donor site; (iii) a spacer region that separates the PTM splice site from the target binding domain; and (iv) nucleotide sequences encoding a marker or peptide affinity purification tag. Such peptide tags include, but are not limited to, HIS tags (6 histidine consecutive residues) (Janknecht, et al., 1991 Proc. Natl. Acad. Sci. USA 88:8972-8976), glutathione-S-transferase (GST) (Smith, D.B. and Johnson K.S., 1988, Gene 67:31) (Pharmacia) or FLAG (Kodak/IBI) tags (Nisson, J. et al. J. Mol. Recognit., 1996, 5:585-594).

Erans-splicing reactions using such PTMs results in the generation of chimeric mRNA molecules encoding flision proteins comprising protein sequences normally expressed in a cell linked to a marker or peptide affinity purification tag.

The desired goal of such a method is that every protein synthesized in a cell receives a marker or peptide affinity tag thereby providing a method for identifying each protein expressed in a cell.

In a specific embodiment ofthe invention, PTM expression libraries encoding PTMs having different target binding domains comprising random nucleotide sequences are generated. The desired goal is to create a PTM expression library that is complex enough to produce a PTM capable of binding to each pre- mRNA expressed in a cell. In a preferred embodiment, the library is cloned into a mammalian expression vector that results in one, or at most, a few vectors being present in any one cell. To identify the expression of chimeric proteins, host cells are transformed with the PTM library and plated so that individual colonies containing one PTM vector can be grown and purified. Single colonies are selected, isolated, and propagated in the appropriate media and the labeled chimeric protein exon(s) fragments are separated away from other cellular proteins using, for example, an affinity purification tag. For example, affinity chromatography can involve the use of antibodies that specifically bind to a peptide tag such as the FLAG tag. Alternatively, when utilizing HIS tags, the fusion proteins are purified using a Ni²⁺ nitriloacetic acid agarose columns, which allows selective elution of bound peptide eluted with imidazole containing buffers. When using GST tags, the fusion proteins are purified using glutathione-S-transferase agarose beads. The fusion proteins can then be eluted in the presence of free glutathione.

Following purification ofthe chimeric protein, an analysis is carried out to determine the amino acid sequence ofthe fusion protein. The amino acid sequence ofthe fusion protein is determined using techniques well known to those of skill in the art, such as Edman Degradation followed by amino acid analysis using HPLC, mass spectrometry or an amino acid analyzation. Once identified, the peptide sequence is compared to those sequences available in protein databases, such as GenBank. If the partial peptide sequence is already known, no further analysis is done. If the partial protein sequence is unknown, then a more complete sequence of that protein can be carried out to determine the full protein sequence. Since the fusion protein will contain only a portion ofthe full length protein, a nucleic acid encoding the full length protein can be isolated using conventional methods. For example, based on the partial protein sequence oligonucleotide primers can be generated for use as probes or PCR primers to screen a cDNA library.

6. EXAMPLE: PRODUCTION OF ER-4NS-SPLICING MOLECULES The following section describes the production of PTMs and the demonstration that such molecules are capable of mediating trαns-splicing reactions resulting in the production of chimeric mRNA molecules.

6.1. MATERIALS AND METHODS

6.1.1. CONSTRUCTION OF PRE-mRNA MOLECULES Plasmids containing the wild type diphtheria toxin subunit A

(DT-A, wild-type accession #K01722) and a DT-A mutant (CRM 197, no enzymatic activity) were obtained from Dr. Virginia Johnson, Food and Drug Administration, Bethesda, Maryland (Uchida et al, 1973 J. Biol. Chem 248:3838). For in vitro experiments, DT-A was amplified using primers: DT-1F (5'- GGCGCTGCAGGGCGCTGATGATGTTGTTG); and DT-2R (5'-GGCGAAG CTTGGATCCGACACGATTTCCTGCACAGG), cut with Pstl and HindEI, and cloned into Pstl and HindUI digested pBS(-) vector (Stratagene, La Jolla, CA). The resulting clone, pDTA was used to construct the individual PTMs. (1) pPTM+: Targeted construct. Created by inserting IN3-1 (5'AATTCTCTAGATGCTT CACCCGGGCCTGACTCGAGTACTAACTGGTACCTCTTCTTTTTTTTCCTGCA ) and 1N2-4 (5'-GGAAAAAAAAGAAGAGGTACCAGTTAGTACTCGAGTCAGG CCCGGGTGAAGCATCTAGAG) primers into EcoRI and Pstl digested pDTA. (2) pPTM+Sp: As pPTM+ but with a 30 bp spacer sequence between the BD and BP. Created by digesting pPTM+ with Xhol and ligating in the oligonucleotides, spacer S (5'-TCGAGCAACGTTATAATAATGTTC) and spacer AS (5'-

TCGAGAACATTATT ATAACGTTGC). For in vivo studies, an EcoRI and HindUI fragment of pcPTM+Sp was cloned into mammalian expression vector pcDNA3.1 (Invitrogen), under the control of a CMV promoter. Also, the methionine at codon 14 was changed into isoleucine to prevent initiation of translation. The resulting plasmid was designated as pcPTM+Sp. (3) pPTM+CRM: As pPTM+Sp but the wild type DT-A was substituted with CRM mutant DT-A (T. Uchida, et al., 1973, J. Biol. Chem. 248:3838). This was created by PCR amplification of a DT-A mutant (mutation at G52E) using primers DT-1F and DT-2R. For in vivo studies, an EcoRI HindUI fragment of PTM+CRM was cloned into pc3.1DNA that resulted in pcPTM+ARM. (4) PTM-: Non-targeted construct. Created by digestion of PTM+ with EcoRI and Pst I, gel purified to remove the binding domain followed by ligation of the oligonucleotides, IN-5 (5'-ATCTCTAGATCAGGCCCGGGTGAAGCC CGAG) and IN-6 (5'-TGCTTCACCC GGGCCTGATCTAGAG). (5) PTM-Sp, is an identical version ofthe PTM-, except it has a 30 bp spacer sequence at the Pstl site. Similarly, the splice mutants [Py(-)AG(-) and BP(-)Py(-)AG(-)] and safety variants [PTM+SF-Pyl, PTM+SF-Py2, PTM+SFBP3 and PTM+SFBP3-Pyl] were constructed either by insertion or deletion of specific sequences (see 1).

Nucleotides in bold indicate the mutations compared to normal BP, PPT and 3' splice site. Branch site A is underlined. The nucleotides in italics indicates the mismatch introduced into safety BD to mask the BP sequence in the PTM. A double-trans-splicing PTM construct (DS-PTM) was also made adding a 5' splice site and a second target binding domain complementary to the second intron of βHCG pre-mRNA to the 3' end ofthe toxin coding sequence of PTM+SF (Figure A).

6.1.2. BHCG6 TARGET PRE-mRNA

To produce the in vitro target pre-mRNA, a Sad fragment of βHCG gene 6 (accession #X00266) was cloned into pBS(-). This produced an 805 bp insert from nucleotide 460 to 1265, which includes the 5' untranslated region, initiation codon, exon 1, intron 1, exon 2, and most of intron 2. For in vivo studies, an EcoRI and BamHI fragment was cloned into mammalian expression vector (pc3.IDNA), producing βHCG6.

6.1.3. mRNA PREPARATION

For in vitro splicing experiments, βHCG6, β-globin pre-mRNA and different PTM mRNAs were synthesized by in vitro transcription of BamHI and HindUI digested plasmid DNAs respectively, using T7 mRNA polymerase (Pasman & Garcia-Blanco, 1996, Nucleic Acids Res. 24:1638). Synthesized mRNAs were purified by electrophoresis on a denaturing polyacrylamide gel, and the products were excised and eluted.

6.1.4 IN VITRO SPLICING PTMs and target pre-mRNA were annealed by heating at 98 ° C followed by slow cooling to 30-34 °C. Each reaction contained 4 μl of annealed mRNA complex (100 ng of target and 200 ng of PTM), IX splice buffer (2 mM MgCl₂, 1 mM ATP, 5 mM creatinine phosphate, and 40 mM KCI) and 4 μl of HeLa splice nuclear extract (Promega) in a 12.5 μl final volume. Reactions were incubated at 30°C for the indicated times and stopped by the addition of an equal volume of high salt buffer (7 M urea, 5% SDS, 100 mM LiCl, 10 mM EDTA and 10 mM TrisHCI, pH 7.5). Nucleic acids were purified by extraction with phenol:chloroform:isoamyl alcohol (50:49: 1) followed by ethanol precipitation. 6.1.5. REVERSE TRANS CRLPTION-PCR REACTIONS

RT-PCR analysis was performed using EZ-RT PCR kit (Perkin-Elmer, Foster City, CA). Each reaction contained 10 ng of czs- or trαns-spliced mRNA, or 1-2 μg of total mRNA, 0.1 μl of each 3' and 5' specific primer, 0.3 mM of each dNTP, IX EZ buffer (50 mM bicine, 115 mM potassium acetate, 4% glycerol, pH 8.2), 2.5 mM magnesium acetate and 5 U of xTth DNA polymerase in a 50 μl reaction volume. Reverse transcription was performed at 60°C for 45 min followed by PCR amplification ofthe resulting cDNA as follows: one cycle of initial denaturation at 94°C for 30 sec, and 25 cycles of denaturation at 94°C for 18 sec and annealing and extension at 60°C for 40 sec, followed by a 7 min final extension at 70°C. Reaction products were separated by electrophoresis in agarose gels.

Primers used in the smdy were as follows: DT-1F: GGCGCTGCAGGGCGCTGATGATGTTGTTG DT-2R: GGCGAAGCTTGGATCCGACACGATTTCCTGCACAGG DT-3R: CATCGTCATAATTTCCTTGTG DT-4R: ATGGAATCTACATAACCAGG DT-5R: GAAGGCTGAGCACTACACGC HCG-R2: CGGCACCGTGGCCGAAGTGG, Bio-HCG-F: ACCGGAATTCATGAAGCCAGGTACACCAGG β-globulin-F: GGGCAAGGTGAACGTGGATG β-globulin-R: ATCAGGAGTGGACAGATCC

6.1.6. CELL GROWTH. TRANSFECTION AND mRNA ISOLATION

Human lung cancer cell line H1299 (ATCC accession # CRL-5803) was grown in RPMI medium supplemented with 10% fetal bovine serum at 37°C in a 5% CO₂ environment. Cells were transfected with pcSp+CRM (CRM is a nonfunctional toxin), a vector expressing a PTM, or vector alone (pcDNA3.1) using lipofectamine reagent (Life Technologies, Gaithersburg, MD). The assay was scored for neomycin resistance (neo¹) colony formation two weeks after transfection. Four neo^r colonies were selected and expanded under continued neo selection. Total cellular mRNA was isolated using RNA exol (BioChain Institute, Inc., San Leandro, CA) and used for RT-PCR.

6.1.7. ER-4NS-SPLICING IN TUMORS IN NUDE MICE

Eleven nude mice were bilaterally injected (except BIO, Bl 1 and B12 had 1 tumor) into the dorsal flank subcutaneous space with 1 x 10⁷ HI 299 human lung tumor cells (day 1). On day 14, the mice were given an appropriate dose of anesthesia and injected with, or without electroporation (T820, BTX Inc., San Diego, CA) in several orientations with a total volume of 100 μl of saline containing 100 μg pcSp+CRM with or without pcβHCG6 or pcPTM+Sp. Solutions injected into the right side tumors also contained India ink to mark needle tracks. The animals were sacrificed 48 hours later and the tumor excised and immediately frozen at -80 °C. For analysis, 10 mg of each tumor was homogenized and mRNA was isolated using a Dynabeads mRNA direct kit (Dynal) following the manufacturers directions. Purified mRNA (2 μl of 10 μl total volume) was subjected to RT-PCR using βHCG-F and DT- 5R primers as described earlier. All samples were re-amplified using DT-3R, a nested DT-A primer and biotinylated βHCG-F and the products were analyzed by electrophoresis on a 2% agarose gel. Samples that produced a band were processed into single stranded DNA using M280 Streptavidin Dynabeads and sequenced using a toxin specific primer (DT-3R).

, 6.2. RESULTS

6.2.1. SYNTHESIS OF PTM

A prototypical trans-splicing mRNA molecule, pcPTM+Sp (Figure IA) was constructed that included: an 18 nt target binding domain (complementary to βHCG6 intron 1), a 30 nucleotide spacer region, branch point (BP) sequence, a polypyrimidine tract (PPT) and an AG dinucleotide at the 3' splice site immediately upstream of an exon encoding diphtheria toxin subunit A (DT-A) (Uchida et al, 1973, J. Biol. Chem. 248:3838). Later DT-A exons were modified to eliminate translation initiation sites at codon 14. The PTM constructs were designed for maximal activity in order to demonstrate trans-splicing; therefore, they included potent 3' splice elements (yeast BP and a mammalian PPT) (Moore et al, 1993, In The mRNA World, R.F. Gesteland and J.F. Atkins, eds. (Cold Spring Harbor, New York: Cold Spring Harbor Laboratory Press). βHCG6 pre-mRNA (Talmadge et al, 1984, Nucleic Acids Res. 12:8415) was chosen as a model target as this gene is expressed in most tumor cells. It is not expressed in normal adult cells, with the exception of some in the pituitary gland and gonads. (Acevedo et al, 1992, Cancer 76:1467; Hoon et al, 1996, hit J. Cancer 69:369; Belief et ah, 1997, Cancer Res. 57:516). As shown in Figure IC, pcPTM+Sp forms conventional Watson-Crick base pairs by its binding domain with the 3' end of βHCG6 intron 1, masking the intronic 3' splice signals of the target. This feature is designed to facilitate trans-splicing between the target and the PTM.

HeLa nuclear extracts were used in conjunction with established splicing procedures (Pasman & Garcia-Blanco, 1996, Nucleic Acids Res. 24:1638) to test if a PTM constract could invade the βHCG6 pre-mRNA target. The products of in vitro trans-splicing were detected by RT-PCR, using primers specific for chimeric mRNA molecules. The predicted product of a successful trαns-splicing reaction is a chimeric mRNA comprising the first exon of βHCG6, followed immediately by the exon contributed from pcPTM+Sp encoding DT-A (Figure IC). Such chimeric mRNAs were readily detected by RT-PCR using primers βHCG-F (specific to βHCG6 exon 1) and DT-3R (specific to DT-A, Figure 2A, lanes 1-2). At time zero or in the absence of ATP, no 466 bp product was observed, indicating that this reaction was both ATP and time dependent.

The target binding domain of pcPTM+Sp contained 18 nucleotides complementary to βHCG6 intron 1 pre-mRNA and demonstrated efficient trαns- splicing (Figure 2A, lanes 1-2). Erans-splicing efficiency decreased at least 8 fold (Figure 2, lanes 3-4) using non-targeted PTM-Sp, which contains a non- complementary 18 nucleotide "non-binding domain". Erans-splicing efficiencies of PTM mRNAs with or without a spacer between the binding domain and BP were also compared. This experiment demonstrated a significant increase in the efficiency of trαns-splicing by the addition of a spacer (Figure 2B, lanes 2 + 5). To facilitate the recruitment of splicing factors required for efficient trαns-splicing, some space may be needed between the 3' splice site and the double-stranded secondary stracture produced by the binding domain/target interaction.

To investigate the effect of PTM length on trαns-splicing specificity, shorter PTMs were synthesized from Accl cut PTM plasmid (see Figure 1). This eliminated 479 nt from the 3' end ofthe DT-A coding sequence. Figure 2B shows the trans-splicing ability of a targeted short PTM(+) (lanes 10-12), compared to anon- targeted short PTM(-) (lanes 14-17). Short PTM+ produced substantially more trans- spliced product (Figure 2B, lane 12) than its counteφart, non-targeted short PTM (Figure 2B, lane 17). These experiments indicate that longer PTMs may have increased potential to mediate trαns-splicing non-specifically.

6.2.2. ACCURACY OF PTM SPLICEOSOME

MEDIATED ER.4NS-SPLICING

To confirm that trans-splicing between the pcPTM+Sp and βHCG6 target is precise, RT-PCR amplified product was produced using 5' biotinylated βHCG-F and nonbiotinylated DT-3R primers. This product was converted into single stranded DNA and sequenced directly with primer DT-3R (DT-A specific reverse primer) using the method of Mitchell and Merril (1989, Anal. Biochem. 178:239). Erαns-splicing occurred exactly between the predicted splice sites (Figure 3), confirming that a conventional pre-mRNA can be invaded by an engineered PTM construct during splicing; moreover, this reaction is precise.

In addition selective trans-splicing of a double splicing PTM (DS- PTM) was observed (Figure 8B). The DS-PTM can produce trans-splicing by contributing either a 3' or 5' splice site. Further, DS-PTMs can be constructed which will be capable of simultaneously double-trαns-splicing, at both a 3' and 5' site, thereby permitting exon replacement. Figure 8B demonstrates that in this construct the 5' splice site is most active at a 1:1 concentration of target βHCG pre-mRNA:DS- PTM. At a 1 :6 ratio the 3' splice site is more active. 6.2.3. 3' SPLICE SITES ARE ESSENTIAL FOR PTM ER NS-SPLICING

In general, the 3' splice site contains three elements: 1) a BP sequence located 5' ofthe acceptor site, 2) a PPT consisting of a short run of pyrimidine residues, and 3) a YAG trinucleotide splice site acceptor at the intron-exon border (Senapathy et al, 1990, Cell 91:875; Moore et al, 1993). Deletion or alteration of one of these sequence elements are known to either decrease or abolish splicing (Aebi et al, 1986; Reed & Maniatis 1988, Genes Dev. 2:1268; Reed, 1989, Genes Dev. 3:2113; Roscigno etal, 1993, J. Biol. Chem. 268:11222; Coolidge et al, 1997, Nucleic Acids Res. 25:888). The role of these conserved elements in targeted trans- splicing was addressed experimentally. In one case [(BP(-)Py(-)AG(-)], all three cis - elements (BP, PPT and AG dinucleotide) were replaced by random sequences. A second splicing mutant [(Py(-)AG(-)] was constructed in which the PPT and the 3' splice site acceptor were mutated and substituted by random sequences. Neither constract was able to support trαns-splicing in vitro (Figure 2A, lanes 5-8), suggesting that, as in the case of conventional cts-splicing, the PTM trans-splicing process also requires a functional BP, PPT and AG acceptor at the 3' splice site.

6.2.4. DEVELOPMENT OF A "SAFETY" SPLICE SITE TO INCREASE SPECIFICITY

To improve the levels of target specificity achieved by the inclusion of a binding domain or by shortening the PTM, the target-binding domain of several PTM constructs was modified to create an intra-molecular stem to mask the 3' splice site (termed a "safety PTM"). The safety stem is formed by portions ofthe binding domain that partially base pair with regions ofthe PTM 3' splice site or sequences adjacent to them, thereby blocking the access of spliceosomal components to the PTM 3' splice site prior to target acquisition (Figure 4A, PTM+SF). Base pairing between free portions ofthe PTM binding domain and βHCG6 target region unwinds the safety stem, allowing splicing factors such as U2AF to bind to the PTM 3' splice site and initiate trans-splicing (Figure 4B).

This concept was tested in splicing reactions containing either PTM+SF (safety) or pcPTM+Sp (linear), and both target (βHCG6) and non-target (β- globin) pre-mRNA. The spliced products were subsequently analyzed by RT-PCR and gel electrophoresis. Using βHCG-F and DT-3R primers, the specific 196 bp trans-spliced band was demonstrated in reactions containing βHCG target and either linear PTM (pcPTM+Sp, Figure 5, lane 2) or safety PTM (PTM+SF, Figure 5, lane 8). Comparison of the targeted trans-splicing between linear PTM (Figure 5, lane 2) and safety PTM (Figure 5, lane 8) demonstrated that the safety PTM trans-spliced less efficiently than the linear PTM.

Non-targeted reactions were amplified using β-globin-F (specific to exon 1 of β-globin) and DT-3R primers. The predicted product generated by non- specific PTM trαns-splicing with β-globin pre-mRNA is 189 bp. Non-specific trαns- splicing was evident between linear PTM and β-globin pre-mRNA (Figure 5, lane 5). In contrast, non-specific trans-splicing was virtually eliminated by the use of safety PTM (Figure 5, lane 11). This was not unexpected, since the linear PTM was designed for maximal activity to prove the concept of spliceosome-mediated trans- splicing. The open structure ofthe linear PTM combined with its potent 3' splice sites strongly promotes the binding of splicing factors. Once bound, these splicing factors can potentially initiate trans-splicing with any 5' splice site, in a process similar to trαns-splicing in trypanosomes. The safety stem was designed to prevent splicing factors, such as U2AF from binding to the PTM prior to target acquisition. This result is consistent with a model that base-pairing between the free portion ofthe binding domain and the βHCG6 target unwinds the safety stem (by mRNA-mRNA interaction), uncovering the 3' splice site, permitting the recruitment of splicing factors and initiation of trans-splicing. No trans-splicing was detected between β- globin and βHCG6 pre-mRNAs (Figure 5, lanes 3, 6, 9 and 12).

6.2.5. EN VITRO iNS-SPLICIΝG OF SAFETY PTM AND VARIANTS

To better understand the role of c/s-elements at the 3' splice site in trans-splicing a series of safety PTM variants were constructed in which either the PPT was weakened by substitution with purines and or the BP was modified by base substitution (see Table I). In vitro trans-splicing efficiency ofthe safety (PTM+SF) was compared to three safety variants, which demonstrated a decreased ability to trans-splice. The greatest effect was observed with variant 2 (PTM+SFPy2), which was trans-splicing incompetent (Figure 4C, lanes 5-6). This inhibition of trans- splicing may be attributed to a weakened PPT and/or the higher T_m ofthe safety stem. In contrast, variations in the BP sequence (PTM+SFBP3) did not markedly effect trαns-splicing (Figure 4C, lanes 7-8). This was not s prising since the modifications introduced were within the mammalian branch point consensus range YNYURAC (where Y = pyrimidine, R = purine and N = any nucleotide) (Moore et al., 1993). This finding indicates that the branch point sequence can be removed without affecting splicing efficiency. Alterations in the PPT (PTM+SF-Pyl) decreased the level of trans -splicing (lanes 3-4). Similarly, when both BP and PPT were altered PTM+SFBP3-Pyl, they caused a further reduction in trans-splicing (Figure 4C, lanes 9-10). The order of trαns-splicing efficiency of these safety variants is PTM+SF>PTM+SFBP3> PTM+SFPyl>PTM+SFBP3-Pyl>PTM+SFPy2. These results confirm that both the PPT and BP are important for efficient in vitro trans- splicing (Roscigno et al, 1993, J. Biol. Chem. 268 : 11222).

6.2.6. COMPETITION BETWEEN CIS- AND TRANS- SPLICING

To determine if it was possible to block pre-mRNA cts-splicing by increasing concentrations of PTM, experiments were performed to drive the reaction towards trαns-splicing. Splicing reactions were conducted with a constant amount of βHCG6 pre-mRNA target and various concentrations of trαns-splicing PTM. Cts- splicing was monitored by RT-PCR using primers to βHCG-F (exon 1) and βHCG-R2 (exon 2). This amplified the expected 125 bp czs-spliced and 478 bp unspliced products (Figure 6A). The primers βHCG-F and DT-3R were used to detect trans- spliced products (Figure 6B). At lower concentrations of PTM, czs-splicing (Fig. 6A, lanes 1-4) predominated over trαns-splicing (Figure 6B, lanes 1-4). Czs-splicing was reduced approximately by 50% at a PTM concentration 1.5 fold greater than target. Increasing the PTM mRNA concentration to 3 fold that of target inhibited cts-splicing by more than 90% (Figure 6A, lanes 7-9), with a concomitant increase in the trans- spliced product (Figure 6B, lanes 6-10). A competitive RT-PCR was performed to simultaneously amplify both cis and trans-spliced products by including all three primers (βHCG-F, HCG-R2 and DT-3R) in a single reaction. This experiment had similar results to those seen in Figure 6, demonstrating that under in vitro conditions, a PTM can effectively block target pre-mRNA cts-splicing and replace it with the production of an engineered trans-spliced chimeric mRNA.

6.2.7. ΩMNS-SPLICING 3N TISSUE CULTURE

To demonstrate the mechanism of trαns-splicing in a cell culture model, the human lung cancer line H1299 (βHCG6 positive) was transfected with a vector expressing SP+CRM (a non-functional diphtheria toxin) or vector alone (pcDNA3.1) and grown in the presence of neomycin. Four neomycin resistant colonies were individually collected after 14 days and expanded in the continued presence of neomycin. Total mRNA was isolated from each clone and analyzed by RT-PCR using primers βHCG-F and DT-3R. This yielded the predicted 196 bp trαns- spliced product in three out ofthe four selected clones (Figure 7A, lanes 2, 3 and 4). The amplified product from clone #2 was directly sequenced, confirming that PTM driven trαns-splicing occurred in human cells exactly at the predicted sphce sites of endogenously expressed βHCG6 target exon 1 and the first nucleotide of DT-A (Figure 7B).

^• 6.2.8. ER NS-SPLICING IN AN IN VIVO MODEL

To demonstrate the mechanism of trαns-splicing in vivo, the following experiment was conducted in athymic (nude) mice. Tumors were established by injecting 10⁷ HI 299 cells into the dorsal flank subcutaneous space. On day 14, PTM expression plasmids were injected into tumors. Most tumors were then subjected to electroporation to facilitate plasmid delivery (see Table 2, below). After 48 hrs, tumors were removed, poly-A mRNA was isolated and amplified by RT-PCR. Trans- splicing was detected in 8 out of 19 PTM treated tumors. Two samples produced the predicted trans-spliced product (466 bp) from mRNA after one round of RT-PCR. Six additional tumors were subsequently positive for trans-splicing by a second PCR amplification using a nested set of primers that produced the predicted 196 bp product (Table 2). Each positive sample was sequenced, demonstrating that βHCG6 exon 1 was precisely trans-spliced to the coding sequence of DT-A (wild type or CRM mutant) at the predicted splice sites. Six ofthe positive samples were from treatment groups that received cotransfected plasmids, pcPTM+CRM and pcHCG6, which increased the concentration of target pre-mRNA. This was done to enhance the probability of detecting trαns-spliced events. The other two positive tumors were from a group that received only pcPTM+Sp (wild type DT-A). These tumors were not transfected with βHCG6 expression plasmid, demonstrating once again, as in the tissue culture model described in Section 6.2.7, that trαns-splicing occurred between the PTM and endogenous βHCG6 pre-mRNA produced by tumor cells.

: 6 pulses of 99μs sets of 3 pulses administered orthogonally ^b: 8 pulses of 10ms sets of 4 pulses administered orthogonally ^c: 8 pulses of 50ms sets of 4 pulses administered orthogonally ⁺: positive for RT-PCR trans-spliced produce : (Sid not receive electroporation

7. EXAMPLE: lacL ER^NS-SPLICING MODEL

In order to demonstrate and evaluate the generality ofthe mechanism of spliceosome mediated targeted trans-splicing between a specific pre-mRNA target

10 and a PTM, a simple model system based on expression of enzyme β-galactosidase was developed. The following section describes results demonstrating successful splicesome mediated targeted trans-splicing between a specific target and a PTM. 7.1. MATERIALS AND METHODS

7.1.1. PRIMER SEQUENCES

The following primers were used for testing the lacZ model system: 5' Lac-IF GCATGAATTCGGTACCATGGGGGGGTTCTCATCATCATC

5' Lac-IR CTGAGGATCCTCTTACCTGTAAACGCCCATACTGAC

3' Lac-IF GCATGGTAACCCTGCAGGGCGGCTTCGTCTGGGACTGG 3' Lac-lR

CTGAAAGCTTGTTAACTTATTATTTTTGACACCAGACC

3' Lac-Stop GCATGGTAACCCTGCAGGGCGGCTTCGTCTAATAATGGGACTGGGT G HCG-frilF

GCATGGATCCTCCGGAGGGCCCCTGGGCACCTTCCAC

HCG-InlR CTGACTGCAGGGTAACCGGACAAGGACACTGCTTCACC HCG-Ex2F GCATGGTAACCCTGCAGGGGCTGCTGCTGTTGCTG

HCG-Ex2R CTGAAAGCTTGTTAACCAGCTCACCATGGTGGGGCAG

Lac-TRl (Biotin): 7-GGCTTTCGCTACCTGGAGAGAC Lac-TR2 GCTGGATGCGGCGTGCGGTCG HCG-R2: CGGCACCGTGGCCGAAGTGG

1. 1.2. CONSTRUCTION OF THE lacZ PRE-mRNA TARGET MOLECULE

The lacZ target 1 pre-mRNA (pc3.1 lacTl) was constructed by cloning ofthe following three PCR products: (i) the 5' fragment of lacZ; followed by (ii) βHCG6 intron 1; (iii) and the 3' fragment of lacZ. The 5' and 3' fragment ofthe lacZ gene were PCR amplified from template pcDNA3.1/His/lacZ (IhvitiOgen,San Diego, CA) using the following primers: 5' Lac-IF and 5'Lac-lR (for 5' fragment), and 3'Lac-lF and 3' Lac-IR (for 3' fragment). The amplified lacZ 5' fragment is 1788 bp long which includes the initiation codon, and the amplified 3' fragment is 1385 bp long and has the natural 5' and 3' splice sites in addition to a branch point, polypyrimidine tract and βHCG6 intron 1. The βHCG6 intron 1 was PCR amplified using the following primers: HCG-InlF and HCG-frilR.

The lacZ target 2 is an identical version of lacZ target 1 except it contains two stop codons (TAA TAA) in frame four codons after the 3 'splice site. This was created by PCR amplification ofthe 3' fragment (lacZ) using the following primers: 3' Lac-Stop and 3' Lac IR and replacing the functional 3' fragment in lacZ target 1.

7.1.3. CONSTRUCTION OF pc3.1 PTM1 and pc3.1 PTM2

The pre-trans-splicing molecule, pc3.1 PTM1 was created by digesting pPTM +Sρ with Pstl and HindlH and replacing the DNA fragment encoding the DT- A toxin with the a DNA fragment encoding the functional 3' end of lacZ. This fragment was generated by PCR amplification using the following primers: 3' Lac-IF and 3' Lac-IR. For cell culture experiments, an EcoRI and HindUI fragment of pc3.1 PTM2 which contains the binding domain to HCG intron 1, a 30 bp spacer, a yeast branch point (TACTAAC), and strong polypyrimidine tract followed by the lacZ cloned was cloned into pcDNA3.1.

The pre-trans-splicing molecule, pc3.1 PTM2 was created by digesting pPTM +Sp with Pstl and HindUI and replacing the DNA fragment encoding the DT- A toxin with the βHCG6 exon 2. βHCG6 exon 2 was generated by PCR amplification using the following primers: HCG-Ex2F and HCG-Ex2R. For cell culture experiments, an EcoRI and Hindlll fragment of pc3.1 PTM2 which contains the binding domain to HCG intron 1, a 30 bp spacer, a yeast branch point (TACTAAC), and strong polypyrimidine tract followed by the βHCG6 exon 2 cloned was used. 7.1.4. CO-TRANSFECTION OF THE lacZ SPLICE TARGET

PRE-mRNA AND PTMS INTO 293T CELLS

Human embryonic kidney cells (293T) were grown in DMEM medium supplemented with 10% FBS at 37°C in a 5% CO₂. Cells were co-transfected with pc3.1 LacT 1 and ρc3.1 PTM2, or pc3.1 LacT2 and ρc3.1 PTMl , using Lipofectamine Plus (Life Technologies,Gaithersburg, MD) according to the manufacturer's instructions. 24 hours post-transfection, the cells were harvested; total RNA was isolated and RT-PCR was performed using specific primers for the target and PTM molecules, β-galactosidase activity was also monitored by staining the cells using a β-gal staining kit (Invitrogen, San Diego. CA).

7.2. RESULTS

7.2.1. THE lacZ SPLICE TARGET CIS-SPLICES EFFICIENTLY TO PRODUCE FUNCTIONAL β-GALACTOSIDASE

To test the ability ofthe splice target pre-mRNA to cts-splice efficiently, pc3.1 lacTl was transfected into 293 T cells using Lipfecta ine Plus reagent (Life Technologies,Gaithersburg, MD) followed by RT-PCR analysis of total RNA. Sequence analysis ofthe czs-spliced RT-PCR product indicated that splicing was accurate and occurred exactly at the predicted splice sites (Fig. 12B). In addition, accurate cis-splicing ofthe target pre-mRNA molecule results in formation of a mRNA capable of encoding active β-galactosidase which catalyzes the hydrolysis of β-galactosidase, i.e., X-gal, producing a blue color that can be visualized under a microscope. Accurate czs-splicing ofthe target pre-mRNA was further confirmed by successfully detecting β-galactosidase enzyme activity.

Repair of defective lacZ target 2 pre-mRNA by trans-splicing ofthe functional 3' lacZ fragment (PTMl) was measured by staining for β-galactosidase enzyme activity. For this puφose, 293T cells were co-transfected with lacZ target 2 pre-mRNA (containing a defective 3' fragment) and PTMl (contain normal 3' lacZ sequence). 48 hours post-transfection cells were assayed for β-galactosidase enzyme activity. Efficient trans-splicing of PTMl into the lacZ target 2 pre-mRNA will result in the production of functional β-galactosidase activity. As demonstrated in Figure 11B-E, trans-splicing of PTM 1 into lacZ target 2 results in restoration of β- galactosidase enzyme activity up to 5% to 10% compared to control.

7.2.2. TARGETED ER_4NS-SPLIC1NG BETWEEN THE lacZ TARGET PRE-mRNA and PTM2

To assay for trans-splicing, lacZ target pre-mRNA and PTM2 were transfected into 293 T cells. Following transfection, total RNA was analyzed using RT-PCR. The following primers were used in the PCR reactions: /αcZ-TRl (lacZ 5' exon specific) and HCGR2 (βHCGR exon 2 specific). The RT PCR reaction produced the expected 195 bp trans-spliced product ( Fig. 11, lanes 2 and 3) demonstrating efficient trαns-splicing between the lacZ target pre-mRNA and PTM 2. Lane 1 represents the control, which does not contain PTM 2.

The efficiency ofthe trαns-splicing was also measured by staining for β-galactosidase enzyme activity. To assay for trans-splicing, 293T cells were co- transfected with lacZ target pre-mRNA and PTM 2. 24 hours post-transfection, cells were assayed for β-galactosidase activity. If there is efficient trans-splicing between the target pre-mRNA and the PTM, a chimeric mRNA is produced consisting ofthe 5' fragment ofthe lacZ target pre-mRNA and βHCG6 exon 2 is formed which is incapable of coding for an active β-galactosidase. Results from the co-transfection experiments demonstrated that trans-splicing of PTM2 into lacZ target 1 resulted in the reduction of β-galactosidase activity by compared to the control.

To further confirm that trans-splicing between the lacZ target pre- mRNA and PTM2 is accurate, RT-PCR was performed using 5' biotinylated lacZ- TR1 and non-biotinylated HCGR2 primers. Single stranded DNA was isolated and sequenced directly using HCGR2 primer (HCG exon 2 specific primer). As evidenced by the sequence ofthe splice junction, trαns-splicing occurred exactly as predicted between the splice sites (Fig. 12A and 12B), confirming that a conventional pre-mRNA can be invaded by an engineered PTM during splicing, and moreover, that this reaction is precise. 8. EXAMPLE: CORRECTION OF THE CYSTIC FIBROSIS

TRANSMEMBRANE REGULATOR GENE

Cystic fibrosis (CF) is one ofthe most common genetic diseases in the world. The gene associated with CF has been isolated and its protein product deduced (Kerem, B.S. et al., 1989, Science 245:1073-1080; Riordan et al., 1989, Science 245:1066-1073 ;Rommans, et al., 1989, Science 245:1059-1065). The protein product ofthe CF associated gene is referred to as the cystic fibrosis transmembrane conductance regulator (CFTR). The most common disease-causing mutation which accounts for ~70% of all mutant alleles is a deletion of three nucleotides in exon 10 that encode for a phenylalanine at position 508 (ΔF508). The following section describes the successful repair ofthe cystic fibrosis gene using spliceosome mediated trans-splicing and demonstrates the feasibility of repairing CFTR in a model system.

8.1 MATERIALS AND METHODS

8.1.1. PRE-TRANS-SPLICING MOLECULE

The CFTR pre-trans-splicing molecule (PTM) consists of a 23 nucleotide binding domain complimentary to CFTR intron 9 (3¹ end, -13 to -31), a 30 nucleotide spacer region (to allow efficient binding of spliceosomal components), branch point (BP) sequence, polypyrintidine tract (PPT) and an AG dinucleotide at the 3' splice site immediately upstream ofthe sequence encoding CFTR exon 10 (wild type sequence containing F508). This initial PTM was designed for maximal activity in order to demonstrate trans-splicing; therefore the PTM included a UACUAAC yeast consensus BP sequence and an extensive PPT. An 18 nucleotide HIS tag (6 histamine codons) was included after wild type exon 10 coding sequence to allow specific amplification and isolation ofthe trans-spliced products and not the endogenous CFTR. The oligonucleotides used to generate the two fragments included unique restriction sites. (Apal and Pstl, and Pstl and Notl, respectively) to facilitate directed cloning of amplified DNA into the mammalian expression vector ρcDNA3.1. 8.1.2. THE TARGET CFTR PRE-mRNA MINI-GENE

The CFTR mini-gene target is shown in Figure 13 and consists of CFTR exon 9 ; the functional 5' and 3' regions of intron 9 (260 and 265 nucleotides from each end, respectively); exon 10 [ΔF508]; and the 5' region of intron 10 (96 5 nucleotides). In addition, as depicted in Figure 16, a mini-target gene comprising CFTR exons 1-9 and 10-24 can be used to test the use of spliceosome mediated trαns- splicing for correction of the cystic fibrosis mutation. Figure 17, shows a double splicing PTM that may also be used for correction ofthe cystic fibrosis mutation. As shown, the double splicing PTM contains CFTR BD intron 9, a spacer, a branch point, a polypyrimidine tract, a 3' splice site, CFTR exon 10, a spacer, a branch point, a polypyrimidine tract, a 5' splice site and CFTRBD exon 10.

8.1.3. OLIGONUCLEOTIDES

The following oligonucleotides were used to create CFTR PTM: Forward CF3 ACCT GGGCCC ACC CAT TAT TAG GTC ATT AT CCGCGG AAC ATT ATA

Apal site. Intron 9 CFTR, -12 to -34. Reverse CF4

ACCT CTGCAGGrG CC CTG CAG GAAAAAAAA GAAG Pstl. BstEI. PPT.

Forward CF5

ACCT CTGCAG ACT TCA CTT CTA ATG ATG AT Pstl. Exon 10 CFTR, +1 to +24

Reverse CF6 ACCT GCGGCCGC CT ATGATGATGATG TGATG CTC TTC TAG TTG GCA

TGC

Not I. Stop Polyhistamine tag Exon 10 CFTR, +15 to +132

The following nucleotides were used to create the CFTR TARGET pre-mRNA mini gene (Exon 9 + mini-intron 9 + Exon 10 + 5' end Intron 10): Forward CF18

GACCT CTCGAG GGA TTT GGG GAA TTA TTT GAG Xhol Exon 9 CFTR, 1 to 21.

Reverse CF19

CTGACCT GCGGCCGC TAG AGT GTT GAA TGT GGT GC Not! Intron 9 5' end.

Forward CF20 CTGACCT GCGGCCGC CCA ACT ATC TGA ATC ATG TG

Not! Intron 9 3' end.

Reverse CF21

GACCT CTTAAGTAGACT AAC CGATTG A ATG Aflll Intron 10 5' end. The following oligonucleotides were used for detection of trans-spliced products: Reverse Bio-His

CTA ATG ATG ATG ATG ATG ATG Stop. Polyhistidine tag (5' biotin label). Reverse Bio-His^

CGC CTA ATG ATG ATG ATG ATG 3' UT Stop. Polyhistidine tag (5' biotin label). Forward CF8

CTT CTT GGT ACT CCT GTC CTG Exon 9 CFTR.

Forward CF18

GACCT CTCGAG GGA TTT GGG GAA TTA TTT GAG Xhol. Exon 9 CFTR. Reverse CF28 AAC TAG AAG GCACAG TCG AGG

Pc3.1 vector sequence (present in PTM 3' UT but not target). 8.2. RESULTS

The PTM and target pre-mRNA were co-transfected in 293 embryonic kidney cells using lipofectamine (Life Technologies,Gaithersburg, MD). Cells were harvested 24 h post transfection and RNA was isolated. Using PTM and target- specific primers in RT-PCR reactions, a trans-spliced product was detected in which mutant exon 10 ofthe target pre-mRNA was replaced by the wild type exon 10 of the PTM (Figure 14). Sequence analysis ofthe trans-spliced product confirmed the restoration ofthe three nucleotide deletion and that splicing was accurate, occurring at the predicted splice sites (Figure 15), demonstrating for the first time RNA repair of the cystic fibrosis gene, CFTR (Mansfield et al., 2000, Gene Therapy 7: 1885-1895).

9. EXAMPLE: DOUBLE-E 4NS-SPLICING

The following example demonstrates accurate replacement of an internal exon by a double-trαns-splicing between a target pre-mRNA and a PTM RNA containing both 3' and 5' splice sites leading to production of full length functionally active protein.

As described herein, any pre-mRNA can be reprogrammed by providing a trans-reactive RNA molecule containing either a 3 '-splice site, a 5 '-splice site or both. The following example describes successful targeting and replacement of a single internal exon utilizing pre-trans-splicing molecules (PTMs) containing both the 5' and 3' splice sites. Such PTMs can promote two trans-splicing reactions with the intended target gene mediated by the splicesome(s). To test this mechanism, a splicing lacZ model target gene consisting of lacZ 5' "exon" - CFTR mini-intron 9 - CFTR exon 10 (ΔF508) - CFTR mini-intron 10 followed by lacZ 3' "exon" was created, hi this target transcript, a 124 bp central portion ofthe β-galactosidase ORF was substituted by exon 10 (ΔF508) of CFTR, thus it produces non-functional protein. A PTM consisting ofthe missing 124 bp lacZ "mini-exon" and a 5' and 3' trαns- splicing domain containing binding domains (BDs) complementary to the target introns and exons was created. Transfection of HEK 293 T cells with either target alone or PTM alone showed no detectable levels of β-gal activity. In contrast, 293T cells transfected with target plus PTM produced substantial levels of β-gal activity indicating the restoration of protein function. The accuracy of trans-splicing between the target and PTM was confirmed by sequencing the appropriate RT-PCR product, which revealed the predicted internal exon substitution. The feasibility of this approach in a disease model was tested by replacing the CFTR ΔF508 exon 10 with normal exon 10 containing F508 in cystic fibrosis. These results demonstrate that a trans-splicing technology can be easily adapted to correct many ofthe genetic defects whether they are associated with the 5' exon or 3' exon or any internal exon ofthe gene.

Figure 18 is a schematic of a model lacZ target consisting of lacZ 5' exon - CFTR mini-intron 9 - CFTR exon 10 (delta 508) - CFTR min-intron 10 followed by the lacZ 3' exon. hi this target, a 124 bp central portion ofthe lacZ gene is substituted with CFTR exon 10 which has a mutation at position 508 (delta 508). The pre-mRNA target undergoes normal cts-splicing to produce an mRNA consisting of lacZ 5* exon - CFTR exon 10 (delta 508) followed by the lacZ 3' exon. Because of the disruption in β-galactosidase ORF it produces truncated proteins which are nonfunctional.

To restore β-gal function by double-trαns-splicing, three PTMs were created consisting ofthe missing 124 bp lacZ "mini-exon" and a 5' and 3' trans- splicing domain containing binding domains complementary to the target introns and exons as shown in Figure 19. These PTMs have an 120 bp 3' binding domain

(complementary to intron 9) from PTM24 (see below) used in 3' exon replacement, spacer sequence, yeast branch point, polypyrimidine tract, 3' acceptor AG dinucleotide, lacZ "mini-exon", 5' splice site, spacer sequence followed by the 5' binding domain. These PTMs differ only in their 5' binding domain sequences. DSPTM5 has a 27 bp BD which is complementary to intron 10 and blocks just the 5' splice site ofthe target. DSPTM6 has 120 bp 5' BD and covers both 5' and 3' splice sites ofthe target, while, DSPTM7 has 260 bp BD which masks both the splice sites (5' and 3') and also covers the entire exon ofthe target.

A schematic representation of a double-trans-splicing reaction showing the binding of DSPTM7 with DSCFT1.6 target pre-mRNA is shown in Figure 20. 3' BD: 120 bp binding domain complementary to mini-intiOn 9; 5' BD (260 bp); second binding domain complementary to mini-intron 10 and exon 10. ss: splice sites; BP: branch point, and PPT: polypyrimidine tract.

The important structural elements of DSPTM7 (Figure 21) are as follows:

.1 , 3' BD (120 BP): GATTCACTTGCTCCAATTATCATCCTAAGCAGAAGTGTATATTCTTA TTTGTAAAGATTCTATTAACTCATTTGATTCAAAATATTTAAAATACTTCCT GTTTCATACTCTGCTATGCAC f2. Spacer sequences .24 bp : AACATTATTATAACGTTGCTCGAA

(3) Branch point, pyrimidine tract and acceptor splice site:

3' ss

BP Kpn l PPT EcoRV 1 lacZ mini-exon TACTAACTGGTACCTCTTCTTTTTTTTTTGATATCCTGCAG |GGCGGC[

(4) 5' donor site and 2^nd spacer sequence: 5' ss lacZ mini-exon I

|TGAACG| GTAAGT

GTTATCACCGATATGTGTCTAACCTGATTCGGGCCTTC

GATACGCTAAGATCCACCGG (5) 5' BD (260 BP :

TCAAAAAGTTTTCACATAATTTCTTACCTCTTCT TGAATTCATGCTTTGATGACGCTTCTGTATCTATATTC ATCATTGGAAACACCAATGATTTTTCTTTAATGGTGCC TGGCATAATCCTGGAAAACTGATAACACAATGAAATT CTTCCACTGTGCTTAAAAAAACCCTCTTGAATTCTCCA

TTTCTCCCATAATCATCATTACAACTGAACTCTGGAAA TAAAACCCATCATTATTAACTCATTATCAAATCACGC

To determine whether the restoration of β-gal function is RNA trans- splicing mediated, the mutants are depicted in Figure 22. DSPTM8 is a 3' splice mutant in which the 3' splice elements such as BP, polypyrimidine tract and the 3' acceptor AG dinucleotides were deleted and replaced with random sequences. This PTM still has 3' and 5' binding domains and the functional 5' splice site. PTM29 lacks the 2^nd binding domain + 5' ss but still has the 3' binding domain 3' splice site, while PTM30 lacks the 1^st binding domain + 3' splice site but has the functional 5' splice site and 2^nd binding domain.

To examine the double-trans-splicing mediated restoration of β-gal function, 293T cells were either transfected with 2 μg of target or PTM alone or co-transfected with 2 μg of target + 1.5 μg of PTM using Lipofectamine Plus reagent. 48 hrs. after transfection, total RNA was isolated and analyzed by RT-PCR using Kl- 1F and Lac-6R primers. These primers amplify both cis- and trans-spliced products in a single reaction which were identified based on the size. The cz^'s-spliced product is 295 bp in size while the trans-spliced product is 230 bp in size. To confirm that trans-splicing between DSPTM7 and DSCFT1.6 pre-mRNA is precise, RT-PCR amplified products were excised, re-amplified using K1-2F and Lac-6R primers and sequenced directly using K1-2F or Lac-6R primers. As shown in Figure 23 trαns- splicing occurred exactly at the predicted splice sites, confirming the precise internal exon substitution by two trαns-splicing events. The repair of defective lacZ pre-mRNA by double trαns-splicing events and subsequent production of full-length β-gal protein was investigated in co- transfection assays. 293T cells were co-transfected with DSCFT1.6 target and DSPTM7 expression plasmids, as well as with DSCFT1.6 target or DSPTM7 alone as controls. Western blot analysis of total cell lysates using polyclonal anti-β- galactosidase antiserum specifically recognized a ~ 120 kDa protein only in cells co- transfected with DSCFT1.6 target + DSPTM7 plasmids (Fig. 24, lanes 3 and 4) but not in cells transfected with either DSCFT1.6 target (Lane 1) or DSPTM7 plasmid alone (Lane 2). Similarly, no full-length protein was detected in cells co-transfected with DSCFT1.6 target + 3' splice mutant (Lane 5 and 6) or PTM29 or 30 in which either 3' trans-splicing domain or 5' trα?.s-splicing domains has been deleted (Lane 7). In addition, the 120 Da protein band co-migrated with the full-length functional β- gal produced using lacZ-Tl plasmid (positive control, data not shown). These results not only confirmed the production of full-length protein by double-trans-splicing between the target and PTM but also demonstrated that both the 3' splice site and 5' splice sites are essential for this process. To determine whether the full-length protein produced by double- trαns-splicing between the target pre-mRNA and DSPTM7 RNA is functionally active, 293T cells were co-transfected with DSCFT 1.6 targeted + one ofthe double splicing PTMs 5, 6 or 7 expression plasmids, or transfected with DSCFT1.6 target or DSPTM7 alone. Total cell extracts were prepared and assayed for β-gal activity using ONPG assay (Invitrogen). β-gal activity in extracts prepared from cells transfected with either DSCFT1.6 target or DSPTM7 alone was almost identical to the background levels detected in mock transfection (Fig. 25). hi contrast, 293T cells co- transfected with DSCFT1.6 target and DSPTM7 produced - 21 fold higher levels of β-gal activity over the background (Fig. 25). These results confirmed the accurate double-trαns-splicing between the target pre-mRNA and PTM RNA and production ofthe full-length functional protein.

To confirm that restoration of β-gal activity by double-trαns-splicing reaction is absolutely depended on the presence of both 3' and 5' sphce sites ofthe PTM, we constructed several mutants: (a) DSPTM8, is identical to DSPTM7 except the functional 3' spice elements (branch point, polypyrimidine tract and the 3' acceptor AG dinucleotides) were deleted and substituted with random sequences (see Fig. 22 for details); (b) PTM29 lacks 5' splice site as well as the 5' binding domain but has the 3' binding domain and 3' splice site, and (c) PTM30 lacks 3' binding domain and 3' splice site but has the 5' splice site and 5' binding domain, β-gal activity in extracts prepared from cells transfected with either DSCFT1.6 target or DSPTM7 alone was almost identical to the background levels detected in mock transfection (Fig. 26). Similarly, no significant increase in β-gal activity was detected in cells transfected with either DSPTM8 alone (3' splice site mutant) or co-transfection of DSCFT1.6 target + one ofthe above mutant PTMs. On the other hand, cells co-transfected with DSCFT1.6 target and DSPTM7 with functional 3' and 5' splice sites produced substantial levels of β-gal activity over the background (Fig. 26). These results confirmed the requirement of both splice sites in the double-splicing PTM and also eliminated the possibility that restoration of β-gal activity was due to complementation between the truncated proteins (Fig. 26). Different concentrations ofthe target and PTM were co-transfected and analyzed for β-gal activity restoration. As expected, 293T cells co-transfected with DSCFTl.6 target + DSPTM7 showed substantial levels of β-gal activity (~ 30 fold) over the controls. Increasing the concentrations ofthe PTM by 2 and 3 fold did increase the level of β-gal activity, but not significantly (Fig. 27). These results further confirmed the double-trans-splicing mediated restoration of β-gal enzyme function.

The specificity of double-trans-splicing reaction was examined by constructing a non-specific target (DSHCGT1.1) which is similar to that of specific target (DSCFTl .6) but has βHCG intron 1 - βHCG exon 2 and βHCG intron 2 instead of CFTR mini-intron 9 - CFTR exon 10 (delta 508) and CFTR mini-intron 10 (Fig. 28). RT-PCR analysis ofthe total RNA isolated from cells transfected with either DSHCGT1.1 (non-specific target) alone or in combination DSPTM7 (targeted to DSCFTl.6 target) failed to produce the expected 314 bp double-trαns-spliced product. On the other hand, RT-PCR analysis of the total RNA prepared from cells co- transfected with specific target + PTM produced the expected 314 pb product. This was further confirmed by β-gal activity assay ofthe total cellular extract. The level β- gal activity detected in cells transfected with non-specific target alone or in combination with DSPTM7 targeted to DSCFTl. target was almost identical to the background level. In contrast substantial levels of β-gal activity was detected in cells co-transfected with specific target (DSCFTl .6) + DSPTM7 (Fig. 27). These results confirmed that the double-trans-splicing is highly specific.

The repair model in Fig. 30 shows a portion of a target CFTR pre- mRNA consisting of exons 1-9, mini-intron 9, exon 10 containing the delta 508 mutation, mini-intron 10 and exons 11-24 (Fig. 30). The PTM shown in the figure consists of exon 10 coding sequences (containing codon 508) and two trαns-splicing domains each with its own splicing elements (acceptor and donor sites, branchpoint and pyrimidine tract) and a binding domain complementary to intron 9 splice site, part of exon 10 (5' and 3' ends) and intron 10 5' splice site (Fig. 31 (DS-CF1)). Exon 10 of the PTM also has modified codon usage throughout to reduce antisense effects between exon 10 ofthe PTM and it's own binding domains and for PTMs that have binding domains which are complementary to exon sequences (Fig. 1). A double- trans-splicing event between the PTM and target should produce a repaired full- length mRNA.

Fig. 32 shows the sequence of a single PCR product showing target exon 9 correctly spliced to PTM 20 exon 10 (with modified codons) (upper panel), codon 508 in exon 10 ofthe PTM (middle panel) and PTM exόn 10 correctly spliced to target exon 11 (lower panel). The sequence of a repaired target was generated by RT-PCR followed by PCR.

10. EXAMPLE: Ei NS-SPLIClNG REPAIR OF THE CYSTIC FIBROSIS GENE USING A PTM

THAT CAN PERFORM 5' EXON REPLACEMENT

The key advantage of using 5' exon replacement for gene repair are

(a) it permits replacement ofthe 5' portion of a gene

(b) the construct requires less sequence and space than a full-length gene construct,

(c) PTMs can be produced that lack a polyA signal which should prevent PTM translation, and (d) the 5' end can be modified to increase translation.

10.1 MATERIALS AND METHODS

lo.i.i PLASMΓD CONSTRUCTION The CFTR coding sequences (exons 1-10) for PTM30 were generated by PCR using a partial cDNA plasmid template (61160; American Type Culture Collection, Manassas, VA). The trans-splicing domain (TSD) [including the binding domain, spacer sequence, polypyrimidine tract (PPT), branchpoint (BP) and 3' splice site] was generated from a PCR product (using an existing plasmid template) and by annealing oligonucleotides. The different fragments (the TSD and coding sequences) were then cloned into ρcDNA3.1(-) using appropriate restriction sites. Oligodeoxynucleotide primers were procured from Sigma Genosys (The Woodlands, TX). All PCR products were generated with either RED T g (Sigma, St. Louis, MO), or cloned Pfu (Stratagene, La Jolla, CA) DNA Polymerase. PCR primers for amplification contained restriction sites for directed cloning. PCR products were digested with the appropriate restriction enzymes and cloned into the mammalian expression plasmid pc3.1DNA(-) (Invitrogen, Carlsbad, CA).

10.2 CELL CULTURE AND TRANSFECTIONS Constructs were cotransfected in human embryonic kidney (HEK)

293T or 293 cells (1.25 x 10⁶ cells per 60 mm poly-d-lysine coated dish) using LipofectaminePlus (Life Technologies, Gaithersburg, MD) and the cells were harvested 48 h after the start of transfection. Total RNA was isolated as described in the manufacturers instructions (Epicenter Technologies, Inc.). HEK 293T cells were grown in Dulbecco's Modified Eagle's Medium (Life Technologies) supplemented with 10% v/v fetal bovine serum (Hyclone, Inc., Logan, UT). All cells were kept in a humidified incubator at 37 °C and 5% CO₂.

10.1.3 REVERSE TRANSCRIPTION-POLYMERASE

CHAIN REACTION (TR-PCR) RT-PCR was performed using an EZ-RT-PCR kit (Perkin-Elmer,

Foster, CA). Each reaction contained 0.03 to 1.0 μg of total RNA and 80 ng of a 5' and 3' specific primer in a 40 μl reaction volume. RT-PCR products were electrophoresed on 2% Seaken agarose gels. The PTM- and target-specific oligonucleotides used to generate trαns-spliced products are 5'-CGCTGGAAAAACGAGCTTGTTG-3' (primer CF93) and

5'-ACTCAGTGTGATTCCACCTTCTC-3' (primer CF111), respectively. The PTM- and target-specific oligonucleotides used to generate czs-spliced products were CF1 and CF93. The sequence of oligonucleotide CF1 is 5'-GACCTCTGCAGACTTCACTTCTAATGATGATTATGG-3'. The repair model in Fig. 33 shows a portion of a target CFTR pre- mRNA consisting of exons 1-9, mini-intron 9, exon 10 containing the delta 508 mutation, mini-intron 10 and exons 11-24 (Fig. 33). The PTM shown in the figure consists of exon 1-10 coding sequences (containing codon 508) and a trαns-splicing domain with its own splicing elements (donor site, branchpoint and pyrimidine tract) and a binding domain. Several PTMs have been constructed with different binding domains. Three examples are shown in Figure 34. In Fig. 34A the binding domain is complementary to the splice site of intron 9 and part of exon 10 (3' end; CF-PTM 11). In Fig. 34B the PTM has an extended binding domain which also covers the 5' end of exon 10 and the 3' splice site of intron 9 (CF-PTM 20). In the last example (Fig. 34C) the binding domain is the same as that shown in panel B except the binding domain extends the full-length of exon 10 (CF-PTM 30). In the latter case the PTM exon 10 has modified codon usage to reduce antisense effects with it's own binding domain (Fig. 34). Further examples of binding domains are shown in Figure 35.

Figure 36 shows the sequence of cis- and trans-spliced products. The top panel of Fig. 36 A shows target exon 10 with it's three missing nucleotides (CTT), whilst the lower panel shows exon 10 and 11 ofthe target coπectly spliced together. Figure 36B is a partial sequence of a single PCR product showing the modified codons in exon 10 of the PTM (upper panel), codon 508 in exon 10 ofthe PTM (middle panel), and PTM exon 10 correctly spliced to target exon 11 (lower panel), indicating that trαns-splicing is accurate. The sequence ofthe repaired target was generated by RT-PCR followed by PCR.

11. EXAMPLE: PTMs WITH A LONG BINDING DOMAIN, WHICH MAY BE DISCONTINUOUS, HAVE INCREASED ER NS-SPLICING EFFICIENCY AND SPECIFICITY

11.1. MATERIALS AND METHODS

11.1.1. CELL CULTURE

Human embryonic kidney cells (293 or 293T) were from the University of North Carolina tissue culture facility at Chapel Hill (Chapel Hill, NC). , Cells were maintained at 37 °C in a humidified incubator with 5% CO in Dulbecco's modified Eagle's medium (Life Technologies, Bethesda, MD) supplemented with 10% v/v fetal bovine serum (Hyclone, Logan, UT). Cells were passaged every 2-3 days using 0.5% trypsin and re-plated at the desired density. Stable cells, expressing an endogenous mutant lacZ pre-mRNA (lacZCF9) were maintained in the presence of 0.5 mg/ml G418 (Calbiochem, San Diego, CA). 11.1.2. RECOMBINANT PLASMIDS

Targets: ρc3.11acZCF9, ρc3.11acZCF9m, and ρc3.1 lacZHCGlm. pc3.11acZCF9 encodes for a normal lacZ pre-mRNA was constructed using lacZ coding sequences nucleotides 1-1788 as 5' exon, CFTR mini-intron 9 followed by lacZ coding sequences nucleotides 1789-3174 as 3' exon. This is similar to pc3.11acZ-T2 construct but without stop codons in the lacZ 3' exon and has CFTR mini-intron 9 instead of βHCG6 intron 1 (Fig. 37A). CFTR mini-intron 9 was PCR amplified using plasmid T5 as template and primers CFIN-9F (5'- CTAGGATCCCGTTCTTTTGTTCTTCACT ATTAA) and CFLN-9R (5'- CTAGGGTTACCGAAGTAAAACCATACTTATTAG, restriction sites underlined), digested with BamH I and BstE II and cloned in place of BHCG6 intron 1 of pc3.11acZ-T2 plasmid. pc3.11acZCF9m expresses a defective lacZ pre-mRNA and is identical to pc3.11acZCF9 but contains two in-frame non-sense codons in the 3' exon (Fig. 37A). pc3.1 lacZHCGlm is a chimeric target, which includes the lacZ 5' exon followed by intron 1 and exon 2 of βHCG6. This is similar to pc3. llacZCF9m except that it contains exon 2 of βHCG6 in place of mutant lacZ 3' exon. βHCG6 exon 2 was PCR amplified using βHCG6 plasmid (accession # X00266) as template DNA and primers HCGEx-2F (5'- GCATGGTTACCCTGCAGGGGCTGCTGCTGTTGCTG) and HCGEx-2R (5'- CTGAAAGCTTGTTAACCAGCTCACCATGGTGGGGCAG, restriction sites underlined) digested with BstE II and Hind HI and cloned in place ofthe lacZ 3' exon of pc3.11acZCF9m. Plasmid pcDNA3.1/HisB//αcZ (Invitrogen, Carlsbad, CA) was used as DNA template to produce 5' and 3' lacZ exons. The lacZ 5' exon is 1788 bp long, has an ATG initiation codon, lacZ exon (without stop codons) is 1385 bp long and has a transcription termination signal at the end ofthe 3' exon. CFTR mini-intron 9 and βHCG6 intron 1 are 548 bp and 352 bp in size, respectively, and both have 5' and 3' splice signals. Exon 2 of βHCG6 is 162 bp long and has a transcription termination signal at the end ofthe exon.

Pre-trans-splicing Molecules (PTMs): PTM-CF14 is an identical version of pcPTMl with minor modifications in the trαns-sphcing domain (Fig. 37B). PTM-CF14 is a linear version and contains a 23 bp antisense binding domain (BD) (5'-ACCCATCATTATTAGGTCATTAT) complementary to CFTR mini-intron 9, 18 bp spacer, a canonical branch point sequence (UACUAAC; BP) and an extended polypyrimidine tract (PPT) followed by normal lacZ 3' exon. PTM-CF22, PTM- CF24, PTM-CF26 and PTM-CF27 are identical to PTM-CF14 except they differ in length ofthe BD (Fig. 37B). sPTM-CF18 has a 32 bp BD, sPTM-CF22 and sPTM- CF24 contain the same BD as PTM-CF22 and PTM-CF24, respectively. In these PTMs, the binding domains were modified to create intra-molecular stem-loop structure ("safety") to mask the 3' splice-site ofthe PTM. Different binding domains were produced by PCR amplification using specific primers (with unique Nhe I and Sac II sites) and a plasmid containing CFTR mini-intron 9 as template. PCR products were digested with Nhe I and Sac II and cloned into a PTM plasmid consisting of spacer sequences, 3' splice elements (BP, PPT and acceptor AG dinucleotide) followed by a normal lacZ 3' exon.

11.1.3. TRANSFECTION OF PLASMID DNAs P TO 293T CELLS The day before transfection, 1 x 10⁶293T cells were plated on 60 mm plates coated with Poly-D-lysine (Sigma, St. Louis, MO) to enhance the adherence of cells and grown for 24 hr at 37°C. Cells were transfected with expression plasmids using LipofectaminePlus reagent according to standard protocols (Life Technologies, Bethesda, MD). In a typical co-transfection, 2 μg of pc3.11acZCF9m target and 1.5 μg of PTM expression plasmids were transfected into cells and for controls (target and PTM alone transfections) total DNA concentration was normalized to 3.5 μg with pcDNA3.1 vector.

Forty-eight hours after transfection the plates were rinsed with PBS, cells harvested and total RNA or DNA was isolated using MasterPure RNA DNA purification kit (Epicenter Technologies, Madison, WI). Contaminating DNA in the RNA preparation was removed by treating with DNase I, while, contaminating RNA in the DNA preparation was removed by digesting with RNase A at 37°C for 30-45 min. 11.1.4. REVERSE TRANSCRLPTION-POLYMERASE

CHAIN REACTION (RT-PCR)

RT-PCR was performed as suggested by manufacturer using an EZ rTth RNA PCR kit (Perkins-Elmer, Foster City, CA). A typical reaction (50 μl) contained 25-500 ng of total RNA, 100 ng of 5' target specific primer (common to cis- and trαns-spliced products) (Lac-9F, 5'-GATCAAATCTGTCGATCCTTCC) and 100 ng of 3' primer (Lac-3R, 5'-CTGATCCACCCAGTCCCATTA, target specific primer for c/s-splicing, and Lac-5R, 5'-GACTGATCCACCCAGTCCCAGA, PTM specific primer for trαns-splicing), IX reverse transcription buffer (100 mM Tris-HCI, pH 8.3, 900 mM KCL with 1 mM MnCl₂), 200 μM dNTPs and 10 units of rTth DNA polymerase. RT reactions were performed at 60°C for 45 min. followed by 30 sec pre-heating at 94°C and 25-35 cycles of PCR amplification at 94°C for 18 sec, annealing and extension at 60°C for 1 min followed by a final extension at 70°C for 7 min. The reaction products were analyzed by agarose gel electrophoresis.

11.1.5. PROTEIN PREPARATION AND β-GAL ASSAY

Total cellular protein from cells transfected with expression plasmids was isolated by freeze thaw method and assayed for β-galactosidase activity using a β-gal assay kit (Invitrogen, Carlsbad, CA). Protein concentration was measured by the dye-binding assay using Bio-Rad protein assay reagents (BIO-RAD, Hercules, CA).

11.1.6. WESTERN BLOT

About 5-25 μg of total protein was electrophoresed on a 7.5% SDS- PAGE gel and electroblotted onto PVDF-P membrane (Millipore). After blocking for 1 hr at room temperature (blocking buffer: 5% dry milk and 0.1% Tween-20 in IX PBS), the blot was incubated with a 1 :2500 dilution of polyclonal rabbit anti-β- galactosidase antibody for 1 hr at room temperature (Research Diagnostics Inc. NJ), washed 3x with blocking buffer and then incubated with a 1 :5000 diluted anti-rabbit HRP conjugated secondary antibody. After incubating at room temperature for 1 hr, it was washed 3x in blocking buffer and developed using ECLPlus Western blotting reagents (Amersham Pharmacia Biotech, Piscataway, NJ).

11.1.7. IN SITU β-GAL STAINING

Cells were monitored for the expression of functional β-galactosidase using a β-gal staining kit (Invitrogen, Carlsbad, CA). The percentage of β-gal positive cells were determined by counting stained vs. unstained cells in 5-10 randomly selected fields.

11.1.8. SELECTION OF NEOMYCIN RESISTANT CLONES EXPRESSING AN ENDOGENOUS DEFECTIVE lacZ PRE-mRNA TARGET

On day 1, 1 x 10⁶293 cells were plated on 60 mm plates and grown for 24 hr at 37°C. On day 2, the cells were transfected with 2 μg of pc3.11acZCF9m using LipofectaminePlus transfection reagent as described above. 48 hr post- transfection, cells were split (1 :20 ratio) and grown in media containing 0.5 mg/ml G418. At the end of 2 weeks, neomycin resistant colonies were selected, pooled, expanded and maintained constantly in the presence of G418.

11.2. RESULTS

A model system was developed that permits facile and versatile analysis of spliceosome mediated RNA trαns-splicing in cells. The bacterial lacZ gene was split with a truncated intron 9 from the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene (Figure 37 A). This split lacZ gene, when introduced into human 293T cells, directed the synthesis of a lacZ pre-mRNA that could splice properly. The open reading frame ofthe lacZ gene was mutated by insertion of two in-frame nonsense codons near the 5' end ofthe second exon (Figure 37A). This lacZ gene is referred to as lacZCF9m. hi 293T cells, lacZCF9m directs the synthesis of lacZCF9m pre-mRNA, which encodes a truncated β-galactosidase (β- gal) protein that does not have enzymatic activity. Cells bearing the lacZCF9m gene are a model system for genetic disorders caused by loss of function mutations. Pre-trαns-splicing molecules (PTMs) were designed to trans-splice with lacZCF9m pre-mRNA and repair the mutation caused by the two nonsense codons. PTMs were constructed with binding domains spanning 23, 91 and 153 nucleotides (nt), which we named PTM-CF14, PTM-CF22 and PTM-CF24 (Figure 37B). The PTM-CF24 binding domain does not bind 153 contiguous nt in the targeted CFTR gene intron 9, but rather creates a loop of 47 nt in the target in between two regions of complementary of 27 and 126 nt (Figure 37B). These PTMs were predicted to repair the deficiency created by lacZCF9m (Figure 37C).

Semi-quantitative RT-PCR analysis was used to tests the efficiency of trαns-splicing mediated by PTMs with long target binding domains. Repair of lacZCF9m transcripts by trαns-splicing was tested in two different ways: co- transfection of PTM and target (lacZCF9m) plasmids or transfection of cells that had been modified to express the target as an endogenous pre-mRNA. Co-transfecting plasmids encoding PTMs with the lacZCF9m plasmid provided a facile method for screening the former for efficiency. PTM-CF22 and PTM-CF24 were approximately 3-fold and 10-fold more efficient than PTM-CF14 in a semi-quantitative RT-PCR assay suggesting a significant improvement in mRNA repair (Figure 38). Sequencing ofthe RT-PCR products showed that trαns-splicing was accurate, resulting in proper ligation ofthe exons from the target and the PTM. Moreover, mutation of key cis- acting elements in the 3' splice site ofthe PTMs resulted in an abrogation of trαns- splicing. In these and all other assays described herein controls were carried out to rule out recombination at the DNA level. Thus, repair o the lacZCF9m transcripts was a result of targeted RNA trans-splicing.

Transfection of PTM-CF14, -CF22 or -CF24 into 293 cells bearing an endogenous lacZCF9m gene confirmed that the longer target binding domains provided the PTMs with higher efficiency (Figure 38B). It should be noted that similar levels of RT-PCR trans-splicing specific product were obtained after 30 PCR cycles and 35 cycles for PTM-CF24 and PTM-CF14, respectively. The data therefore suggests that PTMs with long binding domains repaired lacZCF9m transcripts at least an order of magnitude better than previously described PTMs. More than one in ten transcripts of lacZCF9m can be repaired by trans- splicing. Quantitative, real-time PCR was used to measure the f action of lacZCF9m transcripts repaired by PTMs with long binding domains. The co-transfection assay described above was used in these experiments. PTM-CF14, which contains a binding domain of 23 nt, was shown to repair between 1.2 and 1.6% of lacZCF9m RNAs in 293T cells and 2.1% of lacZCF9m RNAs in the H1299 human lung cancer cells. PTM-CF24, which has a 153 not long binding domain, was significantly more efficient, correcting between 12.1 and 15.2% of lacZCF9m RNAs in 293T cells and 19.7% in H1299 cells. This in effect resulted in a measurable reduction in the levels of lacZCF9m mRNA. These data also confirmed the remarkable capability of this RT-PCR assay to distinguish between the products of czs-splicing, the lacZCF9m and mRNA, and the products of trαns-splicing, repaired lacZCF9m mRNA. This is the first true quantification ofthe efficacy of trans-splicing mediated mRNA repair at the RNA level. These data confirm the suggestions ofthe semi-quantitative RT-PCR analysis shown above. Similar experiments were carried out using 293 cells that express an endogenous lacZCF9m pre-mRNA target. Consistent with the data shown above, PTM-CF24 was ten times more efficient than PTM-CF14, with the former correcting between 1.3 and 4.1% of endogenous lacZCF9m transcripts. These data confirmed that increasing the length ofthe PTMs provided a remarkable enhancement in trans-splicing efficiency.

Erans-splicing mediated mRNA repair results in the synthesis of active β-galactosidase. At the cellular level, the ultimate criterion for the success of mRNA repair is the production of an active protein. Using a western assay it was determined that full-length β-gal was produced as a result of trans-splicing . Full-length β-gal was not observed following transfection of 293T cells with plasmids encoding lacZCF9m or PTM-CF24. Co-transfection of both plasmids, however, resulted in robust production of full-length β-gal protein, which was readily detectable using anti-β-gal antiserum (Figure 39). This result complements enzymatic activity data suggests that the latter was not due to a complementation by truncated β-gal proteins. The Western blot analysis revealed that full-length β-gal protein was made in 293T cells by trans-splicing and furthermore confirmed that the PTMs with long binding domains were efficiently spliced.

Appropriate repair of β-gal mRNA and synthesis of full-length β-gal protein should lead to the production of active enzyme. Indeed, 293T cells co- transfected with lacZCF9m and PTM-CF24 were shown to have β-gal activity measured either in situ (Figure 40 A) or in extracts (Figure 40B). This activity was shown to depend on the trαns-sphcing between the target pre-mRNA and the PTM. The quantitative in solution assay further confirmed the data presented above: PTM- CF22 and PTM-CF24 were 2.9 and 9.3 fold more efficient respectively than PTM- CF14. Most impressive, however, were results using 293 cells that harbor lacZCF9m as a stable endogenous gene. When these cells were transfected with PTM-CF14 the levels of β-gal activity obtained were barely above background. Transfection with PTM-CF24, however, resulted in a considerable level of β-gal activity (Figure 40C). This was paralleled by the appearance of full-length β-gal protein. These data demonstrate a sizeable increase in the efficiency of trαns-splicing to repair a mutated pre-mRNA. In fact all prior reports of repair of endogenous RNA in mammalian cells by either group I ribozymes or trαns-splicing have been only documented using RT- PCR, an indication ofthe low level of repair.

PTMs with very long binding domains are highly specific. It was shown that a secondary stracture within the binding domain could enhance specificity of PTMs in HeLa nuclear extracts. In order to ascertain the specificity ofthe trans- splicing reactions in vivo a second target gene was prepared, which could serve as reporter of non-specific reactions. This gene, which is referred to as lacZHCGlm, shares the first exon with lacZCF9m. The intron in lacZHCGlm is intron 1 ofthe β- subunit ofthe human chorionic gonadotiopin gene 6 (βhCG6) and the second exon is exon 2 ofthe same gene. lacZHCGlm drives the synthesis of a pre-mRNA that is spliced coπectly to yield a chimeric mRNA that does not encode a full-length β-gal (see below). PTM-CF14, -CF22 and -CF24 are not targeted to lacZHCGlm pre- mRNA since there is no complementarity between the binding domains in these PTMs and the target gene. Any trans-splicing between these PTMs and lacZHCGlm pre-mRNA is therefore non-specific (Figure 41 A). 293T cells were transfected with PTM-CF14, -CF22 or -CF24 and the level of non-specific trans-splicing was determined by RT-PCR and by in solution β-gal assays. Semi-quantitative RT-PCR suggested that PTM-CF24 was significantly less likely than PTM-CF14 to trans-splice with lacZHCGlm pre-mRNA. Measurement of β-gal activity confirmed this; cells co-transfected with lacZHCGlm and PTM-CF24 produced 3.1 fold less β-gal than those co-transfected with lacZHCGlm and PTM-CF14 (Figure 41C). Based on these data it was estimated that PTM-CF24 is 50 times more likely to trans-splice to its target than to a non-specific target. A "safety" version of PTM-CF24, sPTM-CF24, did not confer further specificity (Figure 41C). Nonetheless, for PTMs with shorter binding domains a "safety" stem involving the binding domain was seen to improve specificity in vivo (Figure 41 C). It was concluded from these data that the longer binding domains resulted in PTMs that were not only more efficient but also more specific.

The observation that long binding domains increased the specificity of PTMs suggested that very long binding domains (>200 nt) could further enhance discrimination. Plasmids encoding PTM-CF26 and -CF27, which have binding domains that span 200 nt and 411 nt respectively, were constructed and co-transfected with lacZHCGlm plasmid. Non-specific trans-splicing of these two PTMs was barely detectable with RT-PCR (Figure 41B). As measured by the β-gal assay PTM- CF26 and -CF27 had minimal non-specific trans-splicing activity (Figure 41C). In a specific trans-splicing reaction with lacZCF9m as measured by the solution β-gal assay PTM-CF26 was as active as PTM-CF14 (Figure 41B). It was estimated that PTM-CF26 is 80 times more likely to trans-splice to the specific target (lacZCF9m) than to a non-specific target (lacZHCGlm). Therefore, inclusion of very long binding domains confers to these PTMs very high specificity.

12. EXAMPLE: CORRECTION OF THE FACTOR VIII GENE USING 3' EXON REPLACEMENT

Hemophilia is a bleeding disorder caused by a deficiency in one ofthe blood clotting factors. Hemophilia A, which accounts for about 80 percent of all cases is a deficiency in clotting factor VIII. The following section describes the successful repair ofthe clotting factor VIII gene using spliceosome mediated trans- splicing and demonstrates the feasibility of repairing the factor VIII using gene therapy.

The coding region for mouse factor VIII PTM (exons 16-24) was PCR amplfied from a cDNA plasmid template using primers that included unique restriction sites for directed cloning. All PCR products were generated with cloned Pfu DNA Polymerase (Stratagene, La Jolla, CA). The coding sequence was cloned into pc3.1DNA(-) using EcoRV and Pmel restriction sites. The binding domain (BD) was created by PCR using genomic DNA as a template. Primers included unique restriction sites for directed cloning. The PCR product was cloned into an existing PTM plasmid (PTM-CF24, pc3.1DNA) using Nhel and SacII restriction sites. This plasmid already contained the remaining elements ofthe TSD including a spacer sequence, polypyrimidine tract (PPT), branchpoint (BP) and 3' acceptor site. The whole ofthe TSD was then subcloned into the vector (described above) containing the factor VIII PTM coding sequences. Finally, bovine growth honnone 3' untranslated sequences from a separate plasmid clone were subcloned into the above PTM using Pmel and BamHI restriction sites.

The whole construct was sequenced and then analyzed by RT-PCR for possible cryptic splicing, and then subcloned into the AAV plasmid pDLZ20-M2 using Xhol and BamHI restriction sites (Chao et al, 2000, Gene Therapy 95:1594- 1599; Flotte and Carter, 1998, Methods Enzymol, 292:717-32). For some viral (and non-viral) delivery systems, the size ofthe therapeutic is essential. Viral vectors such as adeno-associated virus are preferred because they are a (i) non-pathogenic virus with a broad host range (ii) it induces a low inflammatory response when compared to adenovirus vectors and (iii) it has the ability to infect both dividing and non-dividing cells. However, the packaging capacity ofthe rAAV is limited to approximately 110% ofthe size ofthe wild type genome, or -4.9 kB, thus, leaving little room for large regulatory elements such as promoters and enhancers. The B-domain deleted human factor VIII is close to the packaging size of AAV , thus, trαns-splicing offers the possibility of delivering a smaller transgene while permitting the addition of regulatory elements. To eliminate cryptic donor sites in the pre-mRNA upstream ofthe Xhol PTM cloning site approximately 170 bp of sequence was eliminated from the original AAV construct that includes part of exon 1 and all ofthe intron 1 sequence (see Fig. 44C). The repair model in Fig. 44D shows a simplified model ofthe mouse factor VIII pre-mRNA target (endogenous gene) consisting of exons 1-14, intron 14, exon 15, intron 16, and exon 16-24 containing a neomycin gene insertion. The PTM shown in the figure consists of exon 16-24 coding sequences and a trans-splicing domain with its own splicing elements (donor site, branchpoint and pyrimidine tract) and a binding domain. Details ofthe binding domain are shown in Fig. 44A and 44B. The binding domain is complementary to the splice site of intron 15 and part of exon 16 (5' end).

The key advantages of using 3' exon replacement for gene repair are (i) the construct requires less sequence and space than a full length gene construct, thereby leaving more space for regulatory elements, (ii) SMaRT repair should only occur in those cells that express the target gene, therefore eliminating any potential problems associated with ectopic expression of repaired RNA.

Factor VUI deficient mice were maintained at the animal facilities at the University of North Carolina at Chapel Hill. For plasmid injections each mouse was sedated and placed under a dissecting microscope and a 1 cm vertical midline abdomen incision was made. Approximately 100 micrograms of PTM plasmid DNA in phosphate buffered saline was injected to liver portal vein. Blood was collected from the retro-orbital plexus at intervals of 1, 2, 3 and 20 days after injection and assayed for factor VLTI activity using the Coatest assay. Factor VIII activity in blood samples collected from mice were assayed using a standard test called the Coatest assay. The assay was performed according to manufacturer's instructions (Chromgenix AB, Milan, Italy). Data indicating repair of factor VUI in factor VIII knock out mice is demonstrated in Figure 46.

Hemophilia A defects in humans are broadly split into several categories that include gross DNA rearrangements, single DNA base substimtions, deletions and insertions. It has been determined that a rearrangement of DNA involving an inversion and translocation of exons 1-22 (together with introns) away from exons 23-26 is responsible for ~40% of all cases of severe hemophilia A. The canine hemophilia A model also has a very similar gross rearrangement. This mutation will be used as the basis for our human and canine factor VUI PTM designs. Methods for building the human factor VIII PTM will be very similar to that described above for the mouse PTM except that different coding regions (exons 23-26) will be amplified from a human cDNA, the binding domain will be amplified from human genomic sequence templates (whole genomic DNA or a genomic clone), and a C-terminal FLAG tag will be engineered in the PTM to be used to detect repaired factor VIJJ protein. The remaining elements ofthe trans-splicing domain including a spacer sequence, polypyrimidine tract (PPT), branchpoint (BP) and 3' acceptor site will be obtained from an existing plasmid. Where necessary changes will be made to the binding domain sequence to eliminate any cryptic splicing within the PTM. The final PTM will be subcloned into the same mouse AAV plasmid vector, pDLZ20-M2 and virus preparation made from this plasmid. The canine factor VIII PTM will be made in an identical fashion but using canine cDNA and genomic plasmid.

13. EXAMPLE: TARGETED TRANS-SP CWG OF PAPJLLOMAVIRAL RNA The vast majority of cervical cancers are associated with oncogenic human papilloma viruses (HPVs) and express viral mRNAs encoding the Ε6 and E7 oncoproteins. As described below, PTMs targeted against the E6 region of HPV-16 and splice the TM exon to the 5' end ofthe E6 ORF using the 5' splice site at the nucleotide 226.

13.1 MATERIALS AND METHODS

The target DNA (pi 059) was used to test PTM efficiency and contains the entire HPV-16 early region (nt 79-4468) cloned behind the SV40 early promoter and origin of replication. Specificity was assessed using the heterologous expression vector lacZCF9m as target (Puttaraju et al. 2001. Mol Ther 4:105-14). PlaSmids were prepared using Quiagen maxi prep kits. Nearly confluent 6 cm plates of 293 cells were transfected with 2 μg target DNA and 2 μg PTM DNA using LipofectAmine 2000 (Life Technologies). At two days post-transfection, cells were washed on the plate with PBS and lysed on the plate using 300 μl lysis buffer. Total cell RNA was prepared using Ambion RNAqueous kit. Transfected DNA was removed from the RNA by LiCl precipitation followed by DNAse I treatment using the Amboin DNA-free™ DNAse treatment and removal reagents.

RNA was converted to cDNA using RT from the High Capacity cDNA Archive Kit (PE Applied Biosystems) as directed by the manufacturer with the following modifications: the amount of random primer was cut in half and 5 μl of a 50 μM stock of oligo(dT16) and 5 μl of a 20 unites/μl stock of RNAse inhibitor were added per 100 μl reaction. RT reactions were diluted to 50 ng/μl and 5 ng/μl (based on original RNA content) for real time Quantitative PCR (QPCR) analysis. Amounts of specific cis and trans spliced mRNAs were quantitated using Real Time Quantitative PCR. These assays are referred to as Real Time QRT-PCR. These reactions were carried out on the Bio-Rad iCycler iQ Real Time PCR instrument using the S YBR Green kit from PE Applied Biosystems essentially as described previously (Puttaraju et al. 2001 Mol Ther 4:105-14.).

Total HPV-16 RNA levels (cis and trans-spliced) were assessed using a common amplicon in E6 exon 1 (HPV-16 nt 152-204; 53 bp). This assay uses the HPV-16 primers oJMD-15 (ACAGAGCTGCAAACAACTAT) and oJMD-16 (TTGCAGTACACATTCTAA). The amount of RT reaction used for each PCR reaction was 5 ng. Trans-splicing from the HPV-16 nt 226 5' sphce site to the PTM lacZ exon was assessed using a 53 bp chimeric amplicon. This assay uses the HPV- 16 senser primer oCCB-348 (GCAAGCAACAGTTACTGCGA; HPV-16 nt 201-220) and the lacZ antisense primer oCCB-322 (ATCCACCCAGTCCCAGA). The amount of RT reaction used for each PCR reaction was 50 ng. Both assays used the same plasmid (p3671) to generate standard curves for quantitation. Trans-splicing from the HPV-16 nt 880 5' splice site to the PTM lacZ exon was assessed using a 50 bp chimeric amplicon. This assay uses the HPV- 16 sense primer oCCB-366

(ATCTACCATGGCTGATCCTG; HPV-16 nt 858-877) and the lacZ antisenser primer oCCB-322. The amount of RT reaction used for each PCR reaction was 50 ng. The plasmid p3672 was used to generate the standard curve for this assay.

Plasmids used as standards for real time QPCR were cloned as follows. An RT reaction from cotransfections of pl059 and HPV-PTMl in 293T cells was used as template for PCR reactions. Primers oCCB-257 (HPV-16 nt 127-147;

ACCCAGAAAGTTACCACAGTT) and oCCB-322 gave a 127 bp band which was TOPO-cloned into pCRII-TOPO (Invitrogen) to give p3671. Sequencing showed that this DNA corresponds to trans-splicing from HPV-16 nt 226 into the 3' splice site of the PTM. Primers oJMD-17 (HPV-16 nt 689-708; GACAAGCAGAACCGGACAGA) and oCCB-322 gave a 219 bp band which was TOPO-cloned into pCRII-TOPO to give p3672. Sequencing showed that this DNA coπesponds to trans-splicing from HPV-16 nt 880 into the 3' splice site ofthe PTM. Plasmids stocks (1 ng/μl) were quantitated using PicoGreen (Molecular Probes) prior to use for standard curves. Quantitation of cis- and trαns-splicing for the cotransfections with

PTMs and the target lacZCF9m were done exactly as described previously (Puttaraju et al. 2001. Mol. Ther. 4:105-14). The amount of RT reaction used for each PCR reaction was 5 ng.

13.2 RESULTS HPV and CF PTMs were contransfected into 293 cells with either the

HPV-16 expression vector pl059 to assess trans-splicing efficiency or with lacZCF9m (containing a CF intron) to assess trαns-splicing specificity. Real Time QRT-PCR assays were done as described above to assess levels of trans-splicing relative to czs-splicing of each target. The results are shown in Table 1. All RNA levels are expressed as fg ofthe DNA standard. The standards p3671 and p3672 are close to the same size so these values can be used to represent relative RNA levels for each assays. HPV-PTMl, 2, 5, and 6 efficiently trans-spliced to the HPV-16 nt 2265' splice site. Up to 70% trans-splicing was seen for the HPV-PTMl. As expected, HPV-PTM5 trans-splicing was abolished by mutations in the branch point and polypyrimidine tracts ofthe PTM. These PTMs showed less than 1% trans-splicing to the nt 880 5' splice site. This data is consistent with the design of these PTMs which have binding domains complementary to the nucleotide 409 and 526 3* splice sites. HPV-PTM-8 and HPV-PTM-9 trans binding domains downstream ofthe nt 880 5' splice site and show efficient trαns-splicing to this 5' splice site (37% for HPV-PTM8 and 22% for HPV-PTM9) and somewhat less efficient trans-splicing to the nt 226 5' splice site. HPV-PTM9 may interfere sterically with binding of splicing factors to the nt 880 5' splice site. The specificity of HPV-PTMl, 2, 5 and 6 was also assessed by their ability to trans-splice to a target pre-mRNA with a CF intron. Specificity ranged from 274 to 606 fold.

MSP Co-transfection 8/2/01 o 293 cells Specificity Assay

© Target: p3514 (LacZCF9m) (all cells have target) o 6 cm plates; LipofectAmine 2000; 2 ug target and 2 ug PTM p3517 for cis splicing standard curve

H U p3519 for trans-splicing standard curve α.

Std curve: p3517 p3519

Primers: 324/323 327/322

Sample. Transfection #/PTM fα cis fq trans %Trans

1 #1A HPV-PTM1 1,200.00 1.44 0.1%

2 #1B HPV-PTM1 1,380.00 3.60 0.3%

3 #2A HPV-PTM2 2,840.00 4.10 0.1%

4 #2B HPV-PTM2 2,090.00 3.17 0.2%

5 #3A HPV-PTM5 1,820.00 1.85 0.1%

6 #3B HPV-PTM5 1,750.00 1.82 0.1%

7 #4A HPV-PTM6 772.00 0.69 0.1%

8 #4B HPV-PTM6 1,720.00 2.05 0.1%

90 9 #5A HPV-PTM8 2,570.00 5.06 0.2%

10 #5B HPV-PTM8 1,800.00 3.46 0.2%

11 #6A HPV-PTM9 2,300.00 2.29 0.1%

12 #6B HPV-PTM9 2,690.00 2.74 0.1%

13 #7A CF14 1,350.00 22.20 1.6%

14 #7B CF14 1,320.00 21.50 1.6%

15#8ACF24 1,520.00 93.90 5.8%

16#8BCF24 1,500.00 72.00 4.6%

17#9ACF27(OKb PCR) 1,410.00 3.83 0.3%

18 #9B CF27 (OK by PCR) 1,370.00 4.53 0.3%

21 #11ApcDNA3.1 1,520.00 0.04 0.0%

22#11BpcDNA3.1 1,370.00 0.07 0.0%

23p3517(10pg) — 0.17

90 IΛ 24p3519(10pg) 0.00 - —

C.

© Note: the identity of the CF PTMs was rechecked by PCR of both the plasmids and the RNA samples (before DNAse treatment) and are OK. o

14. EXAMPLE: DESIGN OF TARGETED PAPILLOMA VIRUS

PTMs

Initial pre-therapeutic RNA molecules ("PTMs") are developed based on the abundance and splicing patterns of HPV mRNA. The transcription map of HPV-16 in benign infections is shown in Figme 48. Cis and trans splicing assays are performed on the initial PTMs and the data obtained from the assays is used to create specific PTMs with optimized efficacy in spliceosome-mediated RNA trans-splicing reactions.

The most effective PTM is one that tr ns-splices an HPV target transcript with a PTM encoding a toxic product which will kill the infected cell. In targeting the most frequently used HPV splice sites, two viable 5' splice site targets and two viable 3' splice site targets can be used. Less frequently used splice sites can also make good targets if the PTM is designed to block the more frequently used site. Choice of target splice sites is further restricted if the intention is to treat cancers, since integration of HPV-16 in many cervical cancers leads to expression of only the E6 and E7 regions in these cancers.

The following target splice sites are used in the development ofthe initial PTMs which leads to the expression of a toxic product: i) 5' splice site targets: - nt 226: This splice site is used in the synthesis of all E6* species.

In most tumors and cell lines, the vast majority of P97 promoter transcripts will be spliced using this 5' splice site.

- nt 880: This splice site is used in the synthesis of all E6US (unspliced) and E6* species except E6*IE_, both splice sites are good targets in both productive infections and cancers; and

ii) 3' splice site targets:

- nt 409: This 3' splice site is used in the splicing of £6*1 species which are generally more abundant than E6*II species. This splice site is used in cancers and productive HPV infection. - nt 3358: This target is used for splicing of most mRNAs, but only if the viral DNA is extrachromosomal. This splice site is not a good target for the treatment of most cancers.

In addition, a double trαns-splicing PTM is developed to replace the internal exons nt 409-880 or nt 526-880 in productively infected tissue and in cancers.

Alternatively, initial PTMs are designed in which trans-splicing produces an mRNA encoding a fusion protein that is part viral and part exogenous peptide encoded by the PTM. The fusion protein will change the function of the viral protein so that it inhibits an essential viral function. The splice sites listed above are targeted to produce three viral fusion proteins:

(i) The E6 N terminus, using the nt 226 5' splice site as the target;

(ii) The E6 C terminus, using the nt 409 (best) or nt 526 3' splice sites as the targets; and

(iii) The E2 C terminus, using the nt 3358 3' splice site as target. This fusion protein is produced in productive infections and cancers containing extrachromosomal viral DNA. The C terminal domain of E2 is the DNA binding and dimerization domain, and can be used to target a fusion protein to the P97 promoter and block transcription. At high concentrations, the E2 viral protein binds just upstream ofthe P97 promoter and inhibits transcription by competing with the transcription factors, SPl and TFIID, for binding. However, these E2 binding sites are weaker than those upstream in the Long Control Region (LCR) and are only saturated at high concentrations ofthe viral E2 protein. At low concentrations of E2, the protein binds to the E2 binding sites in the upstream LCR and activates transcription. Thus, a "repressor" domain can be added to the fusion protein resulting in a block of transcription through binding to any E2 binding site. This fusion protein is also useful to block viral DNA replication, since an E1/E2 complex binds the origin of replication. It has been demonstrated, however, that a complex ofthe E2 DNA binding domain and El does not bind to the origin. Since E2 is a dimer, heterodimerization ofthe E2 fusion protein with full length E2 protein would probably eliminate E2 function in DNA replication. PTM(s) based on their ability to target and trans-splice to the HPV target splice sites depicted in Figure 48 listed above are constructed and screened such that splicing results in the expression of diphtheria toxin sub unit A (DT-A) product, which will kill the infected cells or express a marker gene which can be easily detected. Other peptide or protein toxins may also be encoded. A typical prototype PTM (3' trans-splicing) consists of an antisense target binding domain (25 or more) complementary to HPV sequences, spacer sequence, canonical branchpoint sequence (UACUAAC), an extensive polypyrimidine tract (12-15 U's), AG dinucleotide ofthe 3' splice site followed by the delivered gene. PTMs are also constructed to carry out PTM-mediated trans-splicing with HPV 3' splice sites (Fig. 66B). The trans-splicing domain (TSD) ofthe PTMs are constructed in modular fashion. Unique restriction sites are incorporated between each ofthe PTM elements, facilitating the replacement of individual elements. Schematic diagrams of 3' exon replacement and 5' exon replacement models are shown (Figure 66A-B), respectively. It has previously been demonstrated that both efficiency and specificity of trans-splicing can be modulated substantially by altering several sequences in the TSD, including, the length ofthe binding domain, spacer sequences, strength ofthe PPT etc.

"Linear" PTMs are designed initially to maximize the trans-splicing efficiency, thereby identifying the PTM sequences that provide highest trans-splicing efficiency. Linear PTMs refer to the binding domain in the PTM as single stranded in configuration To achieve a higher degree of targeting specificity, another form of TSD referred to as a "safety stem" can be constructed, h these PTMs, the splice site ofthe PTM is protected from reacting with other pre-mRNA targets by binding to itself in a folded structure. Contact with the specific target promotes unwinding ofthe safety stem exposing and activating the PTM's 3' splice site for spliceosome formation.

To further enhance the trans-splicing specificity, a PTM that requires two trαns-splicing events to produce the expected therapeutic effect is also constructed (Fig. 65). This PTM will have an upstream 3' splice site that will trans- splice into an HPV 5' splice site, producing a singularly trans-spliced product. This product does not contain the required polyadenylation signals and would be inactive due to failure in nucleocytoplasmic transport and translation ofthe mRNA. A second trans-splicing event with a HPV 3' splice site is necessary to provide the PTM with the signals required for polyadenylation (Fig. 65). Polyadenylation is necessary for PTMs with linear binding domains in which both 3' and 5' binding domains are linear, or with 3' safety + 5' linear binding domains, are also designed for inhibition of viral expression. In addition, PTMs are designed as "double safety" PTMs with both 3' and 5' safety splice sites or 3' linear or 5' safety sites.

Testing ofthe PTMs is performed using in vitro splicing assays and cell culture-based assays. HPV-16-containing cell lines are used for testing the ability of PTMs to trans-splice. W12 cells (80263 cells) contain extrachromosomal HPV-16 DNA and express the full HPV-16 early region and can be used to test PTMs targeting. SiHa and CaSki cell lines contain integrated HPV-16 and express only the viral E6/E7/5Ε1 regions. These cell lines are useful because they express viral pre- mRNAs characteristic of those expressed in cervical cancers. However, they may not be useful cell lines for testing aPTM targeting the nt 3358 3' splice site. CaSki cells express considerably higher levels of HPV-16 mRNAs than any ofthe other cell lines tested and therefore may be the best cells for assaying other PTMs.

Cell culture-based cotransfection experiments with a PTM expression vector and an HPV-16 early region expression vector are assayed for expression of the PTM. Several plasmids driving the expression of HPV-16 have been constructed. For example, two plasmids that can be used in co-transfection experiments include ones that express HPV-16 under the direction of either the SV40 early promoter (pl059) or the K14 promoter (p2571; pK14-1203).

Combined isoform-specific (i.e. splice-specific) primers with quantitative real time reverse transcription polymerase chain reaction (QRT/PCR) are used to assay for alternative splicing. This assay is very isoform specific, relatively insensitive to RNA degradation, sensitive to one molecule of cDNA, has a wide dynamic range (at least seven orders of magnitude), and gives absolute quantitation of each isoform. Primer pairs specific for each PTM/target pre-mRNA combination are used. The sequence specificity ofthe assay permits the monitoring ofthe specificity ofthe trans-splicing reactions. The sensitivity and quantitative nature ofthe assay as well as the rapidity with which assays can be developed and performed is useful for the optimization of PTMs targeted against papillomaviral pre-mRNAs.

The specificity of PTM induced trans-splicing (i.e. to determine the specificity of targeted trans-splicing to HPV target pre-mRNA) is also evaluated by 5' and/or 3' rapid amplification of cDNA ends (RACE) according to standard procedures. This method is relatively fast compared to the conventional cDNA library construction, and gives complete sequences of 5' and/or 3' cDNA ends, so that the number of specific and non-specific splicing events can be determined. Initially, two cDNA libraries are constructed comprised of RNA isolated from cells co-transfected with a (i) linear PTM + HPV mini-gene target and (ii) safety PTM + HPV mini-gene target. For example, in order to identify the 5' ends ofthe trans-spliced RNAs (3' exon replacement), a 5' RACE assay is performed with a PTM antisense primer. Similarly, to identify the 3' ends ofthe trαns-spliced RNAs (5' exon replacement), a 3' RACE assay is performed using a PTM sense primer. The cDNA is amplified by PCR, digested with restriction enzymes and cloned into a plasmid vector. The cDNA clones are initially screened by colony hybridization using a PTM specific probe. From each cDNA library, positive clones are selected and sequenced, and the sequence information is used to compare the specificity of linear vs. safety PTM. This permits identification of non-specific targets that trans-splice at high frequencies. Analysis of these targets provides useful information about the sequences that are responsible for non-specific trans-splicing and helps in the construction of specific PTMs.

The trans-splicing efficiency and specificity data obtained from the analysis ofthe initial candidate PTMs in trαns-splicing assays is used to formulate and develop PTMs with optimal trαns-splicing capabilities. The optimal PTMs are analyzed using the trans-splicing assays described above.

A mouse model for papillomavirus infections using an organotypic "raft/xenograft" technique. Papillomaviruses are generally species and cell type specific. Productive infections have been established in nude mice using bovine keratinocytes and bovine papillomaviruses. In this system, keratinocytes are initially plated onto a collagen "raft" containing fibroblasts and allowed to grow to confluence in tissue culture. The keratinocytes are then infected or transfected with papillomavirus or viral genomic DNA, respectively, and allowed to grow in culture for a few days. These rafts are then grafted onto the backs of nude mice where they develop into productively infected bovine tissue. Human papillomavirus infections can be established using the same techniques combined with human papillomaviruses and keratinocytes. This system is useful for testing the in vivo efficacy of anti- papillomavirus PTMs. In addition, grafting of cervical carcinoma tissue or cervical cancer cell lines onto nude mice is used. In addition, testing can be done using several animal models including bovine papillomavirus (BPV-1), Canine oral papillomavirus (COPV), and Cottontail rabbit papillomavirus (CRPV). COPV, in particular, has served as a good model for vaccine development.

The present invention is not to be limited in scope by the specific embodiments described herein. Indeed, various modifications ofthe invention in addition to those described herein will become apparent to those skilled in the art from the foregoing description and accompanying Figures. Such modifications are intended to fall within the scope ofthe appended claims. Various references are cited herein, the disclosure of which are incoφorated by reference in their entireties.

Claims

WE CLAIM:

1. A cell comprising a nucleic acid molecule wherein said nucleic acid molecule comprises: a) one or more target binding domains wherein said target binding domain is between 10 and 600 nucleotides in length and that target binding ofthe nucleic acid molecule to a target pre- mRNA expressed within a cell; b) a 3' splice region comprising a branchpoint, a pyrimidine tract and a 3' splice acceptor site; c) a spacer region that separates the 3' splice region from the target binding domain; and d) nucleotide sequence to be trans-spliced to the target pre-mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

2. A cell comprising a nucleic acid molecule wherein said nucleic acid molecule comprises: a) one or more target binding domains wherein said target binding domain is between 10 and 600 nucleotides in length and that target binding ofthe nucleic acid molecule to a target pre- mRNA expressed within a cell b) a 5' splice site; c) - a spacer region that separates the 5' splice site from the target

binding domain; and d) a nucleotide sequence to be trans-spliced to the target pre- mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

3. The cell of claim 1 wherein the nucleic acid molecule further comprises a 5' donor site.

4. The cell of Claim 1 wherein the nucleic acid molecule further comprises a safety nucleotide sequence comprising one or more complementary sequences that bind to one or more sides ofthe 3' splice region.

5. The cell of Claim 2 wherein the nucleic acid molecule further comprises a safety nucleotide sequence comprising one or more complementary sequences that bind to one or more sides ofthe 5' splice region.

6. The cell of Claim 1 wherem the nucleic acid molecule further comprises

sequences encoding a translatable protein product.

^0

7. The cell of Claim 1 or 3 wherein the nucleic acid molecule further comprises a nucleotide sequence containing a translational stop codon.

8. A cell comprising a recombinant vector wherein said vector expresses a nucleic acid molecule comprising: a) one or more target binding domains wherein said target binding domain is between 10 and 600 nucleotides in length and that target binding of the nucleic acid molecule a target. pre-mRNA expressed within a cell; b) a 3' splice region comprising a branchpoint, a pyrimidine tract and a 3' splice acceptor site; c) a spacer region that separates the 3' splice region from the target binding domain; and d) a nucleotide sequence to be trans-spliced to the target pre-mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

9. A cell comprising a recombinant vector wherein said vector expresses a nucleic acid molecule comprising: a) one or more target binding domains wherein said target binding domain is between 10 and 600 nucleotides in length and that target

°t\ binding ofthe nucleic acid molecule a target pre-mRNA expressed within a cell; b) a 5' splice site; c) a spacer region that separates the 5' splice site from the target binding domain; and d) a nucleotide sequence to be trans-spliced to the target pre-mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

10. The cell of claim 8 wherein the nucleic acid molecule further comprises a 5' donor site.

11. A method of producing a chimeric RNA molecule in a cell comprising: contacting a target pre-mRNA expressed in the cell with a nucleic acid molecule recognized by nuclear splicing components wherein said nucleic acid molecule comprises: a) one or more target binding domains wherein said target binding domain is between 10 and 600 nucleotides in length and that target binding ofthe nucleic acid molecule to a target pre-mRNA

expressed within a cell; b) a 3' splice region comprising a branchpoint, a pyrimidine tract and

a 3' splice acceptor site; c) a spacer region that separates the 3' splice region from the target binding domain; and d) a nucleotide sequence to be trans-spliced to the target pre-mRNA; under conditions in which a portion ofthe nucleic acid molecule is trans-spliced to a portion ofthe target pre-mRNA to form a chimeric RNA within the cell.

12. A method of producing a chimeric RNA molecule in a cell comprising: contacting a target pre-mRNA expressed within the cell with a nucleic acid molecule recognized by nuclear splicing components wherein said nucleic acid molecule comprises: a) one or more target binding domains wherein said target binding domain is between 10 and 600 nucleotides in length and that target binding ofthe nucleic acid molecules target pre-mRNA expressed within a cell; b) a 5' splice site; c) a spacer region that separates the 5' splice site from the target binding domain; and d) a nucleotide sequence to be trαns-spliced to the target pre-

mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

13. A method of claim 11 wherein the nucleic acid molecule further comprises a 5' donor site.

14. The method of claim 11 , wherein the chimeric RNA molecule comprises sequences encoding a translatable protein.

15. The method of claim 11 , wherein the chimeric RNA molecule comprises sequences encoding a toxin.

16. A nucleic acid molecule comprising: a) one or more target binding domains wherein said target binding domain is between 10 and 600 nucleotides in length and that target binding ofthe nucleic acid molecule to a target pre-mRNA expressed within a cell; b) a 3' splice region comprising a branchpoint, a pyrimidine tract and a 3' splice acceptor site; c) a spacer region that separates the 3' splice region from the target binding domain; d) a safety sequence comprising one or more complementary sequences that bind to one or both sides ofthe 3' splice site; and

<N e) a nucleotide sequence to be trans-spliced to the target pre-mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

17. A nucleic acid molecule comprising : a) one or more target binding domains wherein said target binding domain is between 10 and 600 nucleotides in length and that target binding ofthe nucleic acid molecule a target pre-mRNA expressed within a cell; b) a 5' splice site; c) a spacer region that separates the 5' splice site from the target binding domain; d) a safety sequence comprising one or more complementary sequences that bind to one or both sides ofthe 5' splice site; and e) a nucleotide sequence to be trans-spliced to the target pre-mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

18. The nucleic acid molecule of claim 16 wherein the nucleic acid molecule

further comprises a 5' donor site.

19. The nucleic acid molecule of claim 16 or 17 wherein the nucleic acid molecule further comprises sequences encoding a translatable protein product.

20. The nucleic acid molecule of claim 16 or 17 wherein the translatable protein product is a toxin.

21. An expression vector wherein said vector expresses a nucleic acid molecule comprising: a) one or more target binding domains wherein said target binding domain is between 10 and 600 nucleotides in length and that target binding ofthe nucleic acid πiolecule to a target pre-mRNA expressed within a cell; b) a 3' splice region comprising a branchpoint, a pyrimidine tract and a 3' splice acceptor site; c) a spacer region that separates the 3' splice region from the target binding domain; and d) nucleotide sequence to be trans-spliced to the target pre-mRNA; wherein said nucleic acid molecule is recognized by nuclear

splicing components within the cell.

22. A eukaryotic expression vector wherein said vector expresses a nucleic acid molecule comprising: a) one or more target binding domains wherein said target binding domain is between 10 and 600 nucleotides in length and that target binding ofthe nucleic acid molecule to a target pre-mRNA expressed within a cell; b) a 5' splice site; c) a spacer region that separates the 5' splice site from the target binding domain; and d) a nucleotide sequence to be trans-spliced to the target pre- mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

23. The vector of claim 21 wherein the nucleic acid molecule further comprises a 5' donor site.

24. The expression vector of claim 21 or 22 further comprising a safety sequence comprising one or more complementary sequences that bind to one or both sides ofthe splice site.

25. A cell comprising a nucleic acid molecule wherein said nucleic acid molecule comprises: a) a 3' splice region comprising a branch point, a pyrimidine tract and a 3' splice acceptor site; and b) a nucleotide sequence to be trαns-spliced to the target pre-mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

26. A cell comprising a nucleic acid molecule wherein said nucleic acid molecule comprises: a) a 5' splice site; c) a spacer region that separates the 5' splice site from the target binding domain; and d) a nucleotide sequence to be trans-spliced to the target pre-mRNA;_ wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

27. The cell of claim 25 wherein the nucleic acid molecule further comprises a 5' donor site.

28. The cell of claim 25 or 26 wherein the nucleotide sequences to be trans- spliced to the target pre-mRNA comprises a nucleotide sequence tag.

29. A cell comprising a recombinant vector wherein said vector expresses a nucleic acid molecule comprising: a) _. a 3' splice region comprising a branchpoint, a pyrimidine tract and a 3' splice acceptor site; and b) a nucleotide sequence to be trαns-spliced to the target pre-mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

30. A cell comprising a recombinant vector wherein said vector expresses a nucleic acid molecule comprising: a) a 5' splice site; and b) a nucleotide sequence to be trαns-spliced to the target pre-mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

31. The cell of claim 29 wherein the nucleic acid molecule further comprises a 5' donor site.

32. A method of producing a chimeric RNA molecule in a cell comprising: contacting a target pre-mRNA expressed in the cell with a nucleic acid molecule recognized by nuclear splicing components wherein said nucleic acid molecule comprises:

99 a) a 3' splice region comprising a branch point, a pyrimidine tract and a 3' splice acceptor site; and b) a nucleotide sequence to be trαns-spliced to the target pre-mRNA; under conditions in which a portion ofthe nucleic acid molecule is trans-spliced to a portion ofthe target pre-mRNA to form a

L chimeric RNA within the cell.

33. A method of producing a chimeric RNA molecule in a cell comprising: contacting a target pre-mRNA expressed within the cell with a nucleic acid molecule recognized by nuclear splicing components wherein said nucleic acid molecule comprises: a) a 5' splice site; and d) a nucleotide sequence to be trαns-spliced to the target pre-mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

34. A method of claim 32 wherein the nucleic acid molecule further comprises a 5' donor site.

35. The method of claim 32, wherein the chimeric RNA molecule comprises a nucleotide sequence tag.

36. An eukaryotic expression vector wherein said vector expresses a nucleic acid molecule comprising: a) a 3' splice region comprising a branchpoint, a pyrimidine tract and

) a 3' splice acceptor site; and b) a nucleotide sequence to be trαns-spliced to the target pre-mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

37. An eukaryotic expression vector wherein said vector expresses a nucleic acid molecule comprising: a) a 5' splice site; and d) a nucleotide sequence to be trans-spliced to the target pre-mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

38. The vector of claim 36 wherein the nucleic acid molecule further comprises a 5' donor site.

39. An expression library comprising recombinant expression vectors wherein said vectors expresses a nucleic acid molecule comprising: a) a 3' splice region comprising a branchpoint, a pyrimidine tract and a 3' splice acceptor site; and d) a nucleotide sequence to be trαns-spliced to the target pre-mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

40. An expression library comprising recombinant expression vectors wherein said wherein said vector expresses a nucleic acid molecule comprising: a) a 5' splice site; and b) a nucleotide sequence to be trαns-spliced to the target pre-mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

41. The expression library of claim 39 wherein the nucleic acid molecule further comprises a 5' donor site.

42. The expression library of claim 39 or 40_|( herein the nucleotide s_jequence to be spliced to the target pre-mRNA comprises a nucleotide sequence tag.

43. A method for mapping exon-intron boundaries in pre-mRNA molecules comprising:

(i) contacting a nucleic acid molecule to a target pre-mRNA molecule,

under conditions in which a portion ofthe nucleic acid molecule is

WZ trαns-spliced to a portion ofthe target pre-mRNA to form a chimeric mRNA; (ii) amplifying the chimeric mRNA molecule; (iii) selectively purifying the amplified molecule; and (iv) determining the nucleotide sequence o the amplified molecule thereby identifying the intron-exon boundaries.

Jό^'3 ^: 4-i, A nucleic acid molecule comprising: a) two or more target binding domains that target binding ofthe pre- trans-splicing molecule to a target pre-mRNA; b) a 3' splice region comprising a branch point, a pyrimidine tract and a 3' splice acceptor site and a 5' splice donor site; c) spacer regions that separate the 3' splice region and the 5' splice donor site from the target binding domains; and d) a nucleotide sequence to be trαns-spliced to the target pre-mRNA; wherein said nucleic acid molecules is recognized by nuclear splicing components within the cell.

H5. The nucleic acid molecule of claim * wherein the spacer regions separate the 3' splice region and the 5' splice donor site from the target binding domains.

Hfc. The nucleic acid molecule of claim *W wherein the nucleic acid molecule further comprises sequences encoding a translatable protein product.

The nucleic acid molecule of claim It wherein the translatable protein product is &_ toxin.

''Ψk The nucleic acid molecule of claim 11 wherein the nucleic acid molecule further comprises sequences containing a translational stop codon.

«<.. The molecule of claim *lwherein the nucleotide sequence to be trαns- spliced to the target pre-mRNA comprises nucleotide sequences encoding the cystic fibrosis trans-membrane conductance regulator.

[04 SB. The molecule of claim wberein-the nucleotide sequences encoding the — cystic fibrosis trans-membrane conductance regulator comprise exon 10 ofthe cystic fibrosis trans-membrane regulator conductance gene.

SL A recombinant expressiofi vector wherein said vector expresses a nucleotide sequence comprising: a) two or more target binding domains that target binding ofthe pre- trans-splicing molecule to a target pre-mRNA; b) a 3' splice region comprising a branchpoint, a pyrimidine tract and a 3' splice acceptor site and a 5' splice donor site; c) spacer regions that separate the 3' splice region and the 5' splice donor site from the target binding domains; and d) a nucleotide sequence to be trαns-spliced to the target pre-mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

Si The molecule of claim «tøor S\ further comprising a safety nucleotide sequence comprising one or more complementary sequences that bind to one or more sides ofthe pre-trans-splicing molecule branch point, pyrimidine tract, 3' splice site or 5' splice site.

5J . A cell comprising a nucleic acid molecule wherein said nucleic acid molecule comprises:

a) two or more target binding domains that target binding ofthe pre- trans-splicing molecule to a target pre-mRNA; b) a 3' splice region comprising a branch point, a pyrimidine tract and a 3' splice acceptor site and a 5' splice donor site; c) spacer regions that separate the 3' splice region and the 5' splice donor site from the target binding domains; and

IDS' - ^■ d) a nucleotide sequence to be trαns-spliced to the target pre-mRNA; wherein said nucleic acid molecules is recognized by nuclear splicing components within the cell.

54 The cell of claim S}¹ wherein the spacer regions ofthe nucleic acid molecule separate the 3' splice region and the 5' splice donor site from the target binding domains.

£5 The cell of claim £J wherein the nucleic acid molecule further comprises sequences encoding a translatable protein product.

g _ The cell of claim SS wherein translatable protein is a toxin.

g^. ^• The cell of claim S3 wherein the nucleic acid molecule further comprises a nucleotide sequence containing a translational stop codon.

$φ The cell of claim S3 wherein the nucleotide sequence to be trαns-spliced to the target pre-mRNA comprises nucleotide sequences encoding the cystic fibrosis transmembrane conductance regulator.

5-j . The cell of claim ξj, wherein the nucleotide sequences encoding the cystic fibrosis transmembrane conductance regulator comprise exon 10 cystic fibrosis transmembrane conductance regulator gene.

, A cell comprising a recombinant expression vector wherein said vector expresses a nucleotide sequence comprising: a) two or more target binding domains that target binding ofthe pre- trαns-splicing molecule to a target pre-mRNA; b) a 3' splice region comprising a branchpoint, a pyrimidine tract and

a 3' splice acceptor site and a 5' splice donor site; c) spacer regions that separate the 3' splice region and the 5' splice donor site from the target binding domains; and d) a nucleotide sequence to be trαns-spliced to the target pre-mRNA; wherein said nucleic acid molecules is recognized by nuclear splicing components within the cell.

X,

%.. A cell comprising the nucleic acid molecule of claim or 5| further comprising a safety nucleotide sequence comprising one or more complementary sequences that bind to one or more sides ofthe pre-tr ns-splicing molecule branch point, pyrimidine tract, 3' splice site or 5' splice site.

j -, A method of producing a chimeric mRNA molecule comprising contacting a pre-trans-splicing molecule with a target pre-mRNA under conditions in which a double trαns- splicing reaction results in a portion ofthe pre-trαns-splicing molecule being trαns-spliced to a portion of the target pre-mRNA to form said chimeric mRNA.

_|,3_#1 The method of claim (A wherein the pre-trαns-splicing mRNA comprises nucleotide sequences encoding the cystic fibrosis transmembrane conductance regulator.

. The method of claim 63, wherein the pre-trαns-splicing mRNA comprises exon 10 cystic fibrosis transmembrane conductance regulator gene.

:$$, A method of providing a host cell with a chimeric mRNA molecule, said method comprising: transferring a pre-trαns-splicing molecule to a host cell expressing a target pre-mRNA wherein the pre-trαns-splicing molecule binds to the target pre-mRNA under conditions in which a double trαns-splicing reaction results in a portion ofthe pre-trans-splicing molecule being trαns-spliced to a portion ofthe target pre-mRNA to form said chimeric mRNA. (&. The method of claim 63¹ wherein the host cell is a human cell.

tø The method of claim (β wherein the pre-trαns-splicing molecule comprises nucleotide sequences encoding a protein that is defective or lacking in the host cell.

6$. The method of claim 6ξTwherein the pre-trαns-splicing molecule comprises nucleotide sequences encoding a fragment ofthe cystic fibrosis trans-membrane regulator protein.

. t>°l. A pharmaceutical composition comprising the nucleic acid molecule of claim 1 and a pharmaceutically acceptable carrier.

J0. A nucleic acid molecule comprising: a) one or more target binding domains that target binding of the pre- trαns-splicing molecule to a target pre-mRNA; b) a 5' splice donor site; c) a spacer region that separates the 5' splice donor site from the target binding domain; and d) a nucleotide sequence comprising the 5' end of a gene to be trans- spliced to the target pre-mRNA; wherein said nucleic acid molecules is recognized by nuclear splicing components within the cell.

?J . The nucleic acid molecule of claim 70 wherein the nucleotide sequence to be the trαns-spliced to the target pre-mRNA encodes a translatable protein product.

J3 The nucleic acid molecule of claim l wherein the translatable protein product is a toxin.

108 — _I 3_ The nucleic acid molecule of claim ?0 wherein the nucleotide sequence to be the trαns-spliced to the target pre-mRNA comprises a translational stop codon.

?^. The nucleic acid molecule of claim H wherein the nucleotide sequence to be trαns-spliced to the target pre-mRNA comprises nucleotide sequences encoding the cystic fibrosis transmembrane conductance regulator.

fg The nucleic acid molecule of claim ? wherein the nucleotide sequences encoding the cystic fibrosis transmembrane conductance regulator comprise exons 1-10 cystic fibrosis transmembrane regulator gene.

Η. A recombinant expression vector wherein said vector expresses a nucleotide sequence comprising a) one or more target binding domains that target binding ofthe pre- trαns-splicing molecule to a target pre-mRNA; b) a 5' splice donor site; c) a spacer region that separates the 5' splice donor site from the target binding domain; and d) a nucleotide sequence comprising the 5' end of a gene to be trαns- spliced to the target pre-mRNA; wherein said nucleic acid molecules is recognized by nuclear splicing components within the cell.

?}. The molecule of claim W or 13 further comprising a safety nucleotide sequence comprising one or more complementary sequences that bind to one or more sides ofthe pre-trαns-splicing molecule branch point, pyrimidine tract, or 3' splice site.

?8. The recombinant expression vector of claim ffe further comprising a safety nucleotide sequence comprising one or more complementary sequences that bind to one or more

1 0*1 ill

sides of the pre-trαns-splicing molecule branch point, pyrimidine tract, or 3' splice site.

fi , A cell comprising a nucleic acid molecule wherein said nucleic acid molecule comprises:

a) one or more target binding domains that target binding of the pre- trαns-splicing molecule to a target pre-mRNA; b) a 5' splice donor site; c) a spacer region that separates the 5' splice donor site from the target binding domain; and d) a nucleotide sequence comprising the 5' end of a gene to be trαns- spliced to the target pre-mRNA; wherein said nucleic acid molecules is recognized by nuclear splicing components within the cell.

$ϋ. The cell of claim :M wherein the nucleic acid molecule further comprises sequences encoding a translatable protein product.

#|. The cell of claim .^'?! wherein the nucleic acid molecule further comprises a nucleotide sequence containing a translational stop codon.

f? ... The cell of claim ^*M wherein the nucleotide sequence to be trαns-spliced to the target pre-mRNA comprises nucleotide sequences encoding the cystic fibrosis transmembrane regulator.

a* The cell of claim 79 wherein the nucleotide sequences encoding the cystic fibrosis trans-membrane regulator comprise exons 1-10 of the cystic fibrosis transmembrane regulator gene.

i . The cell of claim H wherein the translatable protein is a toxin. no $5. A cell comprising a recombinant expression vector wherein said vector expresses a nucleotide sequence comprising: a) one or more target binding domains that target binding ofthe pre- trans-splicing molecule to a target pre-mRNA; b) a 5' splice donor site; c) a spacer region that separates the 5' splice donor site from the target binding domain; and d) a nucleotide sequence comprising the 5' end of a gene to be trαns- spliced to the target pre-mRNA; wherein said nucleic acid molecules is recognized by nuclear splicing components within the cell.

, A cell comprising the nucleic acid molecule of claim 39 or fi further comprising a safety nucleotide sequence comprising one or more complementary sequences that bind to one or more sides ofthe pre-trαns-splicing molecule branchpoint, pyrimidine tract; or 5' splice site.

g^ A cell comprising the recombinant expression vector of claim % further comprising a safety nucleotide sequence comprising one or more complementary sequences that bind to one or more sides ofthe pre-trans-splicing molecule branchpoint, pyrimidine tract, or 5' splice site.

Ϋ£_t A method of producing a chimeric mRNA molecule comprising contacting a pre-trαns-splicing molecule with a target pre-mRNA under conditions in which a trαns-splicing reaction results in a portion ofthe pre-trαns-splicing molecule being trαns-spliced to the 5' end of the target pre-mRNA to form said chimeric mRNA.

£<j_ The method of claim & wherein the pre-trαns-splicing mRNA comprises nucleotide sequences encoding the cystic fibrosis transmembrane conductance regulator.

A. The method of claim wherein the pre-trαns-splicing mRNA comprises exons 1-10 of the cystic fibrosis transmembrane conductance regulator gene.

l. A method of providing a host cell with a chimeric mRNA molecule, said method comprising: transferring a pre-trαns-splicing molecule to a host cell expressing a target pre-mRNA wherein the pre-trαns-splicing molecule binds to the target pre-mRNA under conditions in which a trαns-splicing reaction results in a portion ofthe pre-trans-splicing molecule being trαns-spliced to a 5' portion ofthe target pre-mRNA to form said chimeric mRNA.

<fø The method of claim 1\ wherein the host cell is a human cell.

άi The method of claim 1 wherein the pre-trαns-splicing molecule comprises nucleotide sequences encoding a protein that is defective or lacking in the host cell.

φj. The method of claim 43 wherein the pre-trαns-splicing molecule comprises nucleotide sequences encoding a fragment ofthe cystic fibrosis transmembrane conductance regulator protein.

ήg A pharmaceutical composition comprising the nucleic acid molecule of claim 27 and a pharmaceutically acceptable carrier.

46. A nucleic acid molecule wherein said nucleic acid molecule is CFTR PTM24.

^■ l λ f. A plant cell comprising a nucleic acid molecule wherein said nucleic acid molecule comprises: a) one or more target binding domains wherein that target binding of the nucleic acid molecule to a target pre-mRNA expressed within a cell; b) a 3' splice region comprising a 3' splice acceptor site; c) a spacer region that separates the 3' splice region from the target binding domain; and d) a nucleotide sequence to be trαns-spliced to the target pre-mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell. _

. A plant cell comprising a nucleic acid molecule wherein said nucleic acid molecule comprises: a) one or more target binding domains that target binding domain of the nucleic acid molecule to a target pre-mRNA expressed within a plant cell; b) a 5' splice site; c) a spacer region that separates the 5' splice site from the target binding domain; and

113 d) a nucleotide sequence to be trαns-spliced to the target pre- mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

^ . The plant cell of claim 4.-wherein the nucleic acid molecule further comprises a 5' donor site.

løø. The plant cell of claim 4} wherein the nucleic acid molecule further comprises a UA rich sequence.

!_»!• The plant cell of Claim 43-wherein the nucleic acid molecule further comprises a safety nucleotide sequence comprising one or more complementary sequences that bind at or adjacent to one or more sides of the 3' splice region.

I l The plant cell of Claim % wherein the nucleic acid molecule further comprises a safety sequence comprising one or more complementary sequences that bind at or adjacent to one or more sides ofthe 5' splice region.

114

103. The plant cell of Claim 4> wherein the nucleic acid molecule further comprises sequences encoding a translatable protein product.

I04. The plant cell of Claim wvherein the nucleic acid molecule further comprises a nucleotide sequence containing a translational stop codon.

105. A plant cell comprising a recombinant vector wherein said vector expresses a nucleic acid molecule comprising: a) one or more target binding domains that target binding domairipf the nucleic acid molecule to a target pre- mRNA expressed within a plant cell; b) . a 3' splice region comprising a 3' splice acceptor site: c) a spacer region that separates the 3' splice region from the target binding domain; and d) a nucleotide sequence to be rrαns-spliced to the target pre-mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

.106. A cell comprising a recombinant vector wherein said vector expresses a nucleic acid molecule comprising:

\S a) one or more target binding domains that target binding domain of the nucleic acid molecule to a target pre-mRNA expressed within a plant cell; b) a 5' splice site; c) a spacer region that separates the 5' splice site from the target binding domain; and d) a nucleotide sequence to be trαns-spliced to the target pre- mRNA; wherein said nucleic acid molecule is recognized by nuclear' splicing components within the cell.

I of- The cell of claim !&f wherein the nucleic acid molecule further comprises a 5' donor site.

I|?0 The cell of claim l&Jwherein the nucleic acid molecule further comprises a UA rich sequence.

IM. A method of producing a chimeric RNA molecule in a plant cell comprising: contacting a target pre-mRNA expressed in the cell with a nucleic acid molecule recognized by nuclear splicing components wherein said nucleic acid molecule comprises:

l i b a) one or more target binding domains that target binding domain of the nucleic acid molecule to a target pre-mRNA expressed within a plant cell; b) a 3' splice region comprising a 3' splice acceptor site; c) a spacer region that separates the 3' splice region from the target binding domain; and d) a nucleotide sequence to be trans-spliced to the target pre-mRNA; under conditions in which a portion ofthe nucleic acid molecule is trans-spliced to a portion ofthe target pre-mRNA to form a chimeric RNA within the cell.

j|0. A method of producing a chimeric RNA molecule in a plant cell comprising: contacting a target pre-mRNA expressed within the cell with a nucleic acid molecule recognized by nuclear splicing components wherein said nucleic acid molecule comprises: a) one or more target binding domains that target binding domain of the nucleic acid molecule to a target pre-mRNA expressed within a plant cell; b) a 5' splice site; c) a spacer region that separates the 5' splice site from the target binding domain; and

I IT- d) a nucleotide sequence to be trαns-spliced to the target pre-mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

111. The method of claim 1*1 wherein the nucleic acid molecule further comprises a 5' donor site.

IH. The method of claim ϊtr) wherein the nucleic acid molecule further comprises a UA rich sequence.

113. The method of claim ItA, wherein the chimeric RNA molecule comprises sequences encoding a translatable protein.

I IH. The method of claim llή, wherein the chimeric RNA molecule comprises sequences encoding a toxin.

US. A nucleic acid molecule comprising: a) one or more target binding domains that target binding domain of the nucleic acid molecule to a target pre-mRNA expressed within a plant cell; b) a 3' splice region comprising a 3' splice acceptor site;

m c) a spacer region that separates the 3' splice region from the target binding domain; d) a safety sequence comprising one or more complementary sequences that bind at or adjacent to one or both sides ofthe 3' splice site; and e) a nucleotide sequence to be trαns-spliced to the target pre- mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

I !&• A nucleic acid molecule comprising : a) one or more target binding domains that target binding domain of the nucleic acid molecule to a target pre-mRNA expressed within a plant cell; b) a 5' splice site; c) a spacer region that separates the 5' splice site from the target binding domain; d) a safety sequence comprising one or more complementary sequences that bind at or adjacent to one or both sides ofthe 5' splice site; and

i e) a nucleotide sequence to be trαns-spliced to the target pre- mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

Ill The nucleic acid molecule of claim US wherein the nucleic acid molecule further comprises a 5' donor site.

Ilβ. The nucleic acid molecule of claim lib further comprising a safety sequence comprising one or more complementary sequences that bind at or adjacent to one or both sides of the 3' splice site.

114, The nucleic acid molecule of claim IIS or lib wherein the nucleic acid molecule further comprises a UA rich sequence.

llO A eukaryotic expression vector wherein said vector expresses a nucleic acid molecule comprising: a) one or more target binding domains that target binding domain of the nucleic acid molecule to a target pre-mRNA expressed within a plant cell; b) a 3' splice region comprising a 3' splice acceptor site; c) a spacer region that separates the 3' splice region from the target binding domain; and

o d) a nucleotide sequence to be trαns-spliced to the target pre-mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

i l. A eukaryotic expression vector wherein said vector expresses a nucleic acid molecule comprising: a) one or more target binding domains that target binding domain of the nucleic acid molecule to a target pre-mRNA expressed within a plant cell; b) a 5' splice site; c) a spacer region that separates the 5' splice site from the target binding domain: and d) a nucleotide sequence to be trαns-spliced to the target pre-mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

IXX. The vector of claim IID wherein the nucleic acid molecule further comprises a 5' donor site.

3. The vector of claim 110 or H\ wherein the nucleic acid molecule further

comprises a UA rich sequence. jjtø A nucleic acid molecule comprising. a) one or more target binding domains that target binding domain of the nucleic acid molecule to a target pre-mRNA expressed within a cell wherein said target binding domian comprises random nucleotide sequences; b) a 5' splice site; c) a spacer region that separates the 5' splice site from the target binding domain; and d) a nucleotide sequence to be trαns-sphced to the target pre-mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

Uλ

125. A cell comprising a nucleic acid molecule wherein said nucleic acid molecule comprises: a) one or more target binding domains that target binding of the nucleic acid molecule to a factor VIII or papilloma virus pre-mRNA expressed within the cell; b) a 3' splice region comprising a branch point, a pyrimidine tract and a 3' splice acceptor site; c) a spacer region that separates the 3' splice region from the target binding domain; and d) a nucleotide sequence to be trans-spliced to the target pre- mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

126. A cell comprising a nucleic acid molecule wherein said nucleic acid molecule comprises: a) one or more target binding domains that target binding of the nucleic acid molecule to a factor VUI or papilloma virus pre-mRNA expressed within the cell; b) a 3' splice acceptor site; c) a spacer region that separates the 3' splice region from the target binding domain; and

13.3 d) a nucleotide sequence to be trans-spliced to the target pre- mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

127 A cell comprising a nucleic acid molecule wherein said nucleic acid molecule comprises: a) one or more target binding domains that target binding of the nucleic acid molecule to a factor VIII or papilloma virus pre-mRNA expressed within the cell; b) a 5' sphce site; c) a spacer region that separates the 5' splice site from the target binding domain; and d) a nucleotide sequence to be trans-spliced to the target pre- mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

128. The cell of claim 125 wherein the nucleic acid molecule further comprises a 5' donor site.

Jan

129. The cell of Claim 125 wherein the nucleic acid molecule further comprises a safety nucleotide sequence comprising one or more complementary sequences that bind to one or more sides ofthe 3' splice region.

130. The cell of Claim 125 wherein the binding ofthe nucleic acid molecule to the target pre-mRNA is mediated by complementary, triple helix formation, or protein-nucleic acid interaction.

131. The cell of Claim 125 wherein the nucleotide sequences to be trans- spliced to the target pre mRNA encode a factor VIII polypeptide or papilloma virus polypeptide.

132. The cell of claim 125 wherein the papilloma virus is an oncogenic papilloma virus.

133. The cell of claim 125 wherein the nucleotide sequences to be trans- spliced to the target pre-mRNA encodes exons 23-26 of canine or human factor VIII protein or exons 16-26 of murine human factor VJJI protein.

134. A cell comprising a recombinant vector wherein said vector expresses a nucleic acid molecule comprising: a) one or more target binding domains that target binding of the nucleic acid molecule to a factor VIII or papilloma virus pre-mRNA expressed within the cell; 5 b) a 3' splice region comprising a branch point, a pyrimidine tract and a 3' splice acceptor site; c) a spacer region that separates the 3' splice region from the target binding domain; and d) a nucleotide sequence to be trans-spliced to the target pre- mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

135. A cell comprising a recombinant vector wherein said vector expresses a nucleic acid molecule comprising: a) one or more target binding domains that target binding of the nucleic acid molecule to a factor VIII or papilloma virus pre-mRNA expressed within the cell; b) a 3' splice acceptor site; c) a spacer region that separates the 3' splice region from the target binding domain; and d) a nucleotide sequence to be trans-spliced to the target pre- mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

136. A cell comprising a recombinant vector wherein said vector expresses a nucleic acid molecule comprising:

IX, a) one or more target binding domains that target binding of the nucleic acid molecule to a factor VIII or papilloma virus pre-mRNA expressed within the cell; b) a 5' splice site; c) a spacer region that separates the 5' splice site from the target binding domain; and d) a nucleotide sequence to be trans-spliced to the target pre- mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

137. The cell of claim 134 wherein the nucleic acid molecule further comprises a 5' donor site.

138. A method of producing a chimeric RNA molecule in a cell comprising: contacting a target pre-mRNA expressed in the cell with a nucleic acid molecule recognized by nuclear splicing components wherem said nucleic acid molecule comprises: a) one or more target binding domains that target binding of the nucleic acid molecule to a factor VIII or papilloma virus pre-mRNA expressed within the cell; b) a 3' splice region comprising a branch point, a pyrimidine tract and a 3' splice acceptor site; c) a spacer region that separates the 3' splice region from the target binding domain; and d) a nucleotide sequence to be trans-spliced to the target pre- mRNA; under conditions in which a portion ofthe nucleic acid molecule is trans- spliced to a portion ofthe target pre-mRNA to form a chimeric RNA within the cell.

139. A method of producing a chimeric RNA molecule in a cell comprising: contacting a target pre-mRNA expressed in the cell with a nucleic acid molecule recognized by nuclear splicing components wherein said nucleic acid molecule comprises: a) one or more target binding domains that target binding of the nucleic acid molecule to a factor VIII or papilloma virus pre-mRNA expressed within the cell; b) a 3' splice acceptor site; c) a spacer region that separates the 3' splice region from the target binding domain; and d) a nucleotide sequence to be trans-spliced to the target pre- mRNA; under conditions in which a portion ofthe nucleic acid molecule is trans-spliced to a portion ofthe target pre- mRNA to form a chimeric RNA within the cell.

140. A method of producing a chimeric RNA molecule in a cell comprising: contacting a target pre-mRNA expressed within the cell with a nucleic acid molecule recognized by nuclear splicing components wherein said nucleic acid molecule comprises: a) one or more target binding domains that target binding of the nucleic acid molecule to a factor VIII or papilloma virus pre-mRNA expressed within the cell; b) a 5' splice site; c) a spacer region that separates the 5' splice site from the target binding domain; and d) a nucleotide sequence to be trans-spliced to the target pre- mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

141. A method of claim 138 wherein the nucleic acid molecule further comprises a 5' donor site.

142. The method of claim 138, wherein the chimeric RNA molecule comprises sequences encoding a translatable protein.

143. A nucleic acid molecule comprising: a) one or more target binding domains that target binding of the nucleic acid molecule to a factor VIIJ or papilloma virus pre-mRNA expressed within the cell; b) a 3' splice region comprising a branch point, a pyrimidine tract and a 3' splice acceptor site; c) a spacer region that separates the 3' splice region from the target binding domain; d) a safety sequence comprising one or more complementary sequences that bind to one or both sides ofthe 3' splice site; and e) a nucleotide sequence to be trans-spliced to the target pre- mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

144. A nucleic acid molecule comprising: a) one or more target binding domains that target binding of the nucleic acid molecule to a factor VIII or papilloma virus pre-mRNA expressed within the cell; b) a 3' splice acceptor site; c) a spacer region that separates the 3' splice region from the target binding domain;

130 d) a safety sequence comprising one or more complementary sequences that bind to one or both sides ofthe 3' splice site; and e) a nucleotide sequence to be trans-spliced to the target pre- mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

145. A nucleic acid molecule comprising : a) one or more target binding domains that target binding of the nucleic acid molecule to a factor VIII or papilloma virus pre-mRNA expressed within the cell; b) a 5' splice site; c) a spacer region that separates the 5' splice site from the target binding domain; d) a safety sequence comprising one or more complementary sequences that bind to one or both sides ofthe 5' splice site; and e) a nucleotide sequence to be trαns-spliced to the target pre- mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

131

146. The nucleic acid molecule of claim 18 wherein the nucleic acid molecule further comprises a 5' donor site.

147. The nucleic acid molecule of claim 143 wherein the binding ofthe nucleic acid molecule to the target pre-mRNA is mediated by complementary, triple helix formation, or protein-nucleic acid interaction.

148. The nucleic acid molecule of claim 143 wherein the nucleotide to be trαns-spliced to the target pre-mRNA encodes a translatable factor VUI polypeptide or papilloma virus polypeptide and/or a marker protein.

149. The nucleic acid molecule of claim 143 wherein the papilloma virus is an oncogenic papilloma virus.

150. The nucleic acid molecule of claim 149 wherein the papilloma virus is papilloma virus 16.

151. The nucleic acid molecule of claim 145 wherein the papilloma virus is an oncogenic papilloma virus

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152. The nucleic acid molecule of claim 145 wherein the human papilloma virus is an oncogenic virus.

153. The nucleic acid molecule of claim 143 wherein the nucleotide sequence to be trans-spliced to the target pre mRNA encodes exons 23-26 of canine or human factor VIII protein or exons 16-26 of murine huamn factor VII protein.

154. The nucleic acid molecule of claim 145 wherein the binding ofthe nucleic acid molecule to the target pre-mRNA is mediated by complementary, triple l elix formation, or a protein-nucleic acid interaction.

155. The nucleic acid molecule of claim 145 wherein the nucleotide sequence to be trαns-spliced to the target pre-mRNA encodes a factor VIII polypeptide and/Or marker gene sequence.

156. The nucleic acid molecule of claim 145 wherein the nucleotide sequence to be trans-spliced to the target pre-mRNA encodes exons 23-26 ofthe factor VUI protein.

157. A eukaryotic expression vector wherein said vector expresses a nucleic acid molecule comprising: a) one or more target binding domains that target binding of the nucleic acid molecule to a factor VEI or papilloma virus protein pre-mRNA expressed within the cell; 133 b) a 3' splice region comprising a branch point, a pyrimidine tract and a 3' splice acceptor site; c) a spacer region that separates the 3' splice region from the target binding domain; and d) a nucleotide sequence to be trans-spliced to the target pre- mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

158. A eukaryotic expression vector wherein said vector expresses a nucleic acid molecule comprising: a) one or more target binding domains that target binding of the nucleic acid molecule to factor VIII or papilloma virus protein pre-mRNA expressed within the cell; b) a 3' splice acceptor site; c) a spacer region that separates the 3' splice region from the target binding domain; and d) a nucleotide sequence to be trans-spliced to the target pre- mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

159. A eukaryotic expression vector wherein said vector expresses a nucleic acid molecule comprising:

'31 a) one or more target binding domains that target binding of the nucleic acid molecule to a factor VIII polypeptide or papilloma virus protein pre-mRNA expressed within the cell; b) a 5' sphce site; c) a spacer region that separates the 5' splice site from the target binding domain; and d) a nucleotide sequence to be trans-spliced to the target pre- mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

160. The vector of claim 157 wherein the nucleic acid molecule further comprises a 5' donor site.

161. The vector of claim 157 wherein said vector is a viral vector.

162. The vector of claim 161 wherein in said viral vector is an adeno- associated viral vector.

163. A composition comprising a physiologically acceptable carrier and a nucleic acid molecule according to any of claims 157-162.

135^"

164. A cell comprising a nucleic acid molecule wherein said nucleic acid molecule comprises: a) one or more target binding domains that target binding of the nucleic acid molecule to a viral pre-mRNA expressed within the cell; b) a 3' splice region comprising a branch point, a pyrimidine tract and a 3' splice acceptor site; c) a spacer region that separates the 3' splice region from the target binding domain; and d) a nucleotide sequence to be trans-spliced to the target pre- mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

165. A method for inhibiting the expression of papilloma virus pre-mRNA in a subject having cervical carcinoma comprising administering to said subject a nucleic acid molecule comprising: a) one or more target binding domains that target binding ofthe nucleic acid molecule to a papilloma virus pre-mRNA expressed within the cell; and b) a nucleotide sequence to be trαns-spliced to the target pre-mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

134.

166. A cell comprising a recombinant vector wherein said vector expresses a nucleic acid molecule comprising: a) one or more target binding domains that target binding of the nucleic acid molecule to a papilloma virus pre-mRNA expressed within the cell; b) a 3' splice acceptor site; and c) a nucleotide sequence to be trans-spliced to the target pre- mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

167. A cell comprising a recombinant vector wherein said vector expresses a nucleic acid molecule comprising: a) one or more target binding domains that target binding of the nucleic acid molecule to a papilloma virus pre-mRNA expressed within the cell; b) a 5' splice site; and c) a nucleotide sequence to be trans-spliced to the target pre- mRNA; wherein said nucleic acid molecule is recognized by nuclear splicing components within the cell.

168. A method of producing a chimeric RNA molecule in a cell comprising:

137- contacting a target pre-mRNA expressed in the cell with a nucleic acid molecule recognized by nuclear splicing components wherein said nucleic acid molecule comprises: a) one or more target binding domains that target binding of the nucleic acid molecule to a papilloma virus pre-mRNA expressed within the cell; b) a 3' splice acceptor site; and c) a nucleotide sequence to be trans-spliced to the target pre- mRNA; under conditions in which a portion ofthe nucleic acid molecule is trans-spliced to a portion ofthe target pre- mRNA to form a chimeric RNA within the cell.

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