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At least 973 records · Page 54Linked to original sources

PubMed2006

Stabilization of the tau exon 10 stem loop alters pre-mRNA splicing.

Neurofibrillary tangles containing filaments of the microtubule-associated protein tau are found in a variety of neurodegenerative diseases. Mutations in the tau gene itself cause frontotemporal dementia with parkinsonism, demonstrating the critical role of tau in pathogenesis. Many of these mutations in tau are silent, are found at the 5'-splice site of exon 10, and lead to increased inclusion of exon 10. These silent mutations are predicted to destabilize a stem loop structure at the exon 10 5'-splice site; however, the existence of this stem loop under physiological conditions and its role in splice regulation are controversial. Here we show that base changes that stabilize this stem loop in vitro substantially decrease exon 10 inclusion in a wild type tau minigene and rescue the increase in exon 10 splicing caused by a dementia-causing point mutation. Moreover, we probed the intracellular structure of the tau stem loop with antisense RNA and demonstrate that the stability of the stem loop dictates antisense effectiveness. Together these results validate the stem loop as a bona fide structure regulating tau exon 10 splicing.

Exons↗

PubMed2000

An intronic downstream enhancer promotes 3' splice site usage of a neural cell-specific exon.

The human nonmuscle myosin heavy chain B gene contains a 30-nucleotide alternative exon, N30, that is included in the mRNA from neural cells but is skipped in all other cells. We have previously identified an intronic distal downstream enhancer (IDDE) region that is required for neural cell-specific inclusion of N30. In this study, we investigated the mechanism by which the IDDE promotes N30 exon usage. In vitro splicing analysis using neural cell nuclear extracts and two-exon pre-mRNA substrates, which consist of the N30 exon and either the upstream (E5) or downstream (E6) exon, demonstrates that the IDDE activates upstream E5-N30 splicing by facilitating early prespliceosome complex formation. The IDDE has no effect on N30-E6 splicing where the IDDE resides. Inspection of splice site consensus sequences shows that a polypyrimidine (Py) tract preceding N30 is suboptimal for U2AF binding. Optimizing the Py tract completely relieves the requirement for the IDDE in E5-N30 splicing in vitro. In transfected cells, the wild-type minigene transcripts, which consist of three exons, E5, N30, and E6, undergo neural cell-specific and IDDE-dependent alternative splicing of N30. Optimizing the Py tract in minigenes also completely relieves the requirement for the IDDE in N30 inclusion. Furthermore, overexpression of the truncated U2AF65, which contains the arginine and serine dipeptide-rich domain and linker domain, but lacks the RNA binding domain, selectively inhibits the IDDE-mediated N30 inclusion in mRNA from the wild-type minigene in a dominant negative fashion. These results support the hypothesis that the IDDE facilitates the recognition of the 3' splice site preceding N30 by a network of protein-protein interactions implicated in the recruitment of U2AF to a suboptimal Py tract.

Enhancer Elements, Genetic↗

PubMed2000

Aspartyl beta -hydroxylase (Asph) and an evolutionarily conserved isoform of Asph missing the catalytic domain share exons with junctin.

The mouse aspartyl beta-hydroxylase gene (Asph, BAH) has been cloned and characterized. The mouse BAH gene spans 200 kilobase pairs of genomic DNA and contains 24 exons. Of three major BAH-related transcripts, the two largest (6,629 and 4,419 base pairs) encode full-length protein and differ only in the use of alternative polyadenylation signals. The smallest BAH-related transcript (2,789 base pairs) uses an alternative 3' terminal exon, resulting in a protein lacking a catalytic domain. Evolutionary conservation of this noncatalytic isoform of BAH (humbug) is demonstrated in mouse, man, and Drosophila. Monoclonal antibody reagents were generated, epitope-mapped, and used to definitively correlate RNA bands on Northern blots with protein species on Western blots. The gene for mouse junctin, a calsequestrin-binding protein, was cloned and characterized and shown to be encoded from the same locus. When expressed in heart tissue, BAH/humbug preferably use the first exon and often the fourth exon of junctin while preserving the reading frame. Thus, three individual genes share common exons and open reading frames and use separate promoters to achieve differential expression, splicing, and function in a variety of tissues. This unusual form of exon sharing suggests that the functions of junctin, BAH, and humbug may be linked.

Amino Acid Sequence↗

PubMed2001

Role of exon 2-encoded beta -domain of the von Hippel-Lindau tumor suppressor protein.

Sporadic clear cell renal carcinomas frequently harbor inactivating mutations in exon 2 of the von Hippel-Lindau (VHL) tumor suppressor gene. Here, we examine the effect of the loss of exon 2-encoded beta-domain function on VHL biochemical properties. Exon 2-encoded residues are required for VHL-mediated NEDD8 conjugation on cullin-2 and assembly with hypoxia-inducible factor alpha (HIFalpha) and fibronectin. These residues are not essential for VHL ability to assemble with elongin BC/cullin-2, to display E3 ubiquitin ligase activity in vitro and to confer energy-dependent nuclear import properties to a reporter protein. Localization studies in HIF-1alpha-null embryonic cells suggest that exon 2-encoded beta-domain mediates transcription-dependent nuclear/cytoplasmic shuttling of VHL independently of assembly with HIF-1alpha and oxygen concentration. Exon 3-encoded alpha-helical domain is required for VHL complex formation with BC/cullin-2 and E3 ubiquitin ligase activity, for binding to HIFalpha/fibronectin, but this domain is not essential for transcription-dependent nuclear/cytoplasmic trafficking. VHL(-/-) renal carcinoma cells expressing beta-domain mutants failed to produce an extracellular fibronectin matrix and to degrade HIFalpha, which accumulated exclusively in the nucleus of normoxic cells. These results demonstrate that exon 2-encoded residues are involved in two independent functions: substrate protein recognition and transcription-dependent nuclear/cytoplasmic trafficking. They also suggest that beta-domain mutations inactivate VHL function differently than alpha-domain mutations, potentially providing an explanation for the relationship between different mutations of the VHL gene and clinical outcome.

Adenoviridae↗

PubMed2001

Plasminogen activator inhibitor type 2 contains mRNA instability elements within exon 4 of the coding region. Sequence homology to coding region instability determinants in other mRNAs.

Plasminogen activator inhibitor type 2 (PAI-2) is a serine protease inhibitor that inhibits urokinase. Constitutive and regulated PAI-2 gene expression involves post-transcriptional events, and an AU-rich mRNA instability motif within the 3'-untranslated region of PAI-2 mRNA is required for this process (Maurer, F., Tierney, M., and Medcalf, R. L. (1999) Nucleic Acids Res. 27, 1664-1673). Here we show that instability determinants are present within various exons of the PAI-2 coding region, most notably within exon 4. Deletion of exon 4 from the full-length PAI-2 cDNA results in a doubling in the half-life of PAI-2 mRNA, whereas a 28-nucleotide region within exon 4 contains binding sites for cytoplasmic proteins. Inducible stabilization of PAI-2 mRNA in HT-1080 cells treated with phorbol ester and tumor necrosis factor does not alter the binding of proteins to the exon 4 instability determinant, but resulted in a transient increase in the binding of factors to the AU-rich RNA instability element. Hence, PAI-2 mRNA stability is influenced by elements located within both the coding region and the 3'-untranslated region and that cytoplasmic mRNA binding factors may influence steady state and inducible PAI-2 mRNA expression. Finally a 10-nucleotide region flanking the exon 4 protein-binding site is homologous to instability elements within five other transcripts, suggesting that a common coding region determinant may exist.

3' Untranslated Regions↗

PubMed2001

Isolation and characterization of two novel forms of the human prolactin receptor generated by alternative splicing of a newly identified exon 11.

We have identified a novel exon 11 of the human prolactin receptor (hPRLR) gene that is distinct from its rodent counterparts and have demonstrated the presence of two novel short forms of the hPRLR (S1(a) and S1(b)), which are derived from alternative splicing of exons 10 and 11. S1(a) encodes 376 amino acids (aa) that contain partial exon 10 and a unique 39-aa C-terminal region encoded by exon 11. S1(b) encodes 288 aa that lack the entire exon 10 and contains 3 amino acids at the C terminus derived from exon 11 using a shifted reading frame. These short forms, which were found in several normal tissues and in breast cancer cell lines, were expressed as cell surface receptors and possessed binding affinities comparable with the long form. Unlike the long form, neither short form was able to mediate the activation of the beta-casein gene promoter induced by prolactin. Instead they acted as dominant negative forms when co-expressed with the long form in transfected cells. Due to a marked difference in the cellular levels between the two short forms in transfected cells, S1(b) was more effective in inhibiting the prolactin-induced activation of the beta-casein gene promoter mediated by the long form of the receptor. The low cellular level of S1(a) was due to its more rapid turnover than the S1(b) protein. This is attributable to specific residues within the C-terminal unique 39 amino acids of the S1(a) form and may represent a new mechanism by which the hPRLR is modulated at the post-translational level. Since both short forms contain abbreviated cytoplasmic domains with unique C termini, they may also exhibit distinct signaling pathways in addition to modulating the signaling from the long form of the receptor. These receptors may therefore play important roles in the diversified actions of prolactin in human tissues.

Alternative Splicing↗

PubMed2002

The protein kinase C beta II exon confers mRNA instability in the presence of high glucose concentrations.

Previous studies showed that short term exposure of cells to high glucose destabilized protein kinase C (PKC) betaII mRNA, whereas PKCbetaI mRNA levels remained unaltered. Because PKCbeta mRNAs share common sequences other than the PKCbetaII exon encoding a different carboxyl terminus, we examined PKCbetaII mRNA for a cis-acting region that could confer glucose-induced destabilization. A beta-globin/growth hormone reporter con struct containing the PKCbetaII exon was transfected into human aorta and rat vascular smooth muscle cells (A10) to follow glucose-induced destabilization. Glucose (25 mm) exposure destabilized PKCbetaII chimeric mRNA but not control mRNA. Deletion analysis and electrophoretic mobility shift assays followed by UV cross-linking experiments demonstrated that a region introduced by inclusion of the betaII exon was required to confer destabilization. Although a cis-acting element mapped to 38 nucleotides within the betaII exon was necessary to bestow destabilization, it was not sufficient by itself to confer complete mRNA destabilization. Yet, in intact cells antisense oligonucleotides complementary to this region blocked glucose-induced destabilization. These results suggest that this region must function in context with other sequence elements created by exon inclusion involved in affecting mRNA stability. In summary, inclusion of an exon that encodes PKCbetaII mRNA introduces a cis-acting region that confers destabilization to the mRNA in response to glucose.

Animals↗

PubMed2003

Missense, nonsense, and neutral mutations define juxtaposed regulatory elements of splicing in cystic fibrosis transmembrane regulator exon 9.

Exonic sequence variations may induce exon inclusion or exclusion from the mature mRNA by disrupting exonic regulatory elements and/or by affecting a nuclear reading frame scanning mechanism. We have carried out a systematic study of the effect on cystic fibrosis transmembrane regulator exon 9 splicing of natural and site-directed sequence mutations. We have observed that changes in the splicing pattern were not related to the creation of premature termination codons, a fact that indicates the lack of a significant nuclear check of the reading frame in this system. In addition, the splice pattern could not be predicted by available Ser/Arg protein matrices score analysis. An extensive site-directed mutagenesis of the 3' portion of the exon has identified two juxtaposed splicing enhancer and silencer elements. The study of double mutants at these regulatory elements showed a complex regulatory activity. For example, one natural mutation (146C) enhances exon inclusion and overrides all of the downstream silencing mutations except for a C to G transversion (155G). This unusual effect is explained by the creation of a specific binding site for the inhibitory splicing factor hnRNPH. In fact, on the double mutant 146C-155G, the silencing effect is dominant. These results indicate a strict dependence between the two juxtaposed enhancer and silencer sequences and show that many point mutations in these elements cause changes in splicing efficiency by different mechanisms.

Alternative Splicing↗

PubMed2004

hnRNP A1 and the SR proteins ASF/SF2 and SC35 have antagonistic functions in splicing of beta-tropomyosin exon 6B.

Mutually exclusive splicing of exons 6A and 6B from the chicken beta-tropomyosin gene involves numerous regulatory sequences. Previously, we identified a G-rich intronic sequence (S3) downstream of exon 6B. This element consists of six G-rich motifs, mutations of which abolish splicing of exon 6B. In this paper, we investigated the cellular factors that bind to this G-rich element. By using RNA affinity chromatography, we identified heterogeneous nuclear ribonucleoprotein (hnRNP) A1, the SR proteins ASF/SF2 and SC35, and hnRNP F/H as specific components that are assembled onto the G-rich element. By using hnRNP A1-depleted HeLa nuclear extract and add-back experiments, we show that hnRNP A1 has a negative effect on splicing of exon 6B. In agreement with in vitro data, artificial recruitment of hnRNP A1, as a fusion with the MS2 coat protein, also represses splicing of exon 6B ex vivo. In contrast, ASF/SF2 and SC35 activate splicing of exon 6B. As observed with other systems, hnRNP A1 counteracts the stimulating effect of the SR proteins. Moreover, cross-linking experiments show that both ASF/SF2 and SC35 are able to displace binding of hnRNP A1 to the G-rich element, suggesting that the binding sites for these proteins are overlapping. These data indicate that the G-rich sequence is a composite element that acts as an enhancer or as a silencer, depending on which proteins bind to them.

Alternative Splicing↗

PubMed1992

Compartmentalization of PDGF on extracellular binding sites dependent on exon-6-encoded sequences.

The PDGFs are a family of molecules assembled as disulfide-bonded homo- and heterodimers from two distinct but highly homologous polypeptide chains (PDGF-A and PDGF-B). Two PDGF A-chain transcripts, which arise from alternative usage of the 69-bp exon 6 and exon 7, give rise to two forms of PDGF-A. In spite of the conservation of two PDGF A-chain forms over at least 350 million years, no differences in their biological activities have been identified. We have investigated the activity of the sequence encoded by the alternatively spliced exon 6 of the PDGF A-chain (peptide AL). Addition of peptide AL at 10(-5)-10(-9) M to cultured endothelium and smooth muscle induced a dose-dependent, 3-20-fold increase in PDGF in conditioned media within 30 min. Peptide AL had no detectable effect on A- or B-chain transcript levels, and decrease in culture temperature did not prevent rapid release of PDGF. In human umbilical vein endothelial cells treated with peptide AL, the PDGF release was principally PDGF-BB, while in smooth muscle cells it was primarily PDGF-AA. The capacity to induce release of PDGF is shared by the homologous peptide encoded by exon 6 of the B-chain of PDGF. Binding studies and cross-linking analysis are consistent with a charge-based association of exon 6 sequences with membrane- and matrix-associated heparan-sulfate proteoglycans. We hypothesize that translation of exon 6 of the A- or B-chain of PDGF results in compartmentalization of these forms of PDGF with HS-PG, whereas forms lacking this sequence would be soluble and diffuse.

Amino Acid Sequence↗

PubMed2004

Chimeric RNA/ethylene-bridged nucleic acids promote dystrophin expression in myocytes of duchenne muscular dystrophy by inducing skipping of the nonsense mutation-encoding exon.

Editing of dystrophin mRNA by induction of exon skipping, using antisense oligonucleotides, has been proposed as one way to generate dystrophin expression in Duchenne muscular dystrophy (DMD) patients. Here, antisense chimeric oligonucleotides consisting of RNA and a new modified nucleic acid are tested for activity to induce skipping of an exon containing a nonsense mutation. In a Japanese DMD case, a nonsense mutation (R1967X) due to a single nucleotide change in exon 41 of the dystrophin gene (C5899T) was identified. Oligonucleotides consisting of 2'-O-methyl RNA and a new 2'-O,4'-C-ethylene-bridged nucleic acid (ENA) were designed to bind the mutation site of exon 41, and their ability to induce exon 41 skipping in dystrophin mRNA was evaluated. Finally, among the specific oligonucleotides tested, an 18-mer RNA/ENA chimera was found to have the strongest activity, inducing exon 41 skipping in nearly 90% of dystrophin mRNA. Accordingly, nearly 90% of cultured myocytes were shown to be dystrophin positive by immunohistochemical analysis. Western blot analysis disclosed the presence of nearly normal-sized dystrophin up to 1 week after the transfection. Our results suggest that an RNA/ENA chimera can be used to express dystrophin in DMD.

Base Sequence↗

PubMed2004

Chimeric RNA and 2'-O, 4'-C-ethylene-bridged nucleic acids have stronger activity than phosphorothioate oligodeoxynucleotides in induction of exon 19 skipping in dystrophin mRNA.

Antisense phosphorothioate oligodeoxynucleotides against exon 19 of the dystrophin gene have been shown to induce exon 19 skipping and promote the expression of internally deleted dystrophin by correcting the translational reading frame. Because phosphorothioate oligonucleotides are associated with a variety of toxic nonantisense effects, several modifications of nucleic acid have been introduced to alleviate this toxicity. Recently, a 2'-O, 4'-C-ethylene-bridged nucleic acid (ENA trade mark, Sankyo Lifetech Co., Ltd., Tokyo, Japan) was reported to have high affinity to complementary RNA strands and be resistant to nuclease digestion. Here, we examined the ability of this modified nucleic acid to induce exon skipping. Oligonucleotides having the same sequence as the phosphorothioate oligonucleotides but with some stretches of modified backbone (2'-O-methyl RNA with an ENA5-mer at the 5'-end and 3'-end) (RNA/ENA chimera) were transfected into myocytes, and the expressed dystrophin mRNA was analyzed. The RNA/ENA chimera induced exon 19 skipping in a dose-dependent and time-dependent manner. Remarkably, the exon 19-skipping activity of the RNA/ENA chimera was more than 40 times stronger than that of the corresponding conventional phosphorothioate oligodeoxynucleotide. This is the first report of such strong activity of an RNA/ENA chimera in the induction of exon skipping in the dystrophin gene. This new technology will allow the development of less toxic antisense drugs, making long-term therapy possible.

Base Sequence↗

PubMed1998

Mouse prolactin receptor gene: genomic organization reveals alternative promoter usage and generation of isoforms via alternative 3'-exon splicing.

In rodents, the prolactin receptor is expressed as multiple isoforms with identical extracellular and membrane-proximal region sequences but with different 3' sequences, encoding different cytoplasmic regions, and different 5' untranslated region (UTR) sequences. These divergent sequences could be the result of multiple prolactin receptor genes or of a single gene which displays alternative promoter usage and 3'-exon splicing. To investigate the molecular basis for these observations, we have cloned and determined the organization of the mouse prolactin receptor gene. Genomic DNA cloning allowed the arrangement of promoters 1A, 1B, and 1C to be determined. 5'-RACE-PCR from mouse liver identified two novel 5' prolactin receptor sequences, indicating that the gene has at least five different promoters, four of which are active in liver. The remaining nonvariable 5' UTR is encoded by a separate exon (exon 2), while a further 11 coding exons follow, the last 4 of which are alternatively spliced to produce the four isoforms of the receptor. Functional units were found to be exon specific. Thus, the multiple prolactin receptor isoforms are the product of a single gene of >120 kb which displays multiple promoter usage and 3'-exon splicing.

Alternative Splicing↗

PubMed1999

Antisense oligodeoxynucleotides targeting internal exon sequences efficiently regulate TNF-alpha expression.

ABSTRACT Exon sequences upstream of splice sites play a critical role in mRNA processing, which is dependent on spliceosome interactions with these sites. Using antisense oligodeoxynucleotides (ODN), we targeted these and other sequences of the proinflammatory tumor necrosis factor-alpha (TNF-alpha) gene because it is multiply spliced and has been difficult to regulate with ODN in the past. ODN targeting exon sequences upstream of the donor splice sites of internal exons 2 (ORF4) and 3 (ORF6) significantly reduced TNF-alpha levels in stimulated U937 cells by 62%+/-7% and 51%+/-9%, respectively, in a dose-dependent manner but did not affect interleukin-6 (IL-6) levels. In contrast, ODN targeting the exon sequences downstream of the acceptor splice sites of exons 1, 2, and 3 failed to reduce TNF-alpha levels significantly under the same conditions. End-phosphorothioated ORF4 (ORF4-PE) significantly reduced TNF-alpha mRNA levels by greater than 80% (p < 0.001) and protein levels by 60% (p < 0.001) in U937 cells. ORF4-PE reduced newly synthesized TNF-alpha protein levels by >80% in lipopolysaccharide (LPS)-stimulated human macrophages, by greater than 60% in phorbol myristate acetate/phyto-hemagglutinin (PMA/PHA)-stimulated human peripheral blood mononuclear cells (PBMC), and by approximately 50% in LPS-stimulated murine monocytes. These results suggest that exon sequences flanking donor splice sites are highly susceptible target domains for antisense inhibition of TNF-alpha gene expression.

Animals↗

PubMed1996

Thyroglobulin exon 10 gene point mutation in a patient with endemic goiter.

Iodine deficiency is the most relevant etiologic factor in endemic goiter. However, the fact that not all residents in the same area eventually develop goiter suggests that individual factors might also be involved in the etiology of endemic goiter. We have previously reported a point mutation in thyroglobulin exon 10 associated with nonendemic simple goiter. In an attempt to determine whether the mutation in thyroglobulin exon 10 might be linked to endemic goiter, we studied the genomic organization of thyroglobulin exon 10 in 36 patients diagnosed with endemic goiter by Southern blot, PCR, and sequencing analysis. We also analyzed by Southern blot the organization of the genomic region that contains thyroglobulin exons 1 to 11. In one case, we observed a point mutation in thyroglobulin exon 10. Sequencing analysis revealed a mutation at position 2610 of the cDNA, which implies a G to T substitution. This single base change results in a glutamine to histidine substitution and is the same as that previously reported by our group in patients with nonendemic goiter. To our knowledge, this is the first time that a mutation in the thyroglobulin gene has been described in a patient with endemic simple goiter and further confirms the association between the exon 10 mutation and development of goiter.

Adult↗

PubMed2005

Assessing the application of Ka/Ks ratio test to alternatively spliced exons.

SUMMARY: Recently, the Ka/Ks ratio test, which assesses the protein-coding potentials of genomic regions based on their non-synonymous to synonymous divergence rates, has been proposed and successfully used in genome annotations of eukaryotes. We systematically performed the Ka/Ks ratio test on 925 transcript-confirmed alternatively spliced exons in the human genome, which we describe in this manuscript. We found that 22.3% of evolutionarily conserved alternatively spliced exons cannot pass the Ka/Ks ratio test, compared with 9.8% for constitutive exons. The false negative rate was the highest (85.7%) for exons with low frequencies of transcript inclusion. Analyses of alternatively spliced exons supported by full-length mRNA sequences yielded similar results, and nearly half of exons involved in ancestral alternative splicing events could not pass this test. Our analysis suggests a future direction to incorporate comparative genomics-based alternative splicing predictions with the Ka/Ks ratio test in higher eukaryotes with extensive RNA alternative splicing.

Algorithms↗

PubMed2001

Nuclear factor TDP-43 and SR proteins promote in vitro and in vivo CFTR exon 9 skipping.

Alternative splicing of human cystic fibrosis transmembrane conductance regulator (CFTR) exon 9 is regulated by a combination of cis-acting elements distributed through the exon and both flanking introns (IVS8 and IVS9). Several studies have identified in the IVS8 intron 3' splice site a regulatory element that is composed of a polymorphic (TG)m(T)n repeated sequence. At present, no cellular factors have been identified that recognize this element. We have identified TDP-43, a nuclear protein not previously described to bind RNA, as the factor binding specifically to the (TG)m sequence. Transient TDP-43 overexpression in Hep3B cells results in an increase in exon 9 skipping. This effect is more pronounced with concomitant overexpression of SR proteins. Antisense inhibition of endogenous TDP-43 expression results in increased inclusion of exon 9, providing a new therapeutic target to correct aberrant splicing of exon 9 in CF patients. The clinical and biological relevance of this finding in vivo is demonstrated by our characterization of a CF patient carrying a TG10T9(DeltaF508)/TG13T3(wt) genotype leading to a disease-causing high proportion of exon 9 skipping.

Alternative Splicing↗

PubMed2002

SR proteins and hnRNP H regulate the splicing of the HIV-1 tev-specific exon 6D.

A naturally arising point mutation in the env gene of HIV-1 activates the aberrant inclusion of the cryptic exon 6D into most viral messages, leading to inefficient viral replication. We set out to understand how a single nucleotide substitution could cause such a dramatic change in splicing. We have determined that the exon 6D mutation promotes binding of the SR protein SC35 to the exon. Mutant exon 6D sequences function as a splicing enhancer when inserted into an enhancer-dependent splicing construct. hnRNP H family proteins bind to the enhancer as well; their binding is dependent on the sequence GGGA located just downstream of the point mutation and depletion-- reconstitution studies show that hnRNP H is essential for enhancer activity. A polypurine sequence located further downstream in exon 6D binds SR proteins but acts as an exonic splicing silencer. hnRNP H is required for interaction of U1 snRNP with the enhancer, independent of the point mutation. We propose that SC35 binding to the point mutation region may convert the hnRNP H-U1 snRNP complex into a splicing enhancer.

Base Sequence↗