Multiple Splicing Defects in an Intronic False Exon

AUTOR(ES)

Sun, Hanzhen

FONTE

American Society for Microbiology

RESUMO

Splice site consensus sequences alone are insufficient to dictate the recognition of real constitutive splice sites within the typically large transcripts of higher eukaryotes, and large numbers of pseudoexons flanked by pseudosplice sites with good matches to the consensus sequences can be easily designated. In an attempt to identify elements that prevent pseudoexon splicing, we have systematically altered known splicing signals, as well as immediately adjacent flanking sequences, of an arbitrarily chosen pseudoexon from intron 1 of the human hprt gene. The substitution of a 5′ splice site that perfectly matches the 5′ consensus combined with mutation to match the CAG/G sequence of the 3′ consensus failed to get this model pseudoexon included as the central exon in a dhfr minigene context. Provision of a real 3′ splice site and a consensus 5′ splice site and removal of an upstream inhibitory sequence were necessary and sufficient to confer splicing on the pseudoexon. This activated context also supported the splicing of a second pseudoexon sequence containing no apparent enhancer. Thus, both the 5′ splice site sequence and the polypyrimidine tract of the pseudoexon are defective despite their good agreement with the consensus. On the other hand, the pseudoexon body did not exert a negative influence on splicing. The introduction into the pseudoexon of a sequence selected for binding to ASF/SF2 or its replacement with β-globin exon 2 only partially reversed the effect of the upstream negative element and the defective polypyrimidine tract. These results support the idea that exon-bridging enhancers are not a prerequisite for constitutive exon definition and suggest that intrinsically defective splice sites and negative elements play important roles in distinguishing the real splicing signal from the vast number of false splicing signals.

Documentos Relacionados

• Multiple features contribute to efficient constitutive splicing of an unusually large exon
• Do intronic mutations affecting splicing of WT1 exon 9 cause Frasier syndrome?
• An Intronic Splicing Silencer Causes Skipping of the IIIb Exon of Fibroblast Growth Factor Receptor 2 through Involvement of Polypyrimidine Tract Binding Protein
• hnRNP A1 Recruited to an Exon In Vivo Can Function as an Exon Splicing Silencer
• A complex intronic splicing enhancer from the c-src pre-mRNA activates inclusion of a heterologous exon.