U4 small nuclear RNA can function in both the major and minor spliceosomes
Abstract
U4 small nuclear RNA (snRNA) and U6 snRNA form a base-paired di-snRNP complex that is essential for pre-mRNA splicing of the major class of metazoan nuclear introns. The functionally analogous but highly diverged U4atac and U6atac snRNAs form a similar complex that is involved in splicing of the minor class of introns. Previous results with mutants of U6atac in which a substructure was replaced by the analogous structure from U6 snRNA suggested that wild-type U4 snRNA might be able to interact productively with the mutant U6atac snRNA. Here we show that a mutant U4 snRNA designed to base pair with a mutant U6atac snRNA can activate U12-dependent splicing when coexpressed in an in vivo genetic suppression assay. This genetic interaction could also be demonstrated in an in vitro crosslinking assay. These results show that a U4/U6atac di-snRNP can correctly splice a U12-dependent intron and suggest that the specificity for spliceosome type resides in the U6 and U6atac small nuclear ribonucleoproteins. Further experiments suggest that expression of a mutant U4 snRNA that can bind to wild-type U6atac snRNA alters the specificity of some splice sites, providing an evolutionary rationale for maintaining two U4-like snRNAs.
- Publication:
-
Proceedings of the National Academy of Science
- Pub Date:
- January 2004
- DOI:
- 10.1073/pnas.0304919101
- Bibcode:
- 2004PNAS..101...93S
- Keywords:
-
- BIOCHEMISTRY