Analysis of the role of Caenorhabditis elegans GC-AG introns in regulated splicing.
GC-AG introns represent 0.7% of total human pre-mRNA introns. To study the function of GC-AG introns in splicing regulation, 196 cDNA-confirmed GC-AG introns were identified in Caenorhabditis elegans. These represent 0.6% of the cDNA- confirmed intron data set for this organism. Eleven of these GC-AG introns are involved in alternative splicing. In a comparison of the genomic sequences of homologous genes between C.elegans and Caenorhabditis briggsae for 26 GC-AG introns, the C at the +2 position is conserved in only five of these introns. A system to experimentally test the function of GC-AG introns in alternative splicing was developed. Results from these experiments indicate that the conserved C at the +2 position of the tenth intron of the let-2 gene is essential for developmentally regulated alternative splicing. This C allows the splice donor to function as a very weak splice site that works in balance with an alternative GT splice donor. A weak GT splice donor can functionally replace the GC splice donor and allow for splicing regulation. These results indicate that while the majority of GC-AG introns appear to be constitutively spliced and have no evolutionary constraints to prevent them from being GT-AG introns, a subset of GC-AG introns is involved in alternative splicing and the C at the +2 position of these introns can have an important role in splicing regulation.
Farrer
Tracy
T
Department of MCD Biology and Center for Molecular Biology of RNA, Sinsheimer Laboratories, University of California, Santa Cruz, CA 95064, USA.
Roller
A Brock
AB
Kent
W James
WJ
Zahler
Alan M
AM
D017398:Alternative Splicing; D000818:Animals; D001483:Base Sequence; D017173:Caenorhabditis elegans / Q000235:genetics*; D017124:Conserved Sequence; D017238:Genes, Helminth; D007438:Introns / Q000502:physiology*; D008957:Models, Genetic; D018510:RNA, Helminth / Q000737:chemistry* / Q000378:metabolism*
D018510:RNA, Helminth