title: The role of evolutionarily conserved sequences in alternative splicing at the 3' end of Drosophila melanogaster myosin heavy chain RNA.
abstract: Exon 18 of the muscle myosin heavy chain gene (Mhc) of Drosophila melanogaster is excluded from larval transcripts but included in most adult transcripts. To identify cis-acting elements regulating this alternative RNA splicing, we sequenced the 3' end of Mhc from the distantly related species D. virilis. Three noncoding regions are conserved: (1) the nonconsensus splice junctions at either end of exon 18; (2) exon 18 itself; and (3) a 30-nucleotide, pyrimidine-rich sequence located about 40 nt upstream of the 3' splice site of exon 18. We generated transgenic flies expressing Mhc mini-genes designed to test the function of these regions. Improvement of both splice sites of adult-specific exon 18 toward the consensus sequence switches the splicing pattern to include exon 18 in all larval transcripts. Thus nonconsensus splice junctions are critical to stage-specific exclusion of this exon. Deletion of nearly all of exon 18 does not affect stage-specific utilization. However, splicing of transcripts lacking the conserved pyrimidine sequence is severely disrupted in adults. Disruption is not rescued by insertion of a different polypyrimidine tract, suggesting that the conserved pyrimidine-rich sequence interacts with tissue-specific splicing factors to activate utilization of the poor splice sites of exon 18 in adult muscle.
authors.affiliation: Biology Department and Molecular Biology Institute, San Diego State University, San Diego, California 92182-4614, USA.
authors.forename: D
authors.initials: D
authors.lastname: Hodges
authors.forename: R M
authors.initials: RM
authors.lastname: Cripps
authors.forename: M E
authors.initials: ME
authors.lastname: O'Connor
authors.forename: S I
authors.initials: SI
authors.lastname: Bernstein
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017124:Conserved Sequence; D018076:DNA, Complementary; D004330:Drosophila / Q000235:genetics; D004331:Drosophila melanogaster / Q000235:genetics*; D019143:Evolution, Molecular; D005091:Exons; D005786:Gene Expression Regulation; D017344:Genes, Insect; D007438:Introns; D007814:Larva; D008969:Molecular Sequence Data; D018995:Myosin Heavy Chains / Q000235:genetics*; D011743:Pyrimidines; D012313:RNA
chemical_list: D018076:DNA, Complementary; D011743:Pyrimidines; D012313:RNA; D018995:Myosin Heavy Chains