title: The flatworm spliced leader 3'-terminal AUG as a translation initiator methionine.
abstract: Spliced leader (SL) RNA trans-splicing contributes the 5' termini to mRNAs in a variety of eukaryotes. In contrast with some transsplicing metazoan groups (e.g. nematodes), flatworm spliced leaders are variable in both sequence and length in different flatworm taxa. However, an absolutely conserved and unique feature of all flatworm spliced leaders is the presence of a 3'-terminal AUG. We previously suggested that the Schistosoma mansoni spliced leader AUG might contribute a required translation initiator methionine to recipient mRNAs. Here we identified and examined trans-spliced cDNAs from a large set of newly available schistosome cDNAs. 28% of the trans-spliced cDNAs have the SL AUG in-frame with the major open reading frame of the mRNA. We identified over 40 cDNAs (40% of the SL AUG in-frame clones) that require the SL AUG as an initiator methionine to synthesize phylogenetically conserved N-terminal residues characteristic of orthologous proteins. RNA transfection experiments using several schistosome stages demonstrated that the flatworm SL AUG can serve as a translation initiator methionine in vivo. We also present in vivo translation studies of the schistosome initiator methionine context and the effect of the spliced leader AUG added upstream and out-of-frame with the main open reading of recipient mRNAs. Overall, our data have provided evidence that another function of flatworm spliced leader trans-splicing is to provide some recipient mRNAs with an initiator methionine for translation initiation.
authors.affiliation: Department of Pediatrics, University of Colorado School of Medicine, Aurora, 80045, USA.
authors.forename: Guofeng
authors.initials: G
authors.lastname: Cheng
authors.forename: Leah
authors.initials: L
authors.lastname: Cohen
authors.forename: David
authors.initials: D
authors.lastname: Ndegwa
authors.forename: Richard E
authors.initials: RE
authors.lastname: Davis
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003062:Codon; D019295:Computational Biology; D018076:DNA, Complementary / Q000378:metabolism; D020224:Expressed Sequence Tags; D048888:Fireflies; D017930:Genes, Reporter; D008156:Luciferases / Q000378:metabolism; D008715:Methionine / Q000737:chemistry*; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010802:Phylogeny; D014176:Protein Biosynthesis; D017434:Protein Structure, Tertiary; D012313:RNA / Q000737:chemistry; D012326:RNA Splicing; D012333:RNA, Messenger / Q000378:metabolism; D020038:RNA, Spliced Leader; D012550:Schistosoma mansoni / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D014162:Transfection
chemical_list: D003062:Codon; D018076:DNA, Complementary; D012333:RNA, Messenger; D020038:RNA, Spliced Leader; D012313:RNA; D008715:Methionine; D008156:Luciferases