title: Selection on Position of Nonsense Codons in Introns.
abstract: Introns occasionally remain in mature messenger RNAs (mRNAs) due to splicing errors and the translated, aberrant proteins that result represent a metabolic cost and may have other deleterious consequences. The nonsense-mediated decay (NMD) pathway degrades aberrant mRNAs, which it recognizes by the presence of an in-frame premature termination codon (PTC). We investigated whether selection has shaped the location of PTCs in introns to reduce waste and facilitate NMD. We found across seven model organisms, that in both first and last introns, PTCs occur earlier in introns than expected by chance, suggesting that selection favors earlier position. This pattern is more pronounced in species with larger effective population sizes. The pattern does not hold for last introns in the two mammal species, however, perhaps because in these species NMD is not initiated from 3'-terminal introns. We conclude that there is compelling evidence that the location of PTCs is shaped by selection for reduced waste and efficient degradation of aberrant mRNAs.
authors.affiliation: Department of Genetics, University of Georgia, Athens, Georgia 30602 megbehri@indiana.edu.
authors.forename: Megan G
authors.initials: MG
authors.lastname: Behringer
authors.affiliation: Department of Genetics, University of Georgia, Athens, Georgia 30602.
authors.forename: David W
authors.initials: DW
authors.lastname: Hall
mesh_terms: D000818:Animals; D017360:Arabidopsis / Q000235:genetics; D017173:Caenorhabditis elegans / Q000235:genetics; D018389:Codon, Nonsense / Q000235:genetics*; D004331:Drosophila melanogaster / Q000235:genetics; D019143:Evolution, Molecular; D006801:Humans; D007438:Introns; D051379:Mice; D059645:Mutation Rate; D059365:Nonsense Mediated mRNA Decay; D012641:Selection, Genetic; D015003:Yeasts / Q000235:genetics
chemical_list: D018389:Codon, Nonsense
keywords: intron definition; nonsense-mediated decay; premature termination codon; splicing errors; translation