Stop Codon Polymorphism in Two Saccharomyces Species

Abstract

The origin of new coding sequence is a major puzzle in biology. The evolutionary pressures on new sequences are largely unknown, but structural constraints are thought to play a role. Previously, 3' untranslated region (UTR) conversion to open reading frame (ORF) was observed in Saccharomyces. We sought to identify genes that were polymorphic for stop codon position in S. cerevisiae and S. paradoxus. Using strain sequence data from the Saccharomyces Genome Resequencing Project, we found 1336 genes that had evidence of stop codon polymorphism. Of those, we found 62 genes that had evidence of addition to ancestral sequence that represented the conversion of ancestral 3' UTR to derived ORF. Two of these genes, YGL058W and YNL034W-A, are prime candidates for structural studies as they are short proteins with long additions and known structures. In future studies, they will be used to infer any structural constraints on newly evolving proteins.