Search for Genes Positively Selected during Primate Evolution by 5′-End-Sequence Screening of Cynomolgus Monkey cDNAs

Abstract It is possible to assess positive selection by using the ratio of K a (nonsynonymous substitutions per plausible nonsynonymous sites) to K s (synonymous substitutions per plausible synonymous sites). We have searched candidate genes positively selected during primate evolution by using 5′-end sequences of 21,302 clones derived from cynomolgus monkey ( Macaca fascicularis ) brain cDNA libraries. Among these candidates, 10 genes that had not been shown by previous studies to undergo positive selection exhibited a K a / K s ratio > 1. Of the 10 candidate genes we found, 5 were included in the mitochondrial respiratory enzyme complexes, suggesting that these nuclear-encoded genes coevolved with mitochondrial-encoded genes, which have high mutation rates. The products of other candidate genes consisted of a cell-surface protein, a member of the lipocalin family, a nuclear transcription factor, and hypothetical proteins.