Fig. 1.

Ancient and variable positive selection has shaped TRIM5α evolution. (A) TRIM5α is the longest of six reported transcripts of the eight-exon human TRIM5 gene. It encodes a 493-aa protein consisting of a RING finger, a B-Box2, and a coiled-coil domain (signature domains of the TRIM family; ref. 24), as well as an α-isoform-specific SPRY domain. (B) TRIM5α was sequenced from a panel of primates representing 33 million years of evolutionary divergence. Values of dN/dS along each branch were calculated by using the free-ratio model of paml for either the whole gene or for the SPRY domain alone (in parentheses), as shown on a cladogram of the accepted primate phylogeny (38). A dN/dS value of >1 suggests that positive selection has acted along that lineage. inf refers to cases where dS = 0.