Purifying selection against gene conversions in the folate receptor genes of primates

We characterized the gene conversions between the human folate receptor (FOLR) genes and those of five other primate species. We found 26 gene conversions having an average length of 534 nucleotides. The length of these conversions is correlated with sequence similarity, converted regions have a higher GC-content and the average size of converted regions from a functional donor to another functional donor is significantly smaller than the average size from a functional donor to a pseudogene. Furthermore, the few conversions observed in the FOLR1 and FOLR2 genes did not change any amino acids in their coding regions and did not affect their promoter regions. In contrast, the promoter and coding regions of the FOLR3 gene are frequently converted and these conversions changed many amino acids in marmoset. These results suggest that purifying selection is limiting the functional impact that frequent gene conversions have on functional folate receptor genes.