Base composition changes indicate biased gene conversion is a major factor in the evolution of the Fam53A gene

Abstract

We have conducted a phylogenetic analysis of the Fam53A gene throughout vertebrate evolution. Our studies reveal extreme differences in the rates of change between lineages. In particular, rates of change are much higher in placental mammals (Eutheria) than in other groups. The faster evolutionary rates of change in Eutheria correlate with a transition of the Fam53A‐containing isochore towards a much higher guanosine and cytosine (G+C) content. Changes in isochore G+C content are now thought to reflect changes in regional meiotic recombination rates, and to result from base composition biases in the recombination machinery. We have investigated the recent base composition changes for the Fam53A gene in two eutherian groups, rodents and primates, in which we have dense taxon sampling. Our initial goal in comparing these two groups was to compare the evolution of Fam53A in a clade in which the gene is located close to the telomeres (primates) to one in which the telomeric location has been lost (rodents). While we found that chromosomal location did not correlate with evolutionary changes, our studies indicate that the mapping of historical sequence changes may allow the mapping of ancient recombination hot spots. Sequences within the primate Fam53A genes display localized, transient, increases in G+C content, as would be expected from the known biology of recombination hot spots.