Abstract
BackgroundGene duplications are a source of new genes and protein functions. The innovative role of duplication events makes families of paralogous genes an interesting target for studies in evolutionary biology. Here we study global trends in the evolution of human genes that resulted from recent duplications.ResultsThe pressure of negative selection is weaker during a short time immediately after a duplication event. Roughly one fifth of genes in paralogous gene families are evolving asymmetrically: one of the proteins encoded by two closest paralogs accumulates amino acid substitutions significantly faster than its partner. This asymmetry cannot be explained by differences in gene expression levels. In asymmetric gene pairs the number of deleterious mutations is increased in one copy, while decreased in the other copy as compared to genes constituting non-asymmetrically evolving pairs. The asymmetry in the rate of synonymous substitutions is much weaker and not significant.ConclusionsThe increase of negative selection pressure over time after a duplication event seems to be a major trend in the evolution of human paralogous gene families. The observed asymmetry in the evolution of paralogous genes shows that in many cases one of two gene copies remains practically unchanged, while the other accumulates functional mutations. This supports the hypothesis that slowly evolving gene copies preserve their original functions, while fast evolving copies obtain new specificities or functions.ReviewersThis article was reviewed by Dr. Igor Rogozin (nominated by Dr. Arcady Mushegian), Dr. Fyodor Kondrashov, and Dr. Sergei Maslov.
Highlights
Gene duplications are a source of new genes and protein functions
We report that 18% of recent human paralogous pairs evolve with significant asymmetry and that faster evolving gene copies accumulate functional mutations at a significantly higher proportion slowly evolving genes from the same pairs or genes from nonasymmetrically evolving pairs
Asymmetry at synonymous sites We identified nine pairs of paralogous genes asymmetric according to the number of synonymous substitutions (P < 0.05)
Summary
The innovative role of duplication events makes families of paralogous genes an interesting target for studies in evolutionary biology. We study global trends in the evolution of human genes that resulted from recent duplications. Evolutionary histories of multigene families have been studied in a variety of organisms on the scale of individual families [3,4,5,6,7] as well as in genome-wide analyses [8,9,10,11,12]. Regarding gene duplication and evolution, one of the best studied organisms is the budding yeast S. cerevisiae. This organism experienced a recent whole-genome duplication event [13] that, together with smaller segment duplications provided material for comparison of duplicated genes of different origin.
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