Book of Abstracts: Albany 2011
June 14-18 2011
©Adenine Press (2010)
Recently Duplicated Human Genes: Basics of Evolution
Gene duplications are one of the major sources of new protein functions. We studied the evolution of recently duplicated human genes. A genome-wide procedure was used to find paralogous genes retaining detectable sequence similarity throughout most exons and introns. Similar genes were collected in families. Only families containing three or more genes were analyzed.
A novel method was introduced for calculating the evolutionary rates of individual genes from such families. It shows that negative selection, acting at a duplicated gene and measured by the Kn/Ks test, is relatively weaker immediately after the duplication event and then increases. Such changes of the negative selection pressure seem to be a major trend in the evolution of young human paralogs.
Another trend concerns the asymmetry of the evolution of two gene copies resulting from a recent duplication event. In about one fifth of recently duplicated gene pairs from young paralogous gene families, the two gene copies accumulate amino acid substitutions at significantly different rates. Differences in the gene expression levels do not explain this asymmetry. The asymmetry in the rate of accumulation of synonymous substitutions is much weaker and not significant. In asymmetric gene pairs the number of deleterious mutations is higher in one copy, and lower in the other copy as compared to genes comprising non-asymmetrically evolving pairs. A possible explanation for this trend is the need for one of the two duplicated gene copies to retain its initial function, as the other copy rapidly evolves to get a new function.
We also compared the evolutionary rates for the original and derived copies of recently duplicated paralogous genes. For primate-specific duplications it is possible to distinguish the original copy based on conservation of the gene neighborhood in rodents, although this can be done reliable only for a minor fraction of genes produced by non-tandem duplications. The Kn values and the Kn/Ks ratios were significantly lower for the original copies compared to the derived ones. Both original and derived copies were evolving under negative selection.
This work is partially supported by the Russian Academy of Sciences (programs “Molecular and Cellular Biology” and “Biodiversity”) and the state contract P1376.
Alexander Y. Panchin2, 3
1Vavilov Institute of General Genetics RAS