M. V. Lomonosov Moscow State University, Faculty of Bioengineering and Bioinformatics, Vorobyevy Gory 1-73, Moscow, 119992, Russia.
Biol Direct. 2010 Sep 8;5:54. doi: 10.1186/1745-6150-5-54.
Gene 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.
The 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.
The 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.
基因重复是新基因和蛋白质功能的来源。重复事件的创新性作用使得同源基因家族成为进化生物学研究的有趣目标。在这里，我们研究了由于最近的重复而导致的人类基因进化的全球趋势。
在重复事件发生后的短时间内，负选择压力较弱。大约五分之一的同源基因家族中的基因在进化上是不对称的：两个最接近的同源基因之一编码的蛋白质比其伴侣积累氨基酸替换的速度明显更快。这种不对称性不能用基因表达水平的差异来解释。在不对称的基因对中，一个拷贝中的有害突变数量增加，而另一个拷贝中的有害突变数量减少，与构成非对称进化对的基因相比。同义替换率的不对称性要弱得多，且不显著。
重复事件后随着时间的推移，负选择压力的增加似乎是人类同源基因家族进化的一个主要趋势。观察到的同源基因进化中的不对称性表明，在许多情况下，两个基因拷贝中的一个保持实际上不变，而另一个则积累功能突变。这支持了这样一种假说，即缓慢进化的基因拷贝保留了它们的原始功能，而快速进化的拷贝获得了新的特异性或功能。
