Chakraborty Sandip, Alvarez-Ponce David
Department of Biology, University of Nevada, Reno, NV 89557, USA.
Biomed Res Int. 2016;2016:4658506. doi: 10.1155/2016/4658506. Epub 2016 Mar 28.
Proteins within a molecular network are expected to be subject to different selective pressures depending on their relative hierarchical positions. However, it is not obvious what genes within a network should be more likely to evolve under positive selection. On one hand, only mutations at genes with a relatively high degree of control over adaptive phenotypes (such as those encoding highly connected proteins) are expected to be "seen" by natural selection. On the other hand, a high degree of pleiotropy at these genes is expected to hinder adaptation. Previous analyses of the human protein-protein interaction network have shown that genes under long-term, recurrent positive selection (as inferred from interspecific comparisons) tend to act at the periphery of the network. It is unknown, however, whether these trends apply to other organisms. Here, we show that long-term positive selection has preferentially targeted the periphery of the yeast interactome. Conversely, in flies, genes under positive selection encode significantly more connected and central proteins. These observations are not due to covariation of genes' adaptability and centrality with confounding factors. Therefore, the distribution of proteins encoded by genes under recurrent positive selection across protein-protein interaction networks varies from one species to another.
分子网络中的蛋白质预计会因其相对层次位置而受到不同的选择压力。然而，网络中的哪些基因更有可能在正选择下进化并不明显。一方面，只有那些对适应性表型具有相对较高控制程度的基因（例如那些编码高度连接蛋白的基因）发生的突变才有望被自然选择“看到”。另一方面，预计这些基因的高度多效性会阻碍适应性。先前对人类蛋白质-蛋白质相互作用网络的分析表明，长期反复经历正选择的基因（从种间比较推断）往往在网络边缘起作用。然而，这些趋势是否适用于其他生物尚不清楚。在这里，我们表明长期正选择优先针对酵母相互作用组的边缘。相反，在果蝇中，正选择下的基因编码的蛋白连接性和中心性明显更高。这些观察结果并非由于基因的适应性和中心性与混杂因素的共变。因此，反复经历正选择的基因所编码的蛋白质在蛋白质-蛋白质相互作用网络中的分布因物种而异。
