Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parco Area delle Scienze 11/A, I-43124, Parma, Italy.
Virology. 2019 Jun;532:39-47. doi: 10.1016/j.virol.2019.03.017. Epub 2019 Apr 3.
Overlapping genes represent an intriguing puzzle, as they encode two proteins whose ability to evolve is constrained by each other. Overlapping genes can undergo "symmetric evolution" (similar selection pressures on the two proteins) or "asymmetric evolution" (significantly different selection pressures on the two proteins). By sequence analysis of 75 pairs of homologous viral overlapping genes, I evaluated their accordance with one or the other model. Analysis of nucleotide and amino acid sequences revealed that half of overlaps undergo asymmetric evolution, as the protein from one frame shows a number of substitutions significantly higher than that of the protein from the other frame. Interestingly, the most variable protein (often known to interact with the host proteins) appeared to be encoded by the de novo frame in all cases examined. These findings suggest that overlapping genes, besides to increase the coding ability of viruses, are also a source of selective protein adaptation.
重叠基因是一个有趣的谜，因为它们编码两种蛋白质，其进化能力受到彼此的限制。重叠基因可以经历“对称进化”（两种蛋白质受到相似的选择压力）或“非对称进化”（两种蛋白质受到显著不同的选择压力）。通过对 75 对同源病毒重叠基因的序列分析，我评估了它们符合一种或另一种模型的情况。核苷酸和氨基酸序列分析表明，一半的重叠基因经历了非对称进化，因为一个框架中的蛋白质显示出的替换数量明显高于另一个框架中的蛋白质。有趣的是，在所检查的所有情况下，最具变异性的蛋白质（通常被认为与宿主蛋白相互作用）似乎都是由从头框架编码的。这些发现表明，重叠基因除了增加病毒的编码能力外，还是选择性蛋白质适应的来源。
