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. Highlights • A dataset of 80 pairs of homologous overlapping genes from viruses is examined. • Its analysis reveals that half of overlapping genes undergo asymmetric evolution. • The most variable gene product is that encoded by the de novo overlapping gene. • Overlapping genes evolving asymmetrically are a source of selective protein adaptation.
【저자키워드】 selection pressure, virus adaptation, homologs, Ancestral frame,