Differential distributions of mononucleotide repeat sequences in 256 viral genomes and its potential implications

•We surveyed 256 viral genomes for the presence of mononucleotide repeats (MNRs).•The variation in MNR distribution is influenced by viral genome size and CG content.•MNR frequency and density are lower in genes than in non-coding regions of the genome.•Host range and genome type can affect the relative MNR distribution in viral genomes.•MNRs could potentially be a source of sequence variation for evolutionary adaptation.

Mononucleotide repeats (MNRs) have been systematically investigated in the genomes of eukaryotic and prokaryotic organisms. However, detailed information on the distribution of MNRs in viral genomes is limited. In this study, we examined the distributions of MNRs in 256 fully sequenced virus genomes which showed extensive variations across viral genomes, and is significantly influenced by both genome size and CG content. Furthermore, the ratio of the observed to the expected number of MNRs (O/E ratio) appears to be influenced by both the host range and genome type of a particular virus. Additionally, the densities and frequencies of MNRs in genic regions are lower than in non-coding regions, suggesting that selective pressure acts on viral genomes. We also discuss the potential functional roles that these MNR loci could play in virus genomes. To our knowledge, this is the first analysis focusing on MNRs in viruses, and our study could have potential implications for a deeper understanding of virus genome stability and the co-evolution that occurs between a virus and its host.