Genome instability in DNA viruses

Abstract

Genome instability generally refers to the appearance of a high frequency of mutations in a genome, including point mutations, insertion/deletions, and large genetic rearrangements. DNA viruses, particularly those with large genomes, show higher genome stability than RNA viruses. However, DNA viruses can also exhibit rapid sequence changes, and some are capable of promoting genome instability specifically at certain regions, such as genes involved in rapidly-changing virus-host interactions. Targeting mutations to defined genome regions allows DNA viruses to boost the production of diversity wherein needed, while avoiding mutational load inflation. We review some of the molecular mechanisms underlying genome instability in bacteriophages and eukaryotic DNA viruses. These include diversity-generating retro-elements, recombination-driven gene amplification, and editing by host-encoded deaminases. We also discuss the interplays between DNA viruses and host post-replicative repair pathways, and their potential implications for viral genome instability.