The role of mutational robustness in RNA virus evolution

RNA viruses have extremely high mutation rates that are orders of magnitude greater than those of DNA-based organisms. Although some of these mutations are beneficial, the vast majority are detrimental to fitness.Mutational robustness describes the preservation of phenotype in the face of ongoing mutation. Evolutionary theory suggests that high mutation rates drive the selection of mutational robustness.The relative mutational robustness of an RNA virus can be measured by experiments assessing the accumulation of mutations, the effects of random mutations or mutagen sensitivity.Factors such as a large population size and the ability to infect at high multiplicity can lead to increased robustness.In silico modelling and experimental evolution suggest that viral RNA structures are genotypically diverse but preserve a native fold. Codon usage might also confer mutational robustness at the level of the viral genome.Cellular chaperones might confer mutational robustness to RNA viruses by stabilizing mutant proteins and preventing their misfolding or aggregation.Mutational robustness might favour viral evolvability and increase the ability of a virus to survive in the dynamic host environment. Evolved robustness could complicate efforts to control viral infections through drug-induced increases in the viral mutation rate.