On the stability of sequences inserted into viral genomes

Willemsen, Anouk; Zwart, Mark P

Experimentally it has also been shown that vaccinia virus has a highly plastic genome. After deletion of one host range gene of vaccinia virus, another host range gene increases in copy number (Elde et al. 2012) , leading to genomic expansion. The increased gene expression is in itself beneficial, but the high gene copy number also increases the supply of beneficial gain-offunction mutations. Once these gain-of-function mutations are fixed in the population, the other copies of the gene are lost and thus the vaccinia genome size decreased (associated with the cost of an increased genome size) (Elde et al. 2012 ), leading to accordion-like evolutionary dynamics (Andersson, Slechta, and Roth 1998) .