On the stability of sequences inserted into viral genomes

Willemsen, Anouk; Zwart, Mark P

At its core, the stability of genomic insertions in viral genomes depends on two key factors. First, the supply of mutations removing the insertion is crucial, because selection can only act on existing heritable variation. Second, selection then acts to fix variants with the inserted sequence removed. All other things equal, the larger the supply of mutations that remove the insertion and the larger the selection coefficients of variants with the insert removed, the less stable the insertion will be. The interplay between mutation and selection will govern the stability of genomic inserts, and in many cases demography has an important role in shaping this interplay. For example, low fitness can lead to small population sizes, which in turn will limit the mutation supply (Chao 1990; Lynch and Gabriel 1990) . A high-cost inserted sequence might therefore limit viral evolvability, thereby promoting its own stability.