Most of the avian genome appears available for retroviral DNA integration

Although retroviral integration requires specific viral DNA sequences, factors which govern the choice of a chromosomal target site within an infected celi are less clear. For example, certain chromosomal regions may be inaccessible to the viral integration machinery, while others may favor integration. A recent paper by Withers‐Ward et al. (1) addresses this issue using a polymerase chain reaction‐based assay capable of identifying single integration events within a large population of infected cells. Their results show that integration can occur into many different chromosomal regions, and that local DNA structure can influence the site of integration within a given region.