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 a n infected cell are less clear. For example, certain chromosomal regio ns may be inaccessible to the viral integration machinery, while other s may favor integration. A recent paper by Withers-Ward et al.((1)) ad dresses this issue using a polymerase chain reaction-based assay capab le 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 i nfluence the site of integration within a given region.