Integration of retroviral DNA into the genome of the infected cell

Retroviruses replicate through an intermediate known as a provirus, a DNA copy of the viral genome that is covalently integrated into the host genome. The formation of the integrated provirus ensures the persistence of the viral genome in the infected cell and its transmission to daughter cells. Integration is thus central to the ability of retroviruses to make permanent genetic changes in the host cell through transfer of active oncogenes or through insertional activation of endogenous proto-oncogenes. Our current understanding of the integration reaction will be reviewed below.