Fig. 1.

Mechanism of retroviral DNA integration. A multimer of integrase (light orange) engages the ends of linear viral DNA (black lines), synapsing them together within the intasome complex. Integrase 3′ processing activity yields chemically reactive 3′-hydroxyl groups at the viral DNA ends. Following the binding of host DNA (blue lines) in the nucleus, integrase promotes the strand transfer or DNA joining reaction (staggered cut site in red). Repair of the DNA recombination intermediate yields a short duplication of host DNA (red lines) flanking the integrated provirus