Plays an essential role in the initiation of viral DNA synthesis. Binds specifically to an inverted terminal repeat element (ITR) on the 3' and 5' ends of the viral DNA, where it cleaves a site specifically to generate a priming site for initiation of the synthesis of a complementary strand. Also plays a role as transcriptional regulator, DNA helicase and as key factor in site-specific integration of the viral genome. Inhibits the host cell cycle G1/S and G2/M transitions. These arrests may provide essential cellular factors for viral DNA replication. ATP + H2O = ADP + H(+) + phosphate Interacts with host TOPORS. Interacts with host KCTD5.