The two helicases of herpes simplex virus type 1 (HSV-1).

Herpes simplex virus type 1 (HSV-1) encodes two helicases both of which are essential for viral DNA synthesis. UL9 binds specifically to the origins of replication and is believed to initiate DNA replication at one of three origins of replication located in the HSV-1 genome. The heterotrimeric helicase-primase complex, encoded by the UL5, UL8 and UL52 genes, is believed to unwind duplex viral DNA at replication forks and to prime lagging strand synthesis. Functional analyses of UL9 and the helicase-primase complex will be discussed with attention to the roles these proteins play during HSV-1 replication.