Essential component of the helicase/primase complex. Unwinds the DNA at the replication forks and generates single-stranded DNA for both leading and lagging strand synthesis. The primase initiates primer synthesis and thereby produces large amount of short RNA primers on the lagging strand that the polymerase elongates using dNTPs. Associates with the helicase and the primase-associated factor to form the helicase-primase factor. Requires the presence of the primase associated factor to properly localize in the host cell nucleus. Belongs to the herpesviridae DNA primase family. It is uncertain whether Met-1 or Met-5 is the initiator.