Herpes simplex virus helicase-primase: the UL8 protein is not required for DNA-dependent ATPase and DNA helicase activities.

The herpes simplex virus type 1 helicase-primase complex consists of the products of the UL5, UL8 and UL52 genes. We have expressed these proteins in insect cells using baculovirus vectors and studied the requirements for enzymatic activities associated with the DNA unwinding function of the complex. In agreement with a recent report (Dodson, M.S., Crute, J.J., Bruckner, R.C. and Lehman, I.R. 1989, J. Biol. Chem. 264, 20835-20838) we find that DNA-dependent ATPase and DNA helicase activities are assembled in vivo in insect cells triply infected with viruses expressing the UL5, UL8 and UL52 proteins. Moreover, these activities were also detected in cells in which only the UL5 and UL52 products were expressed indicating that the presence of the UL8 protein is essential for neither the ATPase nor helicase activity of the complex.