Herpes simplex virus DNA replication: The UL9 gene encodes an origin-binding protein

Abstract

Herpes simplex virus 1 contains seven genes that are necessary and sufficient for origin-dependent DNA synthesis in cultured cells. We have expressed the product of one of these genes, UL9, in insect cells by using a baculovirus expression vector. The apparent size of the UL9 protein, both in insect cells and in herpes simplex virus-infected Vero cells, is 82,000 Da. By using an immunoassay for protein-DNA interaction, we have shown that UL9 protein binds specifically to the herpes simplex virus origins of DNA replication, ori(S) and ori(L). DNase I 'footprint' analysis has shown that the UL9 protein interacts with two related sites on ori(S), located on each arm of a nearly perfect palindrome. Our data strongly suggest that the origin-binding activity described previously by Elias et al. [Elias, P., O'Donnell, M.E., Mocarski, E.S. and Lehman, I.R. (1986) Proc. Natl. Acad. Sci. USA 83, 6322-6326] is the product of the UL9 gene.