THE VARICELLA-ZOSTER VIRUS ORIGIN-BINDING PROTEIN CAN SUBSTITUTE FOR THE HERPES-SIMPLEX VIRUS ORIGIN-BINDING PROTEIN IN A TRANSIENT ORIGIN-DEPENDENT DNA-REPLICATION ASSAY IN INSECT CELLS

We isolated two recombinant baculoviruses each of which expresses a va ricella-zoster virus (VZV) homolog of one of the seven herpes simplex virus type 1 (HSV-1) genes required for DNA replication. We performed transient origin-dependent DNA replication assays in insect cells in w hich we substituted a baculovirus which expresses a VZV protein for a baculovirus which expresses its HSV homolog. VZV gene 51 protein was f ound to be able to support origin-dependent DNA synthesis when it was substituted for UL9, the HSV-1 origin-binding protein (OBP). This occu rred whether an HSV-1 or a VZV origin-containing plasmid was used in t he assay. These results suggest that VN gene 51 protein is able to int eract with the HSV replication machinery, and in light of the extensiv e structural divergence of these proteins, it suggests that initiation of VZV and HSV-1 DNA synthesis may involve a limited number of intera ctions between the OBP and other replication factors. Substitution of infected-cell protein 8 (ICP8), the major single-stranded DNA-binding protein of HSV-1, with VZV gene 29 protein, however, did not result in amplification of plasmids containing either an HSV-1 or a VZV origin. In the absence of ICP8, addition of both VZV gene 51 protein and gene 29 protein was also negative for origin-dependent replication whether or not UL9 was present. Although demonstration that our baculovirus-e xpressed VZV gene 29 protein is functional for DNA replication will aw ait development of a VZV replication system, our results suggest that VZV gene 29 protein is unable to interact functionally with one or mor e of the HSV replication proteins. This approach should contribute to efforts to define the interactions among the alphaherpesvirus DNA repl ication proteins. (C) 1995 Academic Press, Inc.