The human DnaJ protein, hTid-1, enhances binding of a multimer of the herpes simplex virus type 1 UL9 protein to oris, an origin of viral DNA replication.

We have identified cellular proteins that interact with the herpes simplex virus type 1 (HSV-1) origin-binding protein (UL9 protein) by screening a HeLa cell complementary DNA library by using the yeast two-hybrid system. Approximately 7 x 10(5) colonies were screened. Five of the 48 positive clones contained cDNAs that encoded the p150(Glued) component of the dynactin complex, three contained cDNAs for the neural F Box 42-kDa protein (NFB42), which is highly enriched in neural tissue, and three contained hTid-1, a human homologue of the bacterial DnaJ protein. We have focused in this report on the interaction of the viral UL9 protein with the cellular hTid-1. In vitro immunoprecipitation experiments confirmed that hTid-1 interacts with the UL9 protein. Electrophoretic mobility-shift assays indicated that the hTid-1 enhances the binding of UL9 protein to an HSV-1 origin, ori(s), and facilitates formation of the multimer from the dimeric UL9 protein. hTid-1 had no effect on the DNA-dependent ATPase or helicase activities associated with the UL9 protein. These findings implicate hTid-1 in HSV-1 DNA replication, and suggest that this cellular protein may provide a chaperone function analogous to the DnaJ protein in Escherichia coli DNA replication.