A TRUNCATED HERPES-SIMPLEX VIRUS ORIGIN-BINDING PROTEIN WHICH CONTAINS THE CARBOXYL-TERMINAL ORIGIN-BINDING DOMAIN BINDS TO THE ORIGIN OF REPLICATION BUT DOES NOT ALTER ITS CONFORMATION

We have studied the DNA binding properties of a polypeptide consisting of the carboxyl terminal 37% of UL9, the herpes simplex virus type 1 (HSV-1) origin of replication binding protein. Using a Sindbis virus e xpression system, we expressed and partially purified this truncated f orm of UL9 (UL9CT) which contains the site-specific DNA binding domain . UL9CT specifically recognized UL9 binding sites on a 200 base pair D NA fragment containing the HSV origin ori(s) and appeared to bind as a dimer to each site. DNAse I footprint analysis showed that UL9CT prot ected the two high affinity binding sites of oris, but unlike full-len gth UL9, UL9CT did not induce a conformational change in the origin. A ddition of anti-UL9CT antibody to the UL9CT-origin complex, however, c aused a conformational change in the origin to be evident. Our results suggest that a domain, or domains, in the amino terminus are necessar y for a UL9-induced origin conformational change to occur and that UL9 -UL9 interactions between binding sites are involved.