A FUNCTIONAL INTERACTION OF ICP8, THE HERPES-SIMPLEX VIRUS SINGLE-STRANDED DNA-BINDING PROTEIN, AND THE HELICASE-PRIMASE COMPLEX THAT IS DEPENDENT ON THE PRESENCE OF THE UL8 SUBUNIT

The herpes simplex virus type 1 (HSV) single-stranded DNA-binding prot ein (SSB, ICP8) stimulates the viral DNA polymerase (Pol) on an oligon ucleotide-primed single-stranded DNA template, This stimulation is non -specific since other SSBs also increase Pol activity. However, only I CP8 was stimulatory when Pol activity was dependent upon priming by th e viral helicase-primase complex. ICP8 also specifically stimulated th e primer synthesis and ATPase activities of the helicase-primase, The mechanism of stimulation was different from that of Pol; helicase-prim ase stimulation required much lower amounts of ICP8 than the amount th at saturates the DNA and optimally stimulates Pol. Furthermore, ICP8 d id not act by removing secondary structure as stimulation also occurre d on homopolymer templates. While the UL8 component of the helicase-pr imase is not required for enzymatic activities by a subassembly of the UL5 and UL52 proteins, only the holoenzyme (UL5/8/52) was stimulated by ICP8. These results identify a unique, functional interaction betwe en the ICP8 SSB and the helicase-primase complex, mediated by the UL8 subunit.