CHARACTERIZATION OF THE UL16 GENE-PRODUCT OF HERPES-SIMPLEX VIRUS TYPE-2

We have raised rabbit polyclonal antisera against a His-tagged herpes simplex virus type 1 (HSV-I) UL16 fusion protein, one of which very sp ecifically reacted with 40 kDa and 41 kDa proteins in the lysates of H SV-1 and HSV-2-infected cells, respectively. Since its reactivity to t he 41 kDa protein was clearly eliminated by pre-adsorption with E. col i lysates expressing the UL16 fusion protein, the antiserum was used t o characterize the UL16 products of HSV-2. The HSV-2 UL16 protein was produced at the late phase of infection in a manner highly dependent o n viral DNA synthesis and was distributed in both the nuclei and the c ytoplasma of infected cells. In immunofluorescence studies, the UL16-s pecific fluorescence in the nuclei was shown to be detected as small d iscrete granules. On the other hand, the cytoplasmic fluorescence was diffusely distributed around the nucleus at 8 h postinfection but, at later times of infection, it was mainly detected as a mass at a perinu clear region. The analysis on its association with capsids has reveale d that the UL16 protein copurified with C capsids but not B and A caps ids, and that the association with C capsids was not tight. Moreover, our experiments have shown that a detectable level of the UL16 protein was not associated with extracellular virions, and that the partially purified UL16 proteins had a DNA-binding activity. These observations are consistent with the hypothesis that the UL16 protein plays a role in capsid maturation including DNA packaging/cleavage. We have also d etermined the complete nucleotide sequence of the HSV-2 UL16 gene and found that a nonstandard initiation codon may be used for its translat ion.