DIFFERENCES IN THE INTRACELLULAR-LOCALIZATION AND FATE OF HERPES-SIMPLEX VIRUS TEGUMENT PROTEINS EARLY IN THE INFECTION OF VERO CELLS

The fate of herpes simplex virus 1 (HSV-1) tegument proteins during in fection in Vero cells was investigated immunochemically, Input virion- associated VP13/14 and VP 16 localized to the nucleus early in infecti on, while VP1/2 localized to the nuclear envelope of the cell and VP22 could not be detected using monoclonal antibody P43, Western blotting suggested that virion-associated VP13/14, VP16 and VP22 were stable i n infected cells whereas VP1/2 appeared to be processed or modified. F urther studies showed that P43 recognized a phosphorylation-sensitive epitope in VP22 and suggested that virion-associated VP22 was phosphor ylated upon entry to the cell. VP13/14 and VP16 were easily extracted from cells early in infection whereas VP22 was largely insoluble. Phos phatase treatment of soluble extracts caused a shift in the molecular mass of VP16 showing it was phosphorylated, As infection progressed VP 16 was observed in discrete nuclear compartments where it co-localized with ICPS and the capsid-associated protein VP22a. VP13114 was also o bserved in the nucleus. P43 immunostaining appeared around 6 h post-in fection as punctate nuclear foci which often localized to the edge of VP16-immunoreactive areas. Punctate P43 cytoplasmic staining appeared around 12 h post-infection. By 18 h the nuclear pattern had disappeare d and an extensive cytoplasmic stain was observed which closely overla pped that of other tegument proteins. On the basis of these data we su ggest that virion-associated VP22 is phosphorylated upon entry of the virus into the cell and that unphosphorylated VP22, which is preferent ially recognized by P43, becomes available later in infection, initial ly in the nucleus, for packaging into virions.