PHOSPHORYLATION OF THE HERPES-SIMPLEX VIRUS TYPE-I TEGUMENT PROTEIN VP22

The herpes simplex virus type 1 tegument protein VP22 is known to be h ighly phosphorylated during infection. Here we show that two electroph oretic forms of VP22 can be identified in infected cell extracts and t hat this heterogeneity is accounted for by phosphorylation. Furthermor e, the nonphosphorylated form of VP22 appears to be specifically incor porated into virions. We also show that the phosphorylated form of VP2 2 is the only farm detected during transient transfection and as such that VP22 can act as a substrate for a cellular kinase. Phospho-amino acid and phospho-peptide analyses of in vivo labeled VP22 were utilize d to demonstrate that the phosphorylation profiles of VP22 synthesized during transfection and infection are the same. In both cases VP22 wa s modified solely on serine residues located in the N-terminal 120 res idues of the protein. Moreover, in vitro phosphorylation was utilized to show that the constitutive cellular kinase, casein kinase II, which has four serine consensus recognition sites at the N-terminus of VP22 , phosphorylates VP22 in the same manner as observed in vivo. This kin ase also phosphorylates VP22 at the N-terminus in intact capsid-tegume nt structures. Casein kinase II is therefore likely to be the major ki nase of VP22 during infection. (C) 1996 Academic Press, Inc.