PHOSPHORYLATION AND NUCLEAR-LOCALIZATION OF THE VARICELLA-ZOSTER VIRUS GENE-63 PROTEIN

The protein encoded by varicella zoster virus open reading frame 63 an d carboxy-terminal deletions of the same were expressed either as fusi on proteins at the carboxy terminus of the maltose-binding protein in Escherichia coli or independently in transfected mammalian cells. The truncations contained amino acids 1 to 142 (63 Delta N) or 1 to 210 (6 3 Delta K) of the complete 278-amino-acid primary sequence, Recombinan t casein kinase II phosphorylated the 63F and 63 Delta KF fusion prote ins in vitro but did not phosphorylate the 63 Delta NF fusion protein, implying that phosphorylation occurred between amino acids 142 and 21 0. Immunoprecipitation of S-35- or P-32-labelled extracts of cells tra nsfected with plasmids expressing 63, 63 Delta N, or 63 Delta K also i ndicated that in situ phosphorylation most likely occurred between ami no acids 142 and 210. These combined results suggest that casein kinas e II plays a significant role in the phosphorylation of the varicella- zoster virus 63 protein. Indirect immunofluorescence of transfected ce lls indicated nuclear localization of the 63 protein and cytoplasmic l ocalization of 63 Delta K and 63 Delta N, implying a requirement for s equences between amino acids 210 and 278 for efficient nuclear localiz ation.