Identification of a Virus-specified Protein in the Nucleus of Vaccinia Virus-infected Cells

Abstract

A new protein has been detected in the nuclei of vaccinia virus-infected cells. This protein has an apparent mol. wt. of 28000 (VP28) on SDS-polyacrylamide gels and has been detected in Triton X-100-treated nuclei of infected BSC-40, L-929 and CVC cells. Within the infected cells, VP28 was synthesized maximally at 1 to 2 h p.i. in the cytoplasm and accumulated in the nuclei at 4 to 5 h p.i. The appearance of VP28 was not affected by cytosine arabinoside (25 µg/ml), an inhibitor of virus DNA synthesis, or rifampicin (100 µg/ml), an inhibitor of vaccinia assembly, but was inhibited by irradiation of the infecting virions; thus classifying it as an early vaccinia virus gene product. Nuclear-cytoplasmic mixing experiments suggested that the nuclear location of VP28 was not an artefact of the cell fractionation techniques employed. VP28 did not appear to be phosphorylated.