Biosynthesis and post-translational cleavage of vaccinia virus structural protein VP8

We have obtained antiserum against highly purified vaccinia virus structural protein VP8, a major DNA binding protein present in the viral core particle. The antiserum has been used to monitor the course of the biosynthesis of this protein. The protein can first be detected in extracts of infected cells at 4 hr postinfection (p.i.). Its synthesis increases significantly at 5 hr p.i. and is maintained at about the same level up to 11 hr. The requirement of viral DNA replication for VP8 synthesis indicates that it is a viral late protein. This protein is synthesized in the form of a 28-kDa precursor, which is then processed to a 25-kDa product. The half-life of the precursor is about 2 hr. Comparing the N-terminal amino acid sequence of this purified protein with those derived from the published DNA sequence of the vaccinia viral genome [J.P. Weir and B. Moss (1984) J. Virol. 51, 662-669], it is found that VP8 maps to the HindIII L fragment of the viral genome. The cleavage site at which processing takes place lies between amino acids 32 (Gly) and 33 (Ala) from the N-terminal end of the precursor.