Partial characterization of two serologically related DNA-binding proteins specified by the cottontail rabbit herpesvirus CTHV.

We have previously described two serologically related DNA-binding phosphoproteins of different apparent molecular mass (75 kDa and 35 kDa) produced in cottontail rabbit herpesvirus (CTHV)-infected cells. The 75 kDa protein appeared before the 35 kDa protein in the infectious cycle. Here, we extend the characterization of these proteins. Protease V8 fingerprints of methionine-labelled 35 kDa protein showed four major peptide products, three of which co-migrated with major peptides from digests of the 75 kDa protein. The fourth peptide, with an estimated mass of 10 kDa, reacted with an antiserum recognizing both proteins. In vitro translation of total or poly A-containing RNA isolated from infected cells at 24 h to 72 h post-infection produced only the 75 kDa protein as measured by immunoprecipitation with anti-75/35 kDa serum, suggesting that the 35 kDa protein is derived from the 75 kDa protein by proteolytic cleavage. Virus-specific RNA obtained by prehybridization to CTHV DNA also produced the 75 kDA protein, confirming its viral origin. The putative gene for the 75 kDa protein was localized to a region on the CTHV DNA restricted by PvuII.