Occurrence of bovine herpesvirus-1 DNA in nucleosomes and chromatin of bovine herpesvirus-1-infected cells: identification of a virion-associated protein in chromatin of infected cells.

During virus replication a fraction of the intranuclear DNA of bovine herpesvirus-1 (BHV-1) was present in the nucleosomal structure of infected eukaryotic cells, and virion proteins were associated with the chromatin of virus infected cells. Synthesis of BHV-1 DNA in bovine embryonic lung (BEL) cells was found to begin four to six hours post-infection (p.i.) and to continue until at least 24 hours p.i. Chromatin isolated from infected cell nuclei at ten hours p.i. contained both BHV-1 viral and cell DNA. No BHV-1 DNA was found in mock-infected cell chromatin. Micrococcal nuclease cleavage products of both mock-infected and BHV-1-infected BEL cell nuclei produced monomers and multimers of unit fragment size which were indistinguishable from each other and displayed a typical nucleosome pattern on agarose gels. Southern analyses of micrococcal nuclease digests of infected cell nuclei indicated that some of the intranuclear BHV-1 DNA was present in a nucleosomal form. Three new proteins (with approximate molecular weights: 125,000, 42,000, and 17,000) were identified in chromatin isolated from BHV-1-infected BEL cells at ten hours p.i. These proteins were not present in mock-infected BEL cell chromatin. The 17,000 molecular weight protein was recognized by BHV-1 virion specific antisera. Neither of the two larger proteins appear to bind DNA from BHV-1. The smallest protein co-migrates with cellular histones, but no DNA binding proteins with the same molecular weight were found in the virion.