VIRAL-PROTEINS ASSOCIATED WITH THE EPSTEIN-BARR-VIRUS TRANSACTIVATOR, ZEBRA

The BamHI Z Epstein-Barr replication activator (ZEBRA) mediates disruption of latency and induction of Epstein-Barr virus (EBV) early gene expression in latently infected lymphocytes. Polyclonal rabbit sera raised against ZEBRA were used to immunoprecipitate ZEBRA-associated proteins (ZAPs). ZAPs of 19, 21, 23, and 42 kDa were co-immunoprecipitated with ZEBRA from extracts of EBV-producing lymphoid cell lines. ZAPs were not recognized directly by the rabbit sera, but they were antigenic for EBV+ human sera. Immunoprecipitation of ZAPs by ZEBRA-specific antisera required the presence of ZEBRA. ZAPs were not coprecipitated with ZEBRA from mouse cells expressing only ZEBRA, from Raji (a cell line in which EBV is unable to complete lytic replication), or from cells treated with inhibitors of viral DNA synthesis. Thus, ZAPs are late EBV-encoded proteins. ZEBRA and ZAPs colocalized to a salt-insoluble nuclear fraction, and both were found extracellularly in crude preparations of virions. ZAPs might function to affect the cellular localization of ZEBRA, to alter its capacity to transactivate, or to influence its target gene specificity.