The Epstein-Barr virus is the etiologic agent of infectious mononucleosis and is associated with Burkitt's lymphoma and nasopharyngeal carcinoma. This research project will study the gene regulation of the Epstein-Barr virus at the transcriptional level, and investigate possible interactions between the EBV and HIV viruses. To accomplish this goal, a representative promoter unit from each of the four types of EBV genes (latent, immediate- early, early and late) will be placed upstream of the bacterial CAT (chloramphenicol acetyl transferase) gene. The EBV-CAT vectors will then be used to ask such questions as whether any of the EBV promoters have tissue specific activity, whether there are EBV encoded promoters which function in trans to activate other EBV gene promoters, and whether the differential expression of latent versus non-latent genes is regulated interaction of the EBV and HIV viruses at the molecular level, since patients with AIDS have high frequency of EBV-associated lymphomas. Using CAT vectors containing either EBV or HIV promoters, we will investigate whether the HIV TAT protein is able to transactivate the EBV promoters, and likewise, whether EBV encoded proteins can transactivate the HIV promoter.