A VIRAL GENE THAT ACTIVATES LYTIC CYCLE EXPRESSION OF KAPOSIS SARCOMA-ASSOCIATED HERPESVIRUS

Herpesviruses exist in two states, latency and a lytic productive cycl e. Here we identify an immediate early gene encoded by Kaposi's sarcom a-associated herpesvirus (KSHV)/human herpesvirus eight (HHV8) that ac tivates lytic cycle gene expression from the latent viral genome. The gene is a homologue of Rta, a transcriptional activator encoded by Eps tein-Barr virus (EBV). KSHV/Rta activated KSHV early lytic genes, incl uding virus-encoded interleukin 6 and polyadenylated nuclear RNA, and a late gene, small viral capsid antigen. In cells dually infected with Epstein-Barr virus and KSHV, each Rta activated only autologous lytic cycle genes. Expression of viral cytokines under control of the KSHV/ Rta gene is likely to contribute to the pathogenesis of KSHV-associate d diseases.