The majority of Kaposi’s sarcoma-associated herpesvirus (KSHV)-infected cells identified in vivo contain latent KSHV, with lytic replication in only a few percent of cells, as is the case for the cells of Kaposi’s sarcoma (KS) lesions. It interacts with the sugar-phosphate backbone of dsDNA and modulates viral and cellular transcription through largely undetermined mechanisms. We utilized a persistently HVS-infected A549 cell line, in which HVS DNA is stably maintained as nonintegrated circular episomes, to assess the role of the open reading frame 50 (ORF 50) (Rta) proteins in the latent-lytic switch. Thirty prominent protein bands were excised and subjected to high-performance liquid chromatography ion trap mass spectrometric analysis. WRN, which functions in cellular recombination pathways via its helicase and exonuclease activities, is not absolutely required for viral replication, as viral yields are only very slightly, if at all, decreased in WRN-deficient human primary fibroblasts compared to control cells. These findings suggest that HHV-8 has developed a novel mechanism to induce but then subvert the innate antiviral response, specifically the interferon-signaling pathway, to regulate RTA activity and ultimately the viral latent/lytic replicative cycle. This finding reveals a novel mechanism of gene regulation in the viral life cycle.
Smith, L. Like that of other herpesviruses, the life cycle of KSHV consists of latent and lytic phases (22). The switch from latency to lytic replication is initiated by the open reading frame 50 (ORF50)-encoded replication and transcription activator (RTA) protein. These results indicate that SIRT1 regulates KSHV latency by inhibiting different stages of viral lytic replication and link the cellular metabolic state with the KSHV life cycle. More importantly, the antiapoptotic and antiautophagic functions of vBcl-2 were not required for KSHV lytic replication. Taken together, these results suggest that the S-phase-specific DNA damage response to infection is dependent on the specific inhibition of the polymerase.