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D ow nloaded from 2 Abstract 1 Kaposi's sarcoma-associated herpesvirus (KSHV, HHV8) is implicated in the 2 pathogenesis of many human malignancies including Kaposi's sarcoma (KS), 3 multicentric Castleman's disease (MCD) and primary effusion lymphoma (PEL). KSHV 4 infection displays two alternative life cycles referred to as the latent and lytic or 5 productive cycle. Previously, we have reported that RTA, a major lytic cycle 6 transactivator contributes to the development of KSHV latency by inducing LANA 7 expression during early stages of infection by targeting RBP-Jκ, the master regulator of 8 the Notch signaling pathway. Here, we generated a BAC KSHV recombinant virus 9 deleted for the RBP-Jκ site within the LANA promoter to evaluate the function of the 10 RBP-Jκ cognate site in establishing primary latent infection. The results showed that 11 genetic disruption of the RBP-Jκ binding site within the KSHV LANA promoter led to 12 enhanced expression of KSHV encoded immediate early replication and transcription 13 activator (RTA) resulting in an increase in lytic replication during primary infection of 14 human peripheral blood mononuclear cells (PBMCs). This system provides a powerful 15 tool for use in indentifying additional cellular and viral molecules involved in LANA 16 mediated latency maintenance during the early stages of KSHV infection. 1