During latency, Kaposi's sarcoma-associated herpesvirus (KSHV) is thought to replicate once and to be partitioned in synchrony with the cell cycle of the host. In this replication cycle, the KSHV terminal repeat (TR) sequence functions as a replication origin, assisted by the latency-associated nuclear antigen (LANA). Thus, TR seems to function as a cis element for the replication and partitioning of the KSHV genome. Viral replication and partitioning are also likely to require cellular factors that interact with TR in either a LANA-dependent or -independent manner. Here, we sought to identify factors that associate with TR by using a TR DNA column and found that poly(ADP-ribose) polymerase 1 (PARP1) and known replication factors, including ORC2, CDC6, and Mcm7, bound to TR. PARP1 bound directly to a specific region within TR independent of LANA, and LANA was poly(ADP-ribosyl)ated by PARP1. Drugs such as hydroxyurea and niacinamide, which raise or lower PARP activity, respectively, affected the virus copy number in infected cells. Thus, the poly(ADP-ribosyl)ation status of LANA appears to affect the replication and/or maintenance of the viral genome. Drugs that specifically up-regulate PARP activity may lead to the disappearance of latent KSHV.
Copyright 2004 American Society for Microbiology