Kaposi's sarcoma (KS)-associated herpesvirus (KSHV or HHV8) is the causative agent of KS, primary effusion lymphoma (PEL) and multicentric Castleman's disease. KSHV is spread person to person through saliva. KSHV tumors occur primarily in AIDS and other immune compromised states. There are no available specific therapies for these tumors. KS is the leading AIDS malignancy and is epidemic in sub Saharan Africa where coinfection with HIV is common. KS often involves the oral cavity and visceral organs. KSHV latently infects tumor cells. During latent infection viral genomes persist as multiple copy, extrachromosomal, circular episomes (plasmids). To persist in proliferating cells, episomes must replicate with each cell cycle and efficiently segregate to daughter nuclei. The latency-associated nuclear antigen (LANA) mediates KSHV episome persistence and is strictly required for viral latency and KSHV survival in proliferating cells. Episome maintanence is comprised of two components: replication of KSHV DNA, and segregation of replicated episomes to daughter cell nuclei. LANA is responsible for both these functions. To replicate KSHV DNA, LANA binds viral terminal repeat (TR) DNA. Since no KSHV DNA replication proteins are expressed during latent infection, LANA is responsible for recruiting host cell replication machinery. Although LANA interacts with several cell replication factors, little is known regarding the underlying mechanisms through which LANA mediates replication. We recently found that LANA recruits the DNA polymerase clamp loader to mediate efficient replication and viral persistence. Loss of this recruitment greatly inhibited LANA's ability to mediate DNA replication and resulted in loss of virus infection. These findings suggested that clamp loading is a rate-limiting step in DNA replication that is incompatible with virus survival. LANA enhancement of clamp loading enables KSHV replication, persistence, and survival. The overarching hypothesis of this application is that LANA's recruitment of the clamp loader is a fundamental component of KSHV replication biology that is an ideal target for potential therapeutic inhibition. Experiments will test this hypothesis. Work will assess the mechanism by which LANA enhances clamp loading. Experiments will investigate the architecture of the LANA-clamp loader complex. In addition, experiments will target the LANA-clamp loader complex for inhibition. The expected outcome of this work is a detailed understanding of the mechanism through which LANA acts on the clamp loader and validation of this interaction as a potential therapeutic target for KSHV malignancy.
Kaposi's sarcoma-associated herpesvirus (KSHV) has a causative role in several human cancers. KSHV infects tumor cells and persists in a state of latency. This project investigates a critical underlying process that KSHV uses to replicate, which is necessary in order to maintain latent infection. A better understanding of this viral process may allow development of strategies which prevent KSHV cancers.
