Broad Institute Inhibitors of Kaposi's Sarcoma Herpes virus LANA-C Inhibitor Probe Project
Kenneth Kaye,Department of Medicine, Channing Laboratory, Brigham and Women's Hospital, Harvard Medical School,firstname.lastname@example.org ..more
Kenneth Kaye,Department of Medicine, Channing Laboratory, Brigham and Women's Hospital, Harvard Medical School,email@example.com
Chantal Beauchemin,Department of Medicine, Channing Laboratory, Brigham and Women's Hospital, Harvard Medical School,firstname.lastname@example.org
The goal is to identify small molecules that suppress the binding of Kaposi's sarcoma herpesvirus (KSHV) LANA protein to its target DNA binding sequence in the viral genome. KSHV latently infects tumor cells, persisting as a multiple copy, circular, extrachromosomal episome (plasmid). Only a few percent of KS tumor cells or cells in primary effusion lymphoma (PEL)-derived cell lines contain KSHV undergoing lytic infection. To persist in latently infected, proliferating cells, episomes must replicate and efficiently segregate to the nuclei of progeny cells, similar to cellular DNA.
LANA is an 1162 amino acid protein that is one of several KSHV genes expressed during latent infection and is essential for viral persistence in infected cells. The viral protein acts as a molecular tether to bridge KSHV DNA to mitotic chromosomes and thus effect efficient episome segregation to daughter nuclei. LANA simultaneously binds core histones H2A/H2B to attach to mitotic chromosomes through its N-terminal region (N-LANA) and KSHV terminal repeat (TR) DNA through its C-terminal domain (C-LANA). This tethering mechanism efficiently segregates (episomal) genomes to daughter nuclei. Since tumor cells are dependent on KSHV infection for survival, disruption of LANA function with small molecules will result in tumor cell death. In the absence of tethering, viral episomes are destroyed in the cytoplasm and viral infection would be lost.
This project will screen for inhibitors of C-terminal LANA binding to KSHV terminal repeat (TR) DNA. C-terminal LANA binds a specific 20 bp DNA sequence within the KSHV TR. Such inhibitors will serve as valuable tools to investigate KSHV latency and LANA function and potentially provide a pathway for prevention and treatment of KSHV infection and malignancy. Probes will be required that do not bind or intercalate with DNA and must maintain activity in cells.
Kaposi's Sarcoma Herpes Virus, LANA, Latency-associated nuclear antigen
Kaposi's sarcoma-associated herpesvirus (KSHV) latency-associated nuclear antigen (LANA) is essential for persistence of viral genomes in tumor cells. Since KSHV-infected tumor cells become dependent on KSHV infection for survival, disruption of LANA function with small molecules would result in tumor cell death. LANA serves as a molecular tether to attach KSHV episomal genomes to mitotic chromosomes. LANA accomplishes this feat by simultaneously binding core histones in mitotic chromosomes through its N-terminal region and KSHV terminal repeat (TR) DNA through its C-terminal domain. This tethering mechanism results in efficient segregation of (episomal) genomes to daughter nuclei. In the absence of such tethering, viral episomes are destroyed in the cytoplasm and viral infection would be lost.
Currently, there are no small molecule inhibitors available that affect any aspect of LANA function. Since LANA is necessary for KSHV latent infection, chemical probes which block the essential LANA binding to viral DNA would serve as extremely useful reagents to investigate LANA and KSHV biology. Such inhibitory small molecules would be of potential therapeutic benefit since tumor cell persistence is dependent on KSHV infection.
Beyond the scope of MLPCN probe development, there are three main uses of a molecular probe discovered by this screening process: studies on episome maintenance, tethering and transcription regulation. Inhibitors of LANA would be the first inhibitors not only of KSHV, but of latent viral infection of any type. LANA inhibitors would serve as a model for inhibitors of the episomal tumor viruses EBV and papillomavirus, which use similar mechanisms to persist.