Studies on Epigenetically Active Latent Chromatin Maintenance

Deregulation of genome interactions through mutations at regulatory elements or mutation of responsible cellular nuclear enzymes result in multiple disorders. Although the significance of proper genomic-genomic interactions has been seen from disease phenotypes, the underlying molecular mechanisms of genomic looping regulation and the direct outcome of transcription are still not well connected. This partly stems from the highly complex nature of cellular promoter regulation, since it is controlled by multiple transcriptional factors and enhancer elements with significant noise within cell populations. Transcriptomics, genomics, and proteomics studies with recombinant Kaposi's sarcoma-associated herpesvirus (KSHV) episomes identified that the host cellular ChAHP (CHD4, ADNP, HP1) protein complex forms a stable protein complex with KSHV latency associated nuclear antigen (LANA) and plays essential roles in maintaining the inducibility of latent viral chromatin. The ChAHP complex is known to restrict cellular enhancer accessibility and regulates cell lineage, although how the protein complex regulates enhancer-promoter interaction remains unknown. Here, we hypothesize that the KSHV latency-lytic switch is a product of enhancer-promoter interactions regulated by the LANA-ChAHP complex. In this application, we will study how the KSHV episome is maintained as an inducible episome and if we can target the protein complex for therapeutic intervention. The molecular action of the LANA/ChAHP protein complex will be studied from three different perspectives; (i) biochemical, (ii) genetic, and (iii) protein complex structure. By taking advantage of defined enhancer-promoter pairs and convenient inducible mini viral chromatin, we will study enhancer-promoter regulations by dissecting ChAHP protein complex function. The proposed studies should not only benefit the understanding of the KSHV latency-lytic switch, but also provide insight into cellular inducible enhancer regulatory mechanisms.