Graduation Year
2025
Document Type
Dissertation
Degree
Ph.D.
Degree Name
Doctor of Philosophy (Ph.D.)
Degree Granting Department
Medical Sciences
Major Professor
Bala Chandran, Ph.D.
Committee Member
Robert Deschenes, Ph.D.
Committee Member
Burt Anderson, Ph.D.
Committee Member
Vrushank Davé, Ph.D.
Keywords
Herpesvirus, IFI16, HDAC, Deacetylation, DNA Binding, Promoter
Abstract
Kaposi’s Sarcoma Associated Herpes Virus (KSHV or HHV-8) is a γ-herpesvirus implicated in multiple lymphoproliferative human cancers and immune dysregulatory diseases. Like other herpesviruses, KSHV has a biphasic mode of infection primarily orchestrated by two viral proteins: the Latency-Associated Nuclear Antigen (LANA), which promotes viral persistence through latency, and the Replication and Transcription Activator (RTA), which triggers lytic reactivation. During latency, the KSHV genome exists as a highly heterochromatinized, extrachromosomal episome in the nucleus, which can be reverted to euchromatin in response to certain stimuli, like stress. KSHV has evolved to exploit numerous host proteins to orchestrate its lifecycle, especially its latent-lytic balance. In my research, I have elucidated a novel mechanism whereby KSHV exploits the host IFI16 protein to enhance LANA’s binding to KSHV promoters, thereby promoting their silencing.
The interferon-γ-inducible protein 16 (IFI16) is a nuclear innate immune antiviral restriction factor (RF) that detects viral dsDNAs. Our previous research demonstrated that IFI16 plays a crucial role in KSHV latency by modulating H3K9me3 deposition on the KSHV genome. In this study, I hypothesized that IFI16 modulates KSHV gene regulation in ways beyond H3K9me3 deposition. Analysis of the intracellular IFI16 interactome revealed that it binds to the class-I HDACs, HDAC1 and HDAC2. Previous reports have suggested that LANA undergoes lysine acetylation through unknown mechanisms, which results in the loss of its ability to bind to the KSHV transactivator protein (RTA) promoter. However, how the LANA acetylation-deacetylation cycle is orchestrated and what effect this has on KSHV gene expression remains unknown.
This study demonstrates that LANA, by default, undergoes acetylation post-translationally, and during latency, IFI16 interacts with this acetylated-LANA and recruits HDAC1/2 to it. This keeps LANA in a deacetylated form, competent in binding and repressing KSHV lytic promoters. However, during lytic reactivation, IFI16 is degraded via the proteasomal pathway, leading to the accumulation of acetylated LANA, which cannot bind to the RTA promoter. This results in the de-repression of the RTA promoter, driving reactivation. These findings shed new light on the role of IFI16 in KSHV latency and suggest that KSHV utilizes the cellular IFI16-HDAC1/2 interaction to facilitate its latency.
Scholar Commons Citation
Ghosh, Anandita, "Identification of Host Nuclear Factors Exploited by KSHV LANA to Maintain Latency" (2025). USF Tampa Graduate Theses and Dissertations.
https://digitalcommons.usf.edu/etd/10865
