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"Activated Notch is necessary but not sufficient for reactivation of Kaposiís sarcoma-associated herpesvirus: development of a novel viral reporter system and identification of differences between viral and cellular transcriptional activators"

by
Jennifer DeCotiis
.S. 2010, Seton Hall University, South Orange, NJ
Interdisciplinary Biomedical Sciences Program



Thesis Advisor: David Lukac, Ph.D.
Associate Professor
Department of Microbiology, Biochemistry, and Molecular Genetics

Monday, June 5, 2017
10:30 A.M., ICPH Auditorium


Abstract

The DNA tumor virus, Kaposi`s sarcoma-associated herpesvirus (KSHV), is the causative agent of two human cancers, Kaposi`s Sarcoma (KS) and primary effusion lymphoma (PEL), and a lymphoproliferation, Multicentric Castleman`s Disease (MCD). Progression to tumor development in KS is dependent upon reactivation of the virus from its latent state. Our lab has shown that the viral protein, Replication and transcriptional activator (Rta), is the only viral protein that is necessary and sufficient for viral reactivation. To induce reactivation and transcription of viral genes, Rta forms a complex with the DNA binding component of the Notch signaling pathway, recombination signal binding protein-1 for Jk (RBPJk). Formation of this Rta:RBPJk complex is necessary for viral reactivation to occur. Using a novel reporter virus, we showed that Rta, but none of the activated Notch isoforms, are capable of inducing viral reactivation. In addition, none of the well- characterized Notch 1 alleles with varying transactivation strengths are capable of reactivating KSHV. We then inhibited endogenous Notch through use of gamma secretase inhibitors, Notch specific siRNAs, and a dominant negative mastermind (MAML1) mutant. In all cases, reactivation was diminished by the decrease in activated Notch. This led us to conclude that Notch is necessary, but not sufficient for viral reactivation. Based on this information, we hypothesized that Rta and Notch isoforms 1-4 differ in their respective abilities to reactivate KSHV due to transactivation domain potency, and that Notch cooperates with Rta to reactivate KSHV.
Using our novel reporter virus, we tested chimeras of Rta and Notch isoform 1 for viral reactivation, and determined that Rtaís transactivation domain and DNA binding domain must be within the same protein for viral reactivation to occur. Furthermore, we were able to demonstrate cooperation of Rta and Notch in viral reactivation in our novel reporter system. However, further studies to determine if this cooperation was due to the formation of a Notch:Rta complex were inconclusive.


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