Epstein-Barr virus (EBV) is a gammaherpesvirus that persistently infects more than 90% of the human population and its latent infection is associated with several malignancies. EBNA1 is the only viral protein required for the persistence of EBV episomes through its contributions to the replication, mitotic segregation of EBV episomes, and transcriptional activation of viral latency genes. These functions require EBNA1 binding to the DNA elements within the EBV genome that are important for transcription and replication, and interactions of EBNA1 with cellular factors. The aim of this thesis is to characterize the functional significance of the interactions between EBNA1 and chromatin-associated proteins NAP1, TAF-I, and Brd4, particularly in EBNA1-mediated transcription and DNA replication. Here I investigated the interactions of EBNA1 with NAP1 or TAF-I that were previously discovered in our laboratory by proteomic methods. I found that EBNA1 binds directly to NAP1 and to the β isoform of TAF-I, resulting in increased solubility of EBNA1 in vitro. Brd4 was also found to bind to EBNA1 and this interaction is mediated by an EBNA1 sequence essential for transactivation. Brd4, NAP1 and TAF-I all localize with EBNA1 to the transcriptional element and alteration of their levels inhibits transcriptional activation, suggesting that these proteins contribute to EBNA1-dependent transactivation through protein complex formation at the transcriptional element. On the other hand, only TAF-I is recruited to the origin of replication by EBNA1 and acts as a repressor for EBNA1-mediated DNA replication. My data suggest that this negative regulation is linked to TAF-I’s ability to interfere with histone methylation and thus to alter chromatin structure at the origin of DNA replication. Finally, I showed that NAP1 and TAF-I are required for expression of lytic protein BZLF1 and that TAF-I associates with the BZLF1 promoter during lytic reactivation.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:OTU.1807/32845 |
| Date | 31 August 2012 |
| Creators | Wang, Shan |
| Contributors | Frappier, Lori |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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