Investigating the role of Epstein-Barr virus lytic key regulator protein Zta in transcriptional regulation

Almohammed, Rajaei (2017) Investigating the role of Epstein-Barr virus lytic key regulator protein Zta in transcriptional regulation. Doctoral thesis (PhD), University of Sussex.

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Abstract

Epstein-Barr virus (EBV) is a human herpes virus that, upon primary infection,
establishes life-long persistence in B cells (latency). One viral protein, the
immediate early lytic protein Zta (also known as BZLF1, ZEBRA, EB1, and Z)
plays a significant role in disturbing this latency and inducing a viral productive
(lytic) cycle. Expression of Zta, a basic leucine zipper transcription factor,
induces a cascade of viral lytic cycle gene expression. The activation of many
lytic genes requires the direct binding of Zta to its response elements (ZREs)
within proximal promoters of these genes. Much research in recent years has
focused on investigating Zta reactivation of latency and its role in lytic viral DNA
replication. This has revealed a wealth of knowledge about Zta as a
multifunctional transcription factor. However, a complete understanding of Zta
transcriptional activation is still missing. Here, utilising ChIP-qPCR, we showed
conserved binding patterns for Zta across several EBV lytic gene promoters in
two different EBV systems including a non-B cell EBV-infected cell line. Also,
using luciferase reporter assays, we show the first functional evidence for a
possible role of Zta in controlling transcription regulation at distal regulatory
elements (enhancers). Importantly, we identified BNLF2a, an essential viral
immune evasion gene, as a direct target for Zta. We identified five ZREs and
mapped functional ones within the BNLF2a promoter using mutational analysis
and luciferase reporter assays. We also expressed and purified a recombinant
GFP-bZIP Zta protein to address Zta binding to BNLF2a ZREs in vitro.
Interestingly, using in silico approach, we also identified a conserved sequence
in the ZRE flanking region of all five ZREs within BNLF2a promoter and
uncovered a role for a possible repressor at ZRE2 flanking region. Our work
not only adds to our understanding of Zta transcription regulation but
characterises for the first time the regulation of a novel Zta target that has a role
in evading the host immune system during EBV pre-latency and lytic cycle.

Item Type: Thesis (Doctoral)
Schools and Departments: School of Life Sciences > Biochemistry
Subjects: Q Science > QR Microbiology > QR0355 Virology
Depositing User: Library Cataloguing
Date Deposited: 21 Feb 2017 15:36
Last Modified: 21 Feb 2017 15:36
URI: http://sro.sussex.ac.uk/id/eprint/66840

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