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Thesis Defense Announcement
To:  The George Mason University Community

*Candidate: Dana E. Grindel
Program: Master of Science in Biology
*
*Date:   Thursday July 28, 2011
Time:   10:00 a.m.
Place:  George Mason University, Prince William campus <http://www.gmu.edu/resources/visitors/findex.html>
	     Bull Run Hall, Room 246
 
*Thesis Chair:  Dr. Kylene Kehn-Hall

Title: "The Role of P53 Signaling in Rift Valley Fever Virus Infection"***
*

A copy of the thesis is on reserve in the Johnson Center Library, 
Fairfax campus.  The thesis will not be read at the meeting, but should 
be read in advance. All members of the George Mason University community 
are invited to attend.

*ABSTRACT:*

Rift Valley fever virus (RVFV) is part of a diverse group of viruses 
that cause potentially fatal hemorrhagic fever.  These hemorrhagic fever 
viruses (HFV) are responsible for high levels of both mortality and 
morbidity in infected patients and have been implicated in wide economic 
loss in the agricultural industry due to its deleterious effects on 
livestock.  Recently, RVFV has been classified as a possible weapon for 
bioterrorism.  Given this, it is important to understand the factors 
involved in the pathogenicity and virulence of RVFV.  This could lead to 
the development of therapeutics of which there are currently none.  This 
research aims to elucidate the role of p53 signaling in RVFV infection 
and viral replication. Studies have shown that upon infection, certain 
viruses have the capability of utilizing particular cellular signaling 
pathways to propagate viral infection. Activation of p53 is important 
for the DNA damage signaling cascade, initiation of apoptosis, cell 
cycle arrest and transcriptional regulation of hundreds of genes.  These 
signaling pathways could serve as an attractive target for manipulation 
by RVFV.  A previous study using Reverse Phase Proteomic Analysis (RMPA) 
identified p53 phosphorylation as being highly upregulated on two 
residues (Ser15 and Ser46) following infection with RVFV.  Western blot 
analysis of these as well as several other p53 phosphorylation sites 
(Ser9, Ser20, Ser37) confirmed upregulated phosphorylation of p53 
following infection with RVFV.  In addition, western blot analysis after 
infection with mutant viruses lacking either functional NSs or NSm viral 
proteins, show that the p53 phosphorylation is dependent on NSs but not 
on NSm. Furthermore, confocal microscopy imaging of immunostained p53 
shows localization of p53 within the nucleus following infection with 
RVFV.  We next sought to characterize the role of p53 signaling on RVFV 
induced cell death with cell viability assays using both Wild Type (WT) 
p53 cells and mutant p53 cell lines. The results of these experiments 
show increased cell survivability upon RVFV infection in the p53 mutant 
cell lines.  Similar experiments using p53 null cells confirm these 
results.  To determine the influence of p53 on RVFV viral replication, 
plaque assays were performed using the p53 WT and p53 null cell lines at 
different multiplicity of infections (MOIs).  P53 null cells showed 
decreased viral titers at each MOI as compared to the WT p53 cells, 
suggesting RVFV utilizes p53 during viral replication.  The collective 
results of these experiments indicate that the p53 signaling pathway is 
utilized during RVFV infection to induce cell death and increase viral 
replication.  

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