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
	     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.


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.