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Thesis Defense Announcement
To:  The George Mason University Community


Candidate: Amy T. Turner
Program: Master of Science in Biology

Date:   Thursday July 19, 2012
Time:   10:00 a.m.
Place:  George Mason University 
	    Occoquan Bldg., Room 203
	    Prince William campus
	
 
Thesis Chair: Dr. Yuntao Wu

Title: "PP1-alpha Knockdown by shRNA in CD4 T Cells Blocks HIV-1 Infection at the Levels
 of Nuclear Migration and Transcription"
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:
During HIV-1 infection of human resting CD4 T cells, viral gp120 engages the CXCR4 cellular co-receptor, inducing signal transduction and modulating cortical actin dynamics. This actin rearrangement is mediated by depolymerizing factor cofilin, which becomes activated upon dephosphorylation of serine 3 by phosphatases. It has previously been shown that cofilin is negatively regulated by LIM kinase-1 and positively regulated by phosphatases PP1, PP2A and SSH1. Here, we investigated the potential role of Protein Phosphatase 1, alpha isoform (PP1a) and SSH1 during gp120-induced cofilin activation. We created an shRNA vector to suppress SSH1 in human resting CD4 T cells, and found a slight increase in F-actin content, however the knockdown was too lethal to continue further studies. We also suppressed the catalytic subunit of PP1a and examined surface receptor expression, cofilin activation, actin change and overall viral infectivity in a stable CEM-SS derived cell line. We saw an increase in F-actin, an increase in phosphorylated cofilin, a decrease in CXCR4 surface expression and significant reduction in viral replication at the levels of nuclear migration and transcription. From this, we have concluded that PP1a is required for successful HIV-1 replication.

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