Dissertation Defense Announcement
To: The George Mason University Community
Candidate: Irene Guendel
Program: PhD in Biosciences
Date: Wednesday April 23, 2014
Time: 9:00 a.m.
Place: George Mason University
Prince William Campus
Bull Run Hall, Room 248
Title: "BRCA1 Functions as a Novel Transcriptional Cofactor in HIV-1 Infection"
Thesis Director: Dr. Kylene Kehn-Hall
Thesis Committee: Dr. Monique van Hoek, Dr. Daniel N. Cox, Dr. Barney Bishop
A copy of the dissertation will be available in the Mercer Library. All are invited to attend the defense.
Viruses have naturally evolved elegant strategies to manipulate the host’s cellular machinery, including ways to hijack cellular DNA repair proteins in order to aid in their own replication. Retroviruses induce DNA damage through integration of their genome into the host DNA. DNA damage signaling proteins including ATR, ATM and BRCA1 have been shown to contribute to multiple steps in the HIV-1 life cycle, including integration and Vpr-induced G2/M arrest. However, there have been no studies to date regarding the role of BRCA1 on HIV-1 transcription. Our results indicated that BRCA1 phosphorylation, specifically p-BRCA1 S1423, was increased and altered during cell cycle progression in HIV-1 infected cells. Size-exclusion chromatography experiments showed that BRCA1 eluted in the same fraction as other cellular proteins involved in HIV-1 transcription, including Cyclin T1, Cdk9 and Baf170. BRCA1 was found to be important for viral transcription as cells that lack BRCA1 displayed severely reduced HIV-1 Tat-dependent transcription, and overexpression or selective depletion resulted in enhanced or decreased transcription. Moreover, small molecule inhibition of BRCA1 phosphorylation effector kinases, ATR and ATM, decreased Tat-dependent transcription in a dose-dependent manner, whereas Chk2 inhibitor showed no effect. Furthermore, both curcumin and the ATM inhibitor, KU55933, decreased BRCA1 LTR occupancy. In addition, Tat was found to associate with Tat at the BRCA1 aa504-802 region. These results suggest that HIV-1 infection upregulates expression and phosphorylation of BRCA1 and may utilize its transcriptional cofactor function for efficient transcription. The presence of BRCA1 at the HIV-1 promoter highlights a novel function of the multifaceted protein in HIV infection. The BRCA1 pathway or enzymes that phosphorylate BRCA1 could potentially be used as complementary cART host-based treatment, as there are multiple potent ATM inhibitors in development as chemotherapeutics.