The long-term goal of this research project is to understand the regulation BRCA1 function and to provide new insights into the etiology of breast and ovarian cancer and also provide new targets for the development of novel therapeutic agents. The loss of function of the BRCA1 gene is associated with breast and ovarian cancer. BRCA1 protein has been implicated in fundamental cellular functions, such as DMA repair, recombination, cell cycle regulation and gene transcription. The phosphorylation status of BRCA1 is important for its function. BRCA1 is expressed and phosphorylated in a cell cycle dependent manner and BRCA1 phosphorylation also occurs immediately after DNA damage. Phosphorylation of BRCA1 by kinases such as ATM, ATR, and hCds1, is involved in G2 arrest, which allows cells to undergo DNA damage repair. Once DNA repair is accomplished, cells can be released from G2 arrest and enter mitosis. BRCA1 in mitotic cells is mostly hypophosphorylated. We have demonstrated that protein phosphatase 1 alpha (PP1 alpha) interacts with BRCA1 and dephosphorylates BRCA1 phosphorylated by hCds1. The objective of this proposal is to study the functional significance of this interaction. We hypothesize that PP1 is a critical negative regulator of BRCA1 function. We further hypothesize that dephosphorylation of BRCA1 by PP1 serves as a signal for completion of DNA repair and is involved in G2/M cell cycle progression. We will test this hypothesis by providing functional evidence to support the idea that PP1 regulates fundamental BRCA1 function. We will perform a detailed molecular analysis to determine if PP1 alpha is also responsible for dephosphorylation of BRCA1 phosphorylated by ATM and ATR, and test whether PP1 alpha regulates G2/M progression through dephosphorylation of BRCA1. We have identified a PP1-binding site in BRCA1 and will interrupt the interaction between BRCA1 and PP1 using PP1 non-binding BRCA1 mutants, and dominant-negative truncated BRCA1 proteins containing the PP1-binding motif to investigate whether PP1-binding and dephosphorylation of BRCA1 affect cell survival after DNA damage by modulating cell cycle progression and DNA repair. Lastly, we will also identify regulators of PP1 alpha activity toward BRCA1. ? ?

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
1R01CA111436-01A1
Application #
6965584
Study Section
Cancer Molecular Pathobiology Study Section (CAMP)
Program Officer
Pelroy, Richard
Project Start
2005-07-01
Project End
2009-04-30
Budget Start
2005-07-01
Budget End
2006-04-30
Support Year
1
Fiscal Year
2005
Total Cost
$196,080
Indirect Cost
Name
Magee-Women's Research Institute and Foundation
Department
Type
DUNS #
119132785
City
Pittsburgh
State
PA
Country
United States
Zip Code
15213
Chen, Bert Yu-Hung; Huang, Cheng-Hsiang; Lin, Ying-Hsi et al. (2014) The K898E germline variant in the PP1-binding motif of BRCA1 causes defects in DNA Repair. Sci Rep 4:5812
Chang, Hung-Chi; Yang, Su-Fu; Huang, Ching-Chun et al. (2013) Development of a novel non-radioactive cell-based method for the screening of SGLT1 and SGLT2 inhibitors using 1-NBDG. Mol Biosyst 9:2010-20
Hsu, Lih-Ching; Durrant, David E; Huang, Ching-Chun et al. (2012) Development of hemiasterlin derivatives as potential anticancer agents that inhibit tubulin polymerization and synergize with a stilbene tubulin inhibitor. Invest New Drugs 30:1379-88
Yu, Young-Mi; Pace, Serena M; Allen, Susan R et al. (2008) A PP1-binding motif present in BRCA1 plays a role in its DNA repair function. Int J Biol Sci 4:352-61
Hsu, Lih-Ching (2007) Identification and functional characterization of a PP1-binding site in BRCA1. Biochem Biophys Res Commun 360:507-12
Hsu, L-C; Huang, X; Seasholtz, S et al. (2006) Gene amplification and overexpression of protein phosphatase 1alpha in oral squamous cell carcinoma cell lines. Oncogene 25:5517-26