The breast cancer tumor suppressor protein BRCA1 participates in multiple aspects of DNA damage responses. Its function in DNA double-strand break (DSB) repair, especially in homologous recombination (HR)-mediated DSB repair is highly relevant to its role in the maintenance of genome stability and tumor suppression. However, the molecular mechanism underlying this DSB repair function of BRCA1 is still not clear. Our proposed studies will focus on the investigation of how BRCA1 and the BRCA1-association protein CtIP participate in DSB repair, which will help to elucidate the mechanisms underlying BRCA1 function in tumor suppression. First, we will study cell cycle-dependent phosphorylation of CtIP and probe the biological significance of these phosphorylation events in HR-mediated DSB repair. Since CtIP is a critical player to bridge the interaction of BRCA1 with the repair protein complex Mre11/Rad50/Nbs1, understanding cell cycle-mediated regulation of CtIP is important for determining the exact role of BRCA1 in the activation of HR. Second, we will examine the enzymatic activities of CtIP and the BRCA1/CtIP/MRN complex on DNA, which will reveal the biochemical basis for the function of BRCA1 in DSB repair. Third, we will investigate the role of BRCA1 and CtIP in the repair of DSBs caused by replication fork collapse, and probe the importance of this repair activity in fragile site protection. Fourth, we will analyze the recruitment of CtIP to DSBs through a specific protein-protein interaction, which may promote the complex formation of BRCA1/CtIP/MRN at chromatin proximal to DSBs, thus facilitating HR-mediated DSB repair. Together, these studies will help to elucidate the molecular mechanisms underlying the critical function of BRCA1 and CtIP in the maintenance of genome stability and will provide significant insights into how BRCA1 functions as a tumor suppressor. The findings from these studies will also open new avenues towards novel therapeutic interventions for breast cancer prevention and treatment.

Public Health Relevance

BRCA1 is a breast cancer tumor suppressor, and germ line mutations in BRCA1 account for approximately 40% of hereditary breast cancers. We will investigate the role of BRCA1 and its association protein CtIP in DNA double-strand break repair, which is highly relevant to the tumor suppressor function of BRCA1. These studies will shed light on how BRCA1 is involved in the prevention of breast cancer and will help to open new avenues for developing therapeutic strategies for breast cancer prevention and treatment.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
Project #
Application #
Study Section
Radiation Therapeutics and Biology Study Section (RTB)
Program Officer
Pelroy, Richard
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Scripps Research Institute
La Jolla
United States
Zip Code
Wu, Yuehan; Lee, Suk-Hee; Williamson, Elizabeth A et al. (2015) EEPD1 Rescues Stressed Replication Forks and Maintains Genome Stability by Promoting End Resection and Homologous Recombination Repair. PLoS Genet 11:e1005675
Teixeira, Leonardo K; Wang, Xianlong; Li, Yongjiang et al. (2015) Cyclin E deregulation promotes loss of specific genomic regions. Curr Biol 25:1327-33
Makharashvili, Nodar; Tubbs, Anthony T; Yang, Soo-Hyun et al. (2014) Catalytic and noncatalytic roles of the CtIP endonuclease in double-strand break end resection. Mol Cell 54:1022-33
Wei, Na; Shi, Yi; Truong, Lan N et al. (2014) Oxidative stress diverts tRNA synthetase to nucleus for protection against DNA damage. Mol Cell 56:323-332
Truong, Lan N; Li, Yongjiang; Sun, Emily et al. (2014) Homologous recombination is a primary pathway to repair DNA double-strand breaks generated during DNA rereplication. J Biol Chem 289:28910-23
Wang, Hailong; Li, Yongjiang; Truong, Lan N et al. (2014) CtIP maintains stability at common fragile sites and inverted repeats by end resection-independent endonuclease activity. Mol Cell 54:1012-21
Truong, Lan N; Li, Yongjiang; Shi, Linda Z et al. (2013) Microhomology-mediated End Joining and Homologous Recombination share the initial end resection step to repair DNA double-strand breaks in mammalian cells. Proc Natl Acad Sci U S A 110:7720-5
Wang, Hailong; Shi, Linda Z; Wong, Catherine C L et al. (2013) The interaction of CtIP and Nbs1 connects CDK and ATM to regulate HR-mediated double-strand break repair. PLoS Genet 9:e1003277
Lu, Chi-Sheng; Truong, Lan N; Aslanian, Aaron et al. (2012) The RING finger protein RNF8 ubiquitinates Nbs1 to promote DNA double-strand break repair by homologous recombination. J Biol Chem 287:43984-94
He, Jing; Shi, Linda Z; Truong, Lan N et al. (2012) Rad50 zinc hook is important for the Mre11 complex to bind chromosomal DNA double-stranded breaks and initiate various DNA damage responses. J Biol Chem 287:31747-56

Showing the most recent 10 out of 13 publications