Understanding the high mutation frequency of cancer cells is key to finding ways to prevent or delay the onset of disease and subsequent chemoresistance. Errors in repair of DNA double-strand breaks (DSBs) can cause mutations, hence understanding how repair pathways act is of essential importance for the development of new strategies to reduce the frequency of tumors and the appearance of chemoresistance. Mammalian DSB repair is mediated by nonhomologous end-joining (NHEJ) and homologous recombination (HR). Whereas HR uses a homologous template for repair, NHEJ acts by ligation of DSBs. The pathways therefore produce different repair outcomes, and the relative rate of usage of NHEJ and HR is regulated in cells by processes which are poorly understood. Cell cycle appears to be a major determinant of usage of the HR pathway, with HR used infrequently in G1 somatic cells. A second regulator of pathway choice is the DNA damage response factor, 53BP1. 53BP1 limits resection of DSBs, a key step in HR. 53BP1 therefore promotes NHEJ at the expense of HR. Using genetic approaches in primary mouse cells, we propose to measure how 53BP1 interacts with cellular activities including BRCA1, BLM and Exo1 to mediate DSB resection, a key step regulating the use of HR versus NHEJ. We will furthermore test whether the effect of 53BP1 in limiting resection is required for suppressing genomic instability and tumorigenesis arising from defects in DNA repair in non-dividing cells. Finally, we propose to determine how BRCA1 interacts with PALB2, a repair factor that helps recruit BRCA2 to break sites. BRCA1 and PALB2 form a complex through interactions of predicted coiled-coil regions, and we will identify and characterize the exact molecular mechanism of interaction using biophysical and cell biology techniques. Together, these studies will advance our understanding of critical commitment steps to HR in primary mammalian cells, and inform strategies for the design of rational therapies for treatment of individuals with mutations in key DNA repair genes.
Cells have systems for repairing damage to DNA, and these systems normally prevent the appearance of the mutations that drive growth of cancer cells. Understanding how repair systems operate will enable us design therapies to effectively treat patients with cells that have deficient repair systems. In particular, we aim to understand steps leading to the use of homologous recombination, a repair system that corrects DNA damage without mutation.
|Simhadri, Srilatha; Vincelli, Gabriele; Huo, Yanying et al. (2018) PALB2 connects BRCA1 and BRCA2 in the G2/M checkpoint response. Oncogene :|
|Her, Joonyoung; Ray, Chandni; Altshuler, Jake et al. (2018) 53BP1 Mediates ATR-Chk1 Signaling and Protects Replication Forks under Conditions of Replication Stress. Mol Cell Biol 38:|
|Her, Joonyoung; Bunting, Samuel F (2018) How cells ensure correct repair of DNA double-strand breaks. J Biol Chem 293:10502-10511|
|Sharma, Pragati; Mullen, Janet R; Li, Minxing et al. (2017) A Lysine Desert Protects a Novel Domain in the Slx5-Slx8 SUMO Targeted Ub Ligase To Maintain Sumoylation Levels in Saccharomyces cerevisiae. Genetics 206:1807-1821|
|Hong, Xuehui; Liu, Wenyu; Song, Ruipeng et al. (2016) SOX9 is targeted for proteasomal degradation by the E3 ligase FBW7 in response to DNA damage. Nucleic Acids Res 44:8855-8869|
|Li, Minxing; Cole, Francesca; Patel, Dharm S et al. (2016) 53BP1 ablation rescues genomic instability in mice expressing 'RING-less' BRCA1. EMBO Rep 17:1532-1541|
|Vazquez, Berta N; Thackray, Joshua K; Simonet, Nicolas G et al. (2016) SIRT7 promotes genome integrity and modulates non-homologous end joining DNA repair. EMBO J 35:1488-503|
|Polato, Federica; Callen, Elsa; Wong, Nancy et al. (2014) CtIP-mediated resection is essential for viability and can operate independently of BRCA1. J Exp Med 211:1027-36|
|Bowman-Colin, Christian; Xia, Bing; Bunting, Samuel et al. (2013) Palb2 synergizes with Trp53 to suppress mammary tumor formation in a model of inherited breast cancer. Proc Natl Acad Sci U S A 110:8632-7|