One of the key aims of cancer research is to understand how cells detect and repair double-strand breaks (DSBs) in DNA. DSBs are important because they are a major source of genome instability that is a hallmark of cancer. Moreover, many of the most widely used and effective anti-cancer therapies use targeted irradiation or chemotherapeutics to create DSBs, which preferentially kill cancer cells. The Mre11-Rad50-Nbs1 (MRN) protein complex, its repair cofactor Ctp1/CtIP/Sae2, and its checkpoint signaling cofactor Tel1/ATM, have evolutionary conserved functions that are crucial for detecting and repairing DSBs, and for activating the DNA damage checkpoint that arrests cell division. Fission yeast mutants lacking MRN or Ctp1 are unable to repair DSBs, and therefore display genomic instability and are acutely sensitive to clastogens. Human genetic diseases that partially impair the functions of these proteins cause genome instability syndromes. Notably, hypomorphic mutations in human Nbs1 cause microcephaly, developmental abnormalities, immunodeficiency, radiation sensitivity and cancer predisposition. Recent studies revealed that Nbs1 functions as a molecular tether that links Ctp1 and Tel1 to the Mre11-Rad50 complex. In this project, we propose to use genetic, cell biological and in vivo assays to characterize the functional interactions between the MRN complex and Ctp1 at DSBs formed by replication fork collapse. These studies will improve the conceptual understanding of how mutations in human Nbs1 cause cancer, and in doing so enhance opportunities for developing new strategies for cancer prevention and treatment.

Public Health Relevance

The Mre11-Rad50-Nbs1 protein complex, Ctp1 (CtIP) and Tel1 (ATM) protect genome integrity and prevent cancer causing mutations by detecting, signaling and repairing DNA double-strand breaks. This project will define the functional interactions amongst these proteins, and thereby identify new potential anti- cancer strategies. !

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
Project #
Application #
Study Section
Molecular Genetics B Study Section (MGB)
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
Deshpande, Rajashree A; Williams, Gareth J; Limbo, Oliver et al. (2014) ATP-driven Rad50 conformations regulate DNA tethering, end resection, and ATM checkpoint signaling. EMBO J 33:482-500
Wei, Yi; Wang, Hai-Tao; Zhai, Yonggong et al. (2014) Mdb1, a fission yeast homolog of human MDC1, modulates DNA damage response and mitotic spindle function. PLoS One 9:e97028
Lee, Si Young; Rozenzhak, Sophie; Russell, Paul (2013) ?H2A-binding protein Brc1 affects centromere function in fission yeast. Mol Cell Biol 33:1410-6
Lee, Si Young; Russell, Paul (2013) Brc1 links replication stress response and centromere function. Cell Cycle 12:1665-71
Dodson, Gerald E; Russell, Paul (2011) Enhanced Tel1(ATM) checkpoint signaling at protein-bound double-strand breaks. Mol Cell Biol 31:1936-7
Williams, Gareth J; Williams, R Scott; Williams, Jessica S et al. (2011) ABC ATPase signature helices in Rad50 link nucleotide state to Mre11 interface for DNA repair. Nat Struct Mol Biol 18:423-31
Limbo, Oliver; Porter-Goff, Mary E; Rhind, Nicholas et al. (2011) Mre11 nuclease activity and Ctp1 regulate Chk1 activation by Rad3ATR and Tel1ATM checkpoint kinases at double-strand breaks. Mol Cell Biol 31:573-83
Langerak, Petra; Russell, Paul (2011) Regulatory networks integrating cell cycle control with DNA damage checkpoints and double-strand break repair. Philos Trans R Soc Lond B Biol Sci 366:3562-71
Langerak, Petra; Mejia-Ramirez, Eva; Limbo, Oliver et al. (2011) Release of Ku and MRN from DNA ends by Mre11 nuclease activity and Ctp1 is required for homologous recombination repair of double-strand breaks. PLoS Genet 7:e1002271
Williams, Jessica S; Williams, R Scott; Dovey, Claire L et al. (2010) gammaH2A binds Brc1 to maintain genome integrity during S-phase. EMBO J 29:1136-48

Showing the most recent 10 out of 31 publications