SEMINAR

The MRX/N complex ensures DSB repair fidelity through multiple pathways including Xrs2-FHA–dependent Tel1/ATM activation

Abstract
The DNA double-strand breaks (DSBs) are one of the most severe types of DNA damage and are most often repaired by homologous recombination (HR) or canonical non-homologous end joining (C-NHEJ). There are, however, several other minor pathways for DSB repair, some of which generate serious rearrangements of DNA structure. It is thought that an incorrect choice among these repair pathways promotes genomic instability, which can have many negative effects on biological activities, eventually promoting tumorigenesis. The Mre11-Rad50-Xrs2/Nbs1 (MRX/N) complex has many roles in the initial step of DSB repair and in the Tel1/ATM-related DNA damage response signaling(1). In humans, dysfunction of forkhead-associated (FHA) domain in Nbs1 causes Nijmegen breakage syndrome(2, 3), which confers a high risk of cancer and immunodeficiency, originally identified as an ataxia telangiectasia (AT)-like disorder (4). Here we show that the Xrs2 FHA domain of budding yeast is required both to suppress of imprecise repair of DSBs, as well as to promote the robust activation of Tel1, an ortholog of human ATM. The role of the FHA domain in Tel1 activation is independent of the well-known Tel1-binding activity of the Xrs2 C-terminus (5). Both the Xrs2 FHA domain and Tel1 were required for the timely removal of the Ku complex from DSB ends to suppress imprecise repair. Thus, the Xrs2 FHA domain and Tel1 kinase function work coordinately to maintain DSB repair fidelity.

References

1. T. Usui, H. Ogawa, J. H. Petrini, A DNA damage response pathway controlled by Tel1 and the Mre11 complex. Mol Cell 7, 1255-1266 (2001).

2. S. Matsuura et al., Positional cloning of the gene for Nijmegen breakage syndrome. Nat Genet 19, 179-181 (1998).

3. J. P. Carney et al., The hMre11/hRad50 protein complex and Nijmegen breakage syndrome: linkage of double-strand break repair to the cellular DNA damage response. Cell 93, 477-486 (1998).

4. K. M. Trujillo, P. Sung, DNA structure-specific nuclease activities in the Saccharomyces cerevisiae Rad50*Mre11 complex. The Journal of biological chemistry 276, 35458-35464 (2001).

5. H. Shima, M. Suzuki, M. Shinohara, Isolation and characterization of novel xrs2 mutations in Saccharomyces cerevisiae. Genetics 170, 71-85 (2005).

BIOGRAPHY

• 2007-present; Associate professor, Institute for Protein Research, Osaka University;
• 2004-2007; Research assistant, Institute for Protein Research, Osaka University;
• 2001-2004; Research assistant, Research Institute for Radiation Biology and Medicine, Hiroshima University;
• 2000-2001; Post-doctoral fellow, Graduate School of Science, Osaka University;
• 1998-2000; HFSP long-term fellow, Dept. of Radiation Oncology, Medical Center, University of Chicago;
• 1998; JSPS fellow, National Institute of Genetics;
• 1998; Ph.D., Graduate School of Medicine, Osaka University;

Research Field and Interests:
DNA double strand breaks (DSBs) are the most sever cytotoxic DNA lesion produced by ionizing radiation, or some chemical compounds. Imprecise repair of DSBs cause genomic instability, which often leads cell tumorigenesis. Not only that, because meiotic recombination is essential for proper segregation of homologous chromosomes during meiosis, germ cells must generate and repair programmed DSBs in a correct way. I am interested in the molecular mechanism of DSB repair process and its regulation both in mitosis and meiosis.

Selected Publications:
Shinohara, M., Hayashihara, K., Grubb, J.T., Bishop, D.K., and Shinohara, A. (2015). DNA damage response clamp 9-1-1 promotes assembly of ZMM proteins for formation of crossovers and synaptonemal complex. J Cell Sci 128, 1494-1506.

Terasawa, M., Shinohara, A., and Shinohara, M. (2014). Canonical non-homologous end joining in mitosis induces genome instability and is suppressed by M-phase-specific phosphorylation of XRCC4. PLoS Genet 10, e1004563.

Shinohara, M., and Shinohara, A. (2013). Multiple Pathways Suppress Non-Allelic Homologous Recombination during Meiosis in Saccharomyces cerevisiae. PLoS One 8, e63144.

Matsuzaki, K., Terasawa, M., Iwasaki, D., Higashide, M., and Shinohara, M. (2012). Cyclin-dependent kinase-dependent phosphorylation of Lif1 and Sae2 controls imprecise nonhomologous end joining accompanied by double-strand break resection. Genes Cells 17, 473-493.

Shinohara, M., Oh, S.D., Hunter, N., and Shinohara, A. (2008). Crossover assurance and crossover interference are distinctly regulated by the ZMM proteins during yeast meiosis. Nat Genet 40, 299-309.