title: Mismatch-repair protein MSH6 is associated with Ku70 and regulates DNA double-strand break repair.
abstract: MSH6, a key component of the MSH2-MSH6 complex, plays a fundamental role in the repair of mismatched DNA bases. Herein, we report that MSH6 is a novel Ku70-interacting protein identified by yeast two-hybrid screening. Ku70 and Ku86 are two key regulatory subunits of the DNA-dependent protein kinase, which plays an essential role in repair of DNA double-strand breaks (DSBs) through the non-homologous end-joining (NEHJ) pathway. We found that association of Ku70 with MSH6 is enhanced in response to treatment with the radiomimetic drug neocarzinostatin (NCS) or ionizing radiation (IR), a potent inducer of DSBs. Furthermore, MSH6 exhibited diffuse nuclear staining in the majority of untreated cells and forms discrete nuclear foci after NCS or IR treatment. MSH6 colocalizes with γ-H2AX at sites of DNA damage after NCS or IR treatment. Cells depleted of MSH6 accumulate high levels of persistent DSBs, as detected by formation of γ-H2AX foci and by the comet assay. Moreover, MSH6-deficient cells were also shown to exhibit impaired NHEJ, which could be rescued by MSH6 overexpression. MSH6-deficient cells were hypersensitive to NCS- or IR-induced cell death, as revealed by a clonogenic cell-survival assay. These results suggest a potential role for MSH6 in DSB repair through upregulation of NHEJ by association with Ku70.
authors.affiliation: DNA Repair Research Center, Department of Pharmacology, Chosun University School of Medicine, 375 Seosuk-dong, Gwangju, 501-759, South Korea.
authors.forename: Ankita
authors.initials: A
authors.lastname: Shahi
authors.forename: Jung-Hee
authors.initials: JH
authors.lastname: Lee
authors.forename: Yoonsung
authors.initials: Y
authors.lastname: Kang
authors.forename: Sung Haeng
authors.initials: SH
authors.lastname: Lee
authors.forename: Jin-Won
authors.initials: JW
authors.lastname: Hyun
authors.forename: In-Youb
authors.initials: IY
authors.lastname: Chang
authors.forename: Jae-Yeoul
authors.initials: JY
authors.lastname: Jun
authors.forename: Ho Jin
authors.initials: HJ
authors.lastname: You
mesh_terms: D034961:Antigens, Nuclear / Q000378:metabolism*; D002460:Cell Line; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000502:physiology; D006657:Histones / Q000032:analysis; D006801:Humans; D000072200:Ku Autoantigen; D020798:Two-Hybrid System Techniques
chemical_list: D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; C094443:G-T mismatch-binding protein; C468783:H2AX protein, human; D006657:Histones; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen