title: Cell cycle-dependent complex formation of BRCA1.CtIP.MRN is important for DNA double-strand break repair.
abstract: BRCA1 plays an important role in the homologous recombination (HR)-mediated DNA double-strand break (DSB) repair, but the mechanism is not clear. Here we describe that BRCA1 forms a complex with CtIP and MRN (Mre11/Rad50/Nbs1) in a cell cycle-dependent manner. Significantly, the complex formation, especially the ionizing radiation-enhanced association of BRCA1 with MRN, requires cyclin-dependent kinase activity. CtIP directly interacts with Nbs1. The in vivo association of BRCA1 with MRN is largely dependent on the association of CtIP with the BRCT domains at the C terminus of BRCA1, whereas the N terminus of BRCA1 also contributes to its association with MRN. CtIP, as well as the interaction of BRCA1 with CtIP and MRN, is critical for IR-induced single-stranded DNA formation and cellular resistance to radiation. Consistently, CtIP itself is required for efficient HR-mediated DSB repair, like BRCA1 and MRN. These studies suggest that the complex formation of BRCA1.CtIP.MRN is important for facilitating DSB resection to generate single-stranded DNA that is needed for HR-mediated DSB repair. Because cyclin-dependent kinase is important for establishing IR-enhanced interaction of MRN with BRCA1, we propose that the cell cycle-dependent complex formation of BRCA1, CtIP, and MRN contributes to the activation of HR-mediated DSB repair in the S and G(2) phases of the cell cycle.
authors.affiliation: Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California 92037, USA.
authors.forename: Longchuan
authors.initials: L
authors.lastname: Chen
authors.forename: Christian J
authors.initials: CJ
authors.lastname: Nievera
authors.forename: Alan Yueh-Luen
authors.initials: AY
authors.lastname: Lee
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Wu
mesh_terms: D017766:Acid Anhydride Hydrolases; D019313:BRCA1 Protein / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D018844:Cyclin-Dependent Kinases / Q000235:genetics / Q000378:metabolism; D053903:DNA Breaks, Double-Stranded / Q000528:radiation effects; D045643:DNA Repair Enzymes / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004706:Endodeoxyribonucleases; D016195:G2 Phase / Q000502:physiology* / Q000528:radiation effects; D006801:Humans; D000076228:MRE11 Homologue Protein; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000235:genetics; D011839:Radiation, Ionizing; D016196:S Phase / Q000502:physiology* / Q000528:radiation effects
chemical_list: D019313:BRCA1 Protein; C492913:BRCA1 protein, human; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C121766:MRE11 protein, human; D046912:Multiprotein Complexes; C112156:NBN protein, human; D009687:Nuclear Proteins; D018844:Cyclin-Dependent Kinases; D004706:Endodeoxyribonucleases; D000076228:MRE11 Homologue Protein; C410741:RBBP8 protein, human; D017766:Acid Anhydride Hydrolases; C112158:RAD50 protein, human; D045643:DNA Repair Enzymes