title: Checkpoint activation in response to double-strand breaks requires the Mre11/Rad50/Xrs2 complex.
abstract: Studies of human Nijmegen breakage syndrome (NBS) cells have led to the proposal that the Mre11/Rad50/ NBS1 complex, which is involved in the repair of DNA double-strand breaks (DSBs), might also function in activating the DNA damage checkpoint pathways after DSBs occur. We have studied the role of the homologous budding yeast complex, Mre11/Rad50/Xrs2, in checkpoint activation in response to DSB-inducing agents. Here we show that this complex is required for phosphorylation and activation of the Rad53 and Chk1 checkpoint kinases specifically in response to DSBs. Consistent with defective Rad53 activation, we observed defective cell-cycle delays after induction of DSBs in the absence of Mre11. Furthermore, after gamma-irradiation phosphorylation of Rad9, which is an early event in checkpoint activation, is also dependent on Mre11. All three components of the Mre11/Rad50/Xrs2 complex are required for activation of Rad53, however, the Ku80, Rad51 or Rad52 proteins, which are also involved in DSB repair, are not. Thus, the integrity of the Mre11/Rad50/Xrs2 complex is specifically required for checkpoint activation after the formation of DSBs.
authors.affiliation: ICRF Clare Hall Laboratories, CDC Laboratory, Blanche Lane, South Mimms, Potters Bar, Hertfordshire EN6 3LD, UK.
authors.forename: M
authors.initials: M
authors.lastname: Grenon
authors.forename: C
authors.initials: C
authors.lastname: Gilbert
authors.forename: N F
authors.initials: NF
authors.lastname: Lowndes
mesh_terms: D002453:Cell Cycle / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D018797:Cell Cycle Proteins / Q000378:metabolism; D002460:Cell Line; D004249:DNA Damage; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000378:metabolism; D004706:Endodeoxyribonucleases; D005090:Exodeoxyribonucleases; D005656:Fungal Proteins / Q000378:metabolism*; D016193:G1 Phase; D016195:G2 Phase; D005720:Gamma Rays; D006801:Humans; D000076228:MRE11 Homologue Protein; D010766:Phosphorylation; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C121766:MRE11 protein, human; C086930:RAD50 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C086929:XRS2 protein, S cerevisiae; C069930:rad9 protein; D004706:Endodeoxyribonucleases; D005090:Exodeoxyribonucleases; D000076228:MRE11 Homologue Protein; C094191:MRE11 protein, S cerevisiae