title: Suppression of DNA-damage checkpoint signaling by Rsk-mediated phosphorylation of Mre11.
abstract: Ataxia telangiectasia mutant (ATM) is an S/T-Q-directed kinase that is critical for the cellular response to double-stranded breaks (DSBs) in DNA. Following DNA damage, ATM is activated and recruited by the MRN protein complex [meiotic recombination 11 (Mre11)/DNA repair protein Rad50/Nijmegen breakage syndrome 1 proteins] to sites of DNA damage where ATM phosphorylates multiple substrates to trigger cell-cycle arrest. In cancer cells, this regulation may be faulty, and cell division may proceed even in the presence of damaged DNA. We show here that the ribosomal s6 kinase (Rsk), often elevated in cancers, can suppress DSB-induced ATM activation in both Xenopus egg extracts and human tumor cell lines. In analyzing each step in ATM activation, we have found that Rsk targets loading of MRN complex components onto DNA at DSB sites. Rsk can phosphorylate the Mre11 protein directly at S676 both in vitro and in intact cells and thereby can inhibit the binding of Mre11 to DNA with DSBs. Accordingly, mutation of S676 to Ala can reverse inhibition of the response to DSBs by Rsk. Collectively, these data point to Mre11 as an important locus of Rsk-mediated checkpoint inhibition acting upstream of ATM activation.
authors.affiliation: Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC 27710.
authors.forename: Chen
authors.initials: C
authors.lastname: Chen
authors.forename: Liguo
authors.initials: L
authors.lastname: Zhang
authors.forename: Nai-Jia
authors.initials: NJ
authors.lastname: Huang
authors.forename: Bofu
authors.initials: B
authors.lastname: Huang
authors.forename: Sally
authors.initials: S
authors.lastname: Kornbluth
mesh_terms: D017766:Acid Anhydride Hydrolases; D019943:Amino Acid Substitution; D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins / Q000235:genetics / Q000378:metabolism*; D059447:Cell Cycle Checkpoints; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002474:Cell-Free System / Q000378:metabolism; D053903:DNA Breaks, Double-Stranded; D045643:DNA Repair Enzymes / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D000076228:MRE11 Homologue Protein; D020125:Mutation, Missense; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D019893:Ribosomal Protein S6 Kinases / Q000235:genetics / Q000378:metabolism*; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C121766:MRE11 protein, human; C510917:Mre11 protein, Xenopus; C112156:NBN protein, human; D009687:Nuclear Proteins; D029867:Xenopus Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D019893:Ribosomal Protein S6 Kinases; D000076228:MRE11 Homologue Protein; D017766:Acid Anhydride Hydrolases; C112158:RAD50 protein, human; D045643:DNA Repair Enzymes
keywords: PMA; SL0101; dsDNA IP; γ-H2AX