title: Phosphorylation of SMC1 is a critical downstream event in the ATM-NBS1-BRCA1 pathway.
abstract: The ATM protein kinase is activated by intermolecular autophosphorylation in response to DNA damage and initiates cellular signaling pathways that facilitate cell survival and reduce chromosomal breakage. Here, we show that NBS1 and BRCA1 are required for the recruitment of previously activated ATM to the sites of DNA breaks after ionizing irradiation, and that this recruitment is required for the phosphorylation of SMC1 by ATM. To explore the functional importance of SMC1 phosphorylation, murine cells were generated, in which the two damage-induced phosphorylation sites in SMC1 are mutated. Although these cells demonstrate normal phosphorylation and focus formation of ATM, NBS1, and BRCA1 proteins after IR, they exhibit a defective S-phase checkpoint, decreased survival, and increased chromosomal aberrations after DNA damage. These observations suggest that many of the abnormal stress responses seen in cells lacking ATM, NBS1, or BRCA1 result from a failure of ATM migration to sites of DNA breaks and a resultant lack of SMC1 phosphorylation.
authors.affiliation: Department of Hematology-Oncology, St. Jude Children's Research Hospital, Memphis, Tennessee 38018, USA.
authors.forename: Risa
authors.initials: R
authors.lastname: Kitagawa
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Bakkenist
authors.forename: Peter J
authors.initials: PJ
authors.lastname: McKinnon
authors.forename: Michael B
authors.initials: MB
authors.lastname: Kastan
mesh_terms: D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D019313:BRCA1 Protein / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002470:Cell Survival; D002478:Cells, Cultured; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism*; D002869:Chromosome Aberrations; D004249:DNA Damage; D004268:DNA-Binding Proteins; D006801:Humans; D051379:Mice; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D021381:Protein Transport; D011839:Radiation, Ionizing; D015398:Signal Transduction; D025521:Tumor Suppressor Proteins; D000098550:Structural Maintenance of Chromosome Protein 1
chemical_list: D019313:BRCA1 Protein; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; C466108:Nijmegen breakage syndrome 1 protein, mouse; D009687:Nuclear Proteins; D025521:Tumor Suppressor Proteins; D000098550:Structural Maintenance of Chromosome Protein 1; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; D017346:Protein Serine-Threonine Kinases