title: Roles of nibrin and AtM/ATR kinases on the G2 checkpoint under endogenous or radio-induced DNA damage.
abstract: Checkpoint response to DNA damage involves the activation of DNA repair and G2 lengthening subpathways. The roles of nibrin (NBS1) and the ATM/ATR kinases in the G2 DNA damage checkpoint, evoked by endogenous and radio-induced DNA damage, were analyzed in control, A-T and NBS lymphoblast cell lines. Short-term responses to G2 treatments were evaluated by recording changes in the yield of chromosomal aberrations in the ensuing mitosis, due to G2 checkpoint adaptation, and also in the duration of G2 itself. The role of ATM/ATR in the G2 checkpoint pathway repairing chromosomal aberrations was unveiled by caffeine inhibition of both kinases in G2. In the control cell lines, nibrin and ATM cooperated to provide optimum G2 repair for endogenous DNA damage. In the A-T cells, ATR kinase substituted successfully for ATM, even though no G2 lengthening occurred. X-ray irradiation (0.4 Gy) in G2 increased chromosomal aberrations and lengthened G2, in both mutant and control cells. However, the repair of radio-induced DNA damage took place only in the controls. It was associated with nibrin-ATM interaction, and ATR did not substitute for ATM. The absence of nibrin prevented the repair of both endogenous and radio-induced DNA damage in the NBS cells and partially affected the induction of G2 lengthening.
authors.affiliation: Programa de Genética Humana, ICBM, Facultad de Medicina, Universidad de Chile, Casilla 70061, Santiago 7, Chile.
authors.forename: Katherine
authors.initials: K
authors.lastname: Marcelain
authors.forename: Consuelo
authors.initials: C
authors.lastname: De La Torre
authors.forename: Patricio
authors.initials: P
authors.lastname: González
authors.forename: Juana
authors.initials: J
authors.lastname: Pincheira
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins; D002110:Caffeine / Q000494:pharmacology; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000502:physiology*; D002460:Cell Line; D002869:Chromosome Aberrations; D004247:DNA / Q000187:drug effects / Q000528:radiation effects; D004249:DNA Damage; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000502:physiology*; D016195:G2 Phase / Q000235:genetics*; D018816:Genes, cdc; D006801:Humans; D009687:Nuclear Proteins / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D025521:Tumor Suppressor Proteins / Q000037:antagonists & inhibitors / Q000502:physiology*
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C112156:NBN protein, human; D009687:Nuclear Proteins; D025521:Tumor Suppressor Proteins; D002110:Caffeine; D004247:DNA; C576324:ATM protein, human; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases