The controlling role of ATM in homologous recombinational repair of DNA damage.
The human genetic disorder ataxia telangiectasia (A-T), caused by mutation in the ATM gene, is characterized by chromosomal instability, radiosensitivity and defective cell cycle checkpoint activation. DNA double-strand breaks (dsbs) persist in A-T cells after irradiation, but the underlying defect is unclear. To investigate ATM's interactions with dsb repair pathways, we disrupted ATM along with other genes involved in the principal, complementary dsb repair pathways of homologous recombination (HR) or non-homologous end-joining (NHEJ) in chicken DT40 cells. ATM(-/-) cells show altered kinetics of radiation-induced Rad51 and Rad54 focus formation. Ku70-deficient (NHEJ(-)) ATM(-/-) chicken DT40 cells show radiosensitivity and high radiation-induced chromosomal aberration frequencies, while Rad54-defective (HR(-)) ATM(-/-) cells show only slightly elevated aberration levels after irradiation, placing ATM and HR on the same pathway. These results reveal that ATM defects impair HR-mediated dsb repair and may link cell cycle checkpoints to HR activation.
Morrison
C
C
Bayer Chair Department of Molecular Immunology and Allergology, Faculty of Medicine, Kyoto University, Japan.
Sonoda
E
E
Takao
N
N
Shinohara
A
A
Yamamoto
K
K
Takeda
S
S
D000818:Animals; D034961:Antigens, Nuclear; D001260:Ataxia Telangiectasia / Q000235:genetics; D064007:Ataxia Telangiectasia Mutated Proteins; D030161:Avian Proteins; D018797:Cell Cycle Proteins; D002455:Cell Division / Q000235:genetics / Q000528:radiation effects; D002460:Cell Line; D002645:Chickens; D002869:Chromosome Aberrations / Q000235:genetics; D004249:DNA Damage / Q000235:genetics; D004265:DNA Helicases; D004260:DNA Repair / Q000235:genetics*; D045643:DNA Repair Enzymes; D004268:DNA-Binding Proteins / Q000235:genetics / Q000528:radiation effects; D005455:Fluorescent Antibody Technique; D005656:Fungal Proteins / Q000235:genetics / Q000528:radiation effects; D018390:Gene Targeting; D006801:Humans; D015151:Immunoblotting; D000072200:Ku Autoantigen; D009687:Nuclear Proteins / Q000235:genetics / Q000528:radiation effects; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D051135:Rad51 Recombinase; D011836:Radiation Tolerance / Q000235:genetics; D011995:Recombination, Genetic; D029701:Saccharomyces cerevisiae Proteins; D025521:Tumor Suppressor Proteins
D034961:Antigens, Nuclear; D030161:Avian Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; C495150:RAD51 protein, Gallus gallus; C495153:RAD51 protein, human; D051135:Rad51 Recombinase; C075468:RAD54 protein, S cerevisiae; D004265:DNA Helicases; C106893:XRCC5 protein, human; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen; D045643:DNA Repair Enzymes