Roles of DNA-dependent protein kinase and ATM in cell-cycle-dependent radiation sensitivity in human cells.
OBJECTIVE
The roles of DNA-dependent protein kinase (DNA-PK) and ATM in the cell-cycle-dependent radiosensitivity in human cells were investigated.


METHODS
A DNA-PK activity-deficient human glioblastoma cell line M059J, ataxia telangiectasia cell lines AT3BISV and AT5BIVA, and control cell lines were used. Wortmannin inhibited DNA-PK and ATM activities. Cells were synchronized by hydroxyurea. Progression through the cell cycle was analysed by flow cytometry.


RESULTS
M059J exhibited hyper-radiosensitivity throughout the cell cycle, with extreme hyper-radiosensitivity in G to early S-phase compared with the control cell line M059K. AT3BISV and AT5BIVA exhibited hyper-radiosensitivity throughout the cell cycle but showed a similar pattern of cell-cycle-dependent radiosensitivity to that observed in LM217 or HeLa cells. In AT3BISV and AT5BIVA, radiosensitization by wortmannin was observed throughout the cell cycle and was most prominent in G1 to early S-phase. Wortmannin did not sensitize M059J to ionizing radiation in any cell-cycle phase. DNA-PK activities were not different throughout the cell cycle.


CONCLUSIONS
The results suggest that (1) non-homologous endjoining plays a dominant role in G1 to early S-phase and a minor role in late S to G2-phase in repairing DNA double-strand breaks, (2) the role of ATM in repairing double-strand breaks may be almost cell-cycle-independent and (3) the dominant role of non-homologous end-joining during G1 to early S-phase is not due to cell-cycle-dependent fluctuations in DNA-PK activity.
Yoshida
M
M
Departments of Radiation Research and Radiology, Tohoku University School of Medicine, Sendai, Japan.
Hosoi
Y
Y
Miyachi
H
H
Ishii
N
N
Matsumoto
Y
Y
Enomoto
A
A
Nakagawa
K
K
Yamada
S
S
Suzuki
N
N
Ono
T
T
D000730:Androstadienes / Q000494:pharmacology; D001260:Ataxia Telangiectasia / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy; D064007:Ataxia Telangiectasia Mutated Proteins; D002453:Cell Cycle / Q000502:physiology / Q000528:radiation effects*; D018797:Cell Cycle Proteins; D002460:Cell Line; D002470:Cell Survival / Q000528:radiation effects; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins; D016193:G1 Phase / Q000502:physiology / Q000528:radiation effects; D006367:HeLa Cells; D006801:Humans; D009687:Nuclear Proteins; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011836:Radiation Tolerance / Q000502:physiology*; D016196:S Phase / Q000502:physiology / Q000528:radiation effects; D012694:Serine / Q000737:chemistry; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000737:chemistry / Q000378:metabolism / Q000528:radiation effects; D025521:Tumor Suppressor Proteins; D000077191:Wortmannin
D000730:Androstadienes; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D012694:Serine; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D017346:Protein Serine-Threonine Kinases; D000077191:Wortmannin