Ionizing radiation-induced XRCC4 phosphorylation is mediated through ATM in addition to DNA-PK.
XRCC4 (X-ray cross-complementation group 4) is a protein associated with DNA ligase IV, which is thought to join two DNA ends at the final step of DNA double-strand break repair through non-homologous end-joining. It has been shown that, in response to irradiation or treatment with DNA damaging agents, XRCC4 undergoes phosphorylation, requiring DNA-PK. Here we explored possible role of ATM, which is structurally related to DNA-PK, in the regulation of XRCC4. The radiosensitizing effects of DNA-PK inhibitor and/or ATM inhibitor were dependent on XRCC4. DNA-PK inhibitor and ATM inhibitor did not affect the ionizing radiation-induced chromatin recruitment of XRCC4. Ionizing radiation-induced phosphorylation of XRCC4 in the chromatin-bound fraction was largely inhibited by DNA-PK inhibitor but further diminished by the combination with ATM inhibitor. The present results indicated that XRCC4 phosphorylation is mediated through ATM as well as DNA-PK, although DNA-PK plays the major role. We would propose a possible model that DNA-PK and ATM acts in parallel upstream of XRCC4, regulating through phosphorylation.
Research Laboratory for Nuclear Reactors and Department of Nuclear Engineering, Graduate School of Science and Engineering, Tokyo Institute of Technology.
Shoji
S
Imamichi
Mukesh Kumar
MK
Sharma
Radhika Pankaj
RP
Kamdar
Mikoto
M
Fukuchi
Yoshihisa
Y
Matsumoto
D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins / Q000378:metabolism; D001665:Binding Sites; D045744:Cell Line, Tumor; D002470:Cell Survival; D002843:Chromatin / Q000378:metabolism; D004247:DNA / Q000528:radiation effects*; D053903:DNA Breaks, Double-Stranded; D004249:DNA Damage; D004260:DNA Repair; D051747:DNA-Activated Protein Kinase / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000378:metabolism; D051379:Mice; D009687:Nuclear Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011839:Radiation, Ionizing
D002843:Chromatin; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D009687:Nuclear Proteins; C511788:XRCC4 protein, mouse; D004247:DNA; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; D051747:DNA-Activated Protein Kinase; C497264:Prkdc protein, mouse