Suzuki Keiji, Okada Hiroshi, Yamauchi Motohiro, Oka Yasuyoshi, Kodama Seiji, Watanabe Masami
Division of Radiation Biology, Department of Radiology and Radiation Biology, Course of Life Sciences and Radiation Research, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki 852-8521, Japan.
Radiat Res. 2006 May;165(5):499-504. doi: 10.1667/RR3542.1.
We examined the formation of phosphorylated ataxia telangiectasia mutated (ATM) foci in exponentially growing normal human diploid cells exposed to low doses of X rays. Phosphorylated ATM foci were detected immediately after irradiation, and the number of foci decreased as the time after irradiation increased. The kinetics of phosphorylated ATM foci was comparable to that of phosphorylated histone H2AX. We found that there were fewer spontaneous phosphorylated ATM foci than that phosphorylated histone H2AX foci. Notably, significant numbers of phosphorylated histone H2AX foci, but not phosphorylated ATM foci, were detected in the S-phase cells. The induction of foci showed a linear dose-response relationship with doses ranging for 10 mGy to 1 Gy, and the average number of phosphorylated ATM foci per gray was approximately 50. The average size of the foci was comparable for the cells irradiated with 20 mGy and 1 Gy, and there was no significant difference in the kinetics of disappearance of foci, indicating that DNA double-strand breaks are similarly recognized by DNA damage checkpoints and are repaired irrespective of the dose.
我们检测了处于指数生长期的正常人二倍体细胞在受到低剂量X射线照射后磷酸化共济失调毛细血管扩张突变（ATM）灶的形成情况。照射后立即检测到磷酸化ATM灶，且随着照射后时间的增加，灶的数量减少。磷酸化ATM灶的动力学与磷酸化组蛋白H2AX的动力学相当。我们发现自发磷酸化ATM灶比磷酸化组蛋白H2AX灶少。值得注意的是，在S期细胞中检测到大量磷酸化组蛋白H2AX灶，但未检测到磷酸化ATM灶。灶的诱导在10 mGy至1 Gy的剂量范围内呈现线性剂量反应关系，每格雷的磷酸化ATM灶平均数量约为50个。用20 mGy和1 Gy照射的细胞，灶的平均大小相当，且灶消失的动力学没有显著差异，这表明DNA双链断裂被DNA损伤检查点以类似方式识别并被修复，与剂量无关。
