Abstract
Ionizing radiation (IR) induces DNA doublestrand breaks(dsb), which are the major cause of the detrimental effects of radiation. DNA dsb activate checkpoint protein, that is ataxia telangiectasia mutated (ATM) kinase is triggered by its autophosphorylation at serine 1981, and phosphorylated ATM protein forms focus. And alsop53 binding-protein 1 (53BP1) was reported to form foci at DNA dsb, whose foci were colocalized with phosphorylated ATM foci. To investigate the dosedependency of induction of DNA dsb with low doses of X-ray, we examined the number and morphology of foci of phosphorylated ATM and 53BP1 induced by X-rays with doses between 1cGy and 100cGy using an immunofluorescence method. As expected, the number of foci of phosphorylated ATM and 53BP1 were found to be induced dose-dependently. In addition, the morphology of the foci were induced by both 1cGy and 100cGy were similar, indicating that DNA double strand breaks induced by low dose ionizing radiation are not qualitatively different from those by higher doses of radiation.
