Abstract
To identify the dynamics of DNA damage-recognizing proteins at high LET particles-induced track, we analyzed the focus formation and phosphorylation of these proteins after exposure to iron-ion beams (500 MeV/u, 200 KeV/microm) using immunocytochemistory and flowcytometry. Since the focus formation of phospho-H2AX (gamma H2AX) is well understood to be detected at radiation-induced double strand breaks (DSBs), we performed the visualization of spatial distribution of lesions from an aspect of dose dependency. The number of this track induced by iron-ion beams was well corresponded with the value of a calculation well. Although the phosphorylation of H2AX is increased with dose dependent manner after exposure to Fe-ion beams like X-rays, more gamma H2AX remain in iron-ion beams irradiated cells than in X- irradiated cells. This result suggests that the HZE particles-induced lesions are irreparable. In addition, we demonstrate that DNA damage-recognizing proteins such as phospho-serine 1981 of ATM, phospho-threonine 2609 of DNA-PKcs, phospho-serine 343 of NBS1 and phospho-threonine 68 of Chk2 co-localized with gamma H2AX at high LET-radiation-induced portion. These findings suggest that iron-ion beams were quite effective for detection of DNA damages of DSBs recognized with DNA repair enzymes used here after phosphorylation of them, because iron-ion beams can be used to generate extremely localized at DNA damages within restricted regions of the nuclei.
