Abstract
We studied the localization of phosphorylated H2AX (γ-H2AX) in cultured human fibroblasts (NB1RGB) and GFP-tagged rad51 in Chinese hamster CHO cells after irradiation with heavy ion beams. Asynchronous cells were irradiated with X-rays, carbon ion beam (LET is about 30 or 88 keV/μm), Si ion beam (220 keV/μm), Ar (95 keV/μm) and Fe ion beam (440 keV/μm) at room temperature. Gamma-H2AX in irradiated cells was detecteded by immuno-staining from 0 to 24 h after irradiation. Gamma-H2AX monitored by using flow cytometry increased just after irradiation of each radiation and reached maximum around 30 min. Gamma-H2AX was then decreased quickly for cells irradiated with X-rays but presented longer for Si and Fe beams. Induction of γ-H2AX was similar between Si and Fe beams and bigger than X-rays. Under the confocal microscopy, foci of γ-H2AX on cell nucli was not visible just after X-irradiation, but obvious after Fe ion irradiation. In contrast to the data obtained by flowcytometry, induction of foci per nucleus was similar for all the radiations tested at 30 min after irradiation. On the other hand, rad51 accumulation was observed about 1 h after irradiation. Foci of rad51 were visible about 10 h after irradiation both for heavy ions and X-rays.
