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内容記述 |
Ionizing radiation-induced locally multiply damaged site in DNA (clustered DNA damage) is considered to be closely related to the biological effects of radiation. However, the precise yield of clustered DNA damage and its complexity (i.e. the number of lesions per damaged site) in vivo need to be determined to better understand the cellular processing of clustered DNA damage and its outcome. Here, a method has been established to evaluate the yield and the complexity of clustered DNA damage in irradiated TK6 cells by atomic force microscopy (AFM). This was achieved by isolating and concentrating the damaged DNA from the chromosomal DNA. We found that ionizing radiation produced a certain fraction of clustered DNA damage in TK6 cells, whereas Fenton's reagents hardly did, highlighting the significance of clustered DNA damage as a signature of ionizing radiation. We observed that high LET Fe-ion beams produced various types of clustered DNA damage with higher complexity consisting of more than 2 lesions, which were quite few in the case of X-rays. Interestingly, an analysis of repair of DNA damage revealed that non-DSB clustered DNA damage was repaired efficiently in TK6 cells after irradiation of either X-rays or Fe-ion beams. We further found that the repair efficiency of complex DSBs produced by Fe-ion beams was much lower than that generated by X-rays. In this presentation, we will delve into the repair kinetics of each type of DNA damage and elucidate the repair mechanisms involved in complex DNA damage in cells with impaired repair capabilities. |
