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内容記述 |
Radiation-induced locally multiply damaged site in DNA (clustered DNA damage) is thought to be closely related to the biological effects of radiation. A method has been established to evaluate the complexity of clustered DNA damage (i.e. the number of lesions per damaged site) in genomic DNA extracted from TK6 cells irradiated with a low-dose ionizing radiation by atomic force microscopy (AFM). This was realized by isolating and concentrating the DNA molecules with lesions from the whole irradiated DNA molecules also containing intact ones. The purpose of this study is to estimate the level of damage clustering in vivo. We found that ionizing radiation (X-rays and Fe-ion beams) produced clustered DNA damage in TK6 cells, whereas Fenton's reagents did not find it in Fenton’s regent-treated DNA, highlighting the importance of clustered DNA damage as a signature of ionizing radiation. We further observed that Fe-ion beams (high-LET radiation) 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. Surprisingly, analyses of repair of DNA damage revealed that non-DSB clustered DNA damage were repaired efficiently in TK6 cells after irradiation of either X-rays and Fe-ion beams. The repair efficiency of complex DSBs, which were frequently produced after Fe-ion beams, were low. |
