Yield of single- and double-strand breaks and nucleobase lesions in fully hydrated plasmid DNA films irradiated with high-LET charged particles

高LET荷電粒子により高水和状態のプラスミドDNA中に誘発される1本鎖切断,2本鎖切断及び塩基損傷の収率

牛込 剛史*; 鹿園 直哉; 藤井 健太郎; 渡辺 立子; 鈴木 雅雄*; 鶴岡 千鶴*; 田内 広*; 横谷 明徳

Ushigome, Takeshi*; Shikazono, Naoya; Fujii, Kentaro; Watanabe, Ritsuko; Suzuki, Masao*; Tsuruoka, Chizuru*; Tauchi, Hiroshi*; Yokoya, Akinari

イオンビーム照射したDNA損傷のLET依存性を明らかにするため、水和DNAフィルム中に誘発されるDNA損傷収率を調べた。1本鎖切断収率はHe, C及びNeイオンのLETの増加とともに減少したのに対して、2本鎖切断収率は増加した。照射DNAフィルムを塩基除去修復酵素で処理すると、酵素の作用により鎖切断が生じたことから照射により水和DNAフィルム中にも塩基損傷が生じることがわかった。しかしその収率はLETの増加とともに顕著に現象したことから、高LETほど難修復性の複雑なDNA損傷を誘発することが推測された。

The yield of DNA damage produced in fully hydrated plasmid DNA films has been investigated to determine the linear energy transfer (LET) dependence of damage induction. The yield of single strand breaks (SSBs) with increasing LET levels of He, C and Ne ions. On the other hand, the yields of prompt double strand breaks (DSBs) increased with increasing LET. SSBs were additionally induced by treatment with base excision repair proteins, glycosylases, indicating that base lesions are produced in the hydrated DNA. This result shows that nucleobase lesions are produced via both chemical reactions with diffusible water radicals and direct energy deposition onto DNA or the hydrated layer. The yield of SSBs or DSBs observed by enzymatic treatment notably decreased with increasing LET. These results indicated that higher LET ions preferentially produce a complex type of damage that might compromise the activities of the proteins used in this study.