Order effect of repair processes to clustered DNA damage

クラスターDNA損傷修復の修復機序

白石 伊世; 鈴木 雅雄*; 鹿園 直哉; 藤井 健太郎; 横谷 明徳

Shiraishi, Iyo; Suzuki, Masao*; Shikazono, Naoya; Fujii, Kentaro; Yokoya, Akinari

In a living cell, cluster DNA damage is thought to be processed by several different pathways simultaneously or sequentially. Under this situation the cellular response to cluster DNA might depend on the order of repair processes because the configuration of the lesions will be modified by the reaction of initial repair protein, affecting the DNA-binding or excision activities of latter proteins. In the present study, we investigate whether initial enzymatic repair affects latter processes. Plasmid DNA exposed to C ion is treated with two base excision repair enzymes, Nth and Fpg, which convert pyrimidine and purine lesions to a SSB, respectively. Obtained results show that the amount of enzymatically induced SSB is very slightly less in DNA sample treated with Nth first and then Fpg than that of other treatments. These results indicate that the configuration-change of the cluster by the first enzymatic treatment does not significantly influence the activity of secondary enzyme.