○Akito Komi1 Taishu Kawada1,2 Hitoki Mitani1 Katsuhito Kino1,31 Dept. of Nano Material and Bio Eng., Faculty of Sci. and Eng., Tokushima Bunri Univ.2 Grad. Sch. of Biomedical and Health Sci., Hiroshima Univ.3 Center for Adv. Sci. and Eng., Tokushima Bunri Univ.Base excision repair of a novel DNA damage by repair enzymesGuanine is the most readily oxidized of the four DNA bases by several oxidants. Imidazolone (Iz) is known as an oxidative guanine damage, and hydrolysis of Iz generates oxazolone (Oz) under in vivo conditions. A previous study showed that Oz was degraded into guanidinoformimine (Gf) (J. Am. Chem. Soc. 2012, 143, 4925). Under the conditions where Gf is generated, we fortuitously found a new product X. Like 8-oxoguanine (8-oxoG), the new product X is stable under basic conditions, under high temperatures and under the presence of piperidine. Moreover, on the complementary strand side of the new product X, guanine was incorporated by DNA polymerases α, δ and ε so that the new product X may cause G-to-C transversions.E.coli formamidoprimidine-DNA glycosylase (Fpg) and endonuclease VIII (Nei) are base excision repair enzymes. We analyzed cleavage activities of Fpg and Nei against the new product X. As results, Fpg cleaved oligomers including X more than those including 8-oxoG. Moreover, Fpg had base selectivity opposite X, although Nei had no such selectivity.Human endonuclease VIII-like 1 (hNEIL1), a homolog of the prokaryotic base excision repair enzyme Fpg/Nei, is involved in the repair of oxidative DNA damages (e.g. 8-oxoG). We analyzed the cleavage activity of Alexa-labeled DNA containing X with hNEIL1. As results, though 1000 fmol/μL hNEIL1 showed selectivity on the complementary strand side of oligomers containing 8-oxoG, 33 fmol/μL hNEIL1 did not have such selectivity for X. 51P 021
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