title: Novel repair activities of AlkA (3-methyladenine DNA glycosylase II) and endonuclease VIII for xanthine and oxanine, guanine lesions induced by nitric oxide and nitrous acid.
abstract: Nitrosation of guanine in DNA by nitrogen oxides such as nitric oxide (NO) and nitrous acid leads to formation of xanthine (Xan) and oxanine (Oxa), potentially cytotoxic and mutagenic lesions. In the present study, we have examined the repair capacity of DNA N-glycosylases from Escherichia coli for Xan and Oxa. The nicking assay with the defined substrates containing Xan and Oxa revealed that AlkA [in combination with endonuclease (Endo) IV] and Endo VIII recognized Xan in the tested enzymes. The activity (V(max)/K(m)) of AlkA for Xan was 5-fold lower than that for 7-methylguanine, and that of Endo VIII was 50-fold lower than that for thymine glycol. The activity of AlkA and Endo VIII for Xan was further substantiated by the release of [(3)H]Xan from the substrate. The treatment of E.coli with N-methyl-N'-nitro-N-nitrosoguanidine increased the Xan-excising activity in the cell extract from alkA(+) but not alkA(-) strains. The alkA and nei (the Endo VIII gene) double mutant, but not the single mutants, exhibited increased sensitivity to nitrous acid relative to the wild type strain. AlkA and Endo VIII also exhibited excision activity for Oxa, but the activity was much lower than that for Xan.
authors.affiliation: Department of Mathematical and Life Sciences, Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Terato
authors.forename: Aya
authors.initials: A
authors.lastname: Masaoka
authors.forename: Kenjiro
authors.initials: K
authors.lastname: Asagoshi
authors.forename: Akiko
authors.initials: A
authors.lastname: Honsho
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Ohyama
authors.forename: Toshinori
authors.initials: T
authors.lastname: Suzuki
authors.forename: Masaki
authors.initials: M
authors.lastname: Yamada
authors.forename: Keisuke
authors.initials: K
authors.lastname: Makino
authors.forename: Kazuo
authors.initials: K
authors.lastname: Yamamoto
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ide
mesh_terms: D045647:DNA Glycosylases; D004260:DNA Repair; D043224:Deoxyribonuclease (Pyrimidine Dimer); D004706:Endodeoxyribonucleases / Q000378:metabolism*; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D006147:Guanine / Q000737:chemistry / Q000378:metabolism*; D009699:N-Glycosyl Hydrolases / Q000378:metabolism*; D009569:Nitric Oxide / Q000737:chemistry / Q000633:toxicity; D009589:Nitrogen Oxides / Q000633:toxicity*; D009608:Nitrous Acid / Q000737:chemistry / Q000633:toxicity; D009841:Oligonucleotides / Q000737:chemistry; D011684:Purine Nucleosides / Q000737:chemistry / Q000378:metabolism; D019820:Xanthine / Q000737:chemistry / Q000378:metabolism
chemical_list: D009589:Nitrogen Oxides; D009841:Oligonucleotides; D011684:Purine Nucleosides; C468766:oxanine; D019820:Xanthine; D009569:Nitric Oxide; D006147:Guanine; D004706:Endodeoxyribonucleases; D043224:Deoxyribonuclease (Pyrimidine Dimer); D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; C076131:DNA-3-methyladenine glycosidase II; D009608:Nitrous Acid