title: Characterization of a novel 8-oxoguanine-DNA glycosylase activity in Escherichia coli and identification of the enzyme as endonuclease VIII.
abstract: 8-Oxoguanine (G*), induced by reactive oxygen species, is mutagenic because it mispairs with A. The major G*-DNA glycosylase (OGG), namely, OGG1 in eukaryotes, or MutM in Escherichia coli, excises G* when paired in DNA with C, G, and T, but not A, presumably because removal of G* from a G*.A pair would be mutagenic. However, repair of G* will prevent mutation when it is incorporated in the nascent strand opposite A. This could be carried out by a second OGG, OGG2, identified in yeast and human cells. We have characterized a new OGG activity in E. coli and then identified it to be endonuclease VIII (Nei), discovered as a damaged pyrimidine-specific DNA glycosylase. Nei shares sequence homology and reaction mechanism with MutM and is similar to human OGG2 in being able to excise G* when paired with A (or G). Kinetic analysis of wild type Nei showed that it has significant activity for excising G* relative to dihydrouracil. The presence of OGG2 type enzyme in both E. coli and eukaryotes, which is at least as efficient in excising G* from a G*.A (or G) pair as from a G*.C pair, supports the possibility of G* repair in the nascent DNA strand.
authors.affiliation: Sealy Center for Molecular Science and Department of Human Biological Chemistry and Genetics, University of Texas Medical Branch, Galveston, Texas 77555, USA.
authors.forename: T K
authors.initials: TK
authors.lastname: Hazra
authors.forename: T
authors.initials: T
authors.lastname: Izumi
authors.forename: R
authors.initials: R
authors.lastname: Venkataraman
authors.forename: Y W
authors.initials: YW
authors.lastname: Kow
authors.forename: M
authors.initials: M
authors.lastname: Dizdaroglu
authors.forename: S
authors.initials: S
authors.lastname: Mitra
mesh_terms: D004249:DNA Damage; D004260:DNA Repair; D043382:DNA-Formamidopyrimidine Glycosylase; D043224:Deoxyribonuclease (Pyrimidine Dimer); D004706:Endodeoxyribonucleases / Q000235:genetics* / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D029968:Escherichia coli Proteins; D006801:Humans; D007700:Kinetics; D009699:N-Glycosyl Hydrolases / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D013379:Substrate Specificity
chemical_list: D029968:Escherichia coli Proteins; D009838:Oligodeoxyribonucleotides; D011994:Recombinant Proteins; D004706:Endodeoxyribonucleases; D043224:Deoxyribonuclease (Pyrimidine Dimer); D009699:N-Glycosyl Hydrolases; D043382:DNA-Formamidopyrimidine Glycosylase; C468610:DNA-formamidopyrimidine glycosylase, E coli