title: Evidence for two DNA repair enzymes for 8-hydroxyguanine (7,8-dihydro-8-oxoguanine) in human cells.
abstract: Two DNA repair enzymes for 8-hydroxyguanine (also known as 7,8-dihydro-8-oxoguanine; OH8Gua, oxo8Gua) have been identified in human HeLa cell nuclear extract. One is OH8Gua-glycosylase and the other is OH8Gua-endonuclease that lacks OH8Gua-glycosylase activity. They were separated by heparin-Sepharose column chromatography and characterized by endonuclease nicking assay or by measuring the OH8Gua released from substrate DNA using high pressure liquid chromatography-electrochemical detection. Both OH8Gua repair enzymes act only on the OH8Gua-containing strand of the duplex substrate DNA containing OH8Gua/C, OH8Gua/T, or OH8Gua/G. DNA containing OH8Gua/A base pair was very poor substrate for either enzymes. OH8Gua-endonuclease simultaneously cleaves phosphodiester bonds on both sides of the OH8Gua residue, leaving 5'-hydroxy and 3'-hydroxy groups.
authors.affiliation: Banyu Tsukuba Research Institute, Merck Research Laboratories, Ibaraki, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Bessho
authors.forename: K
authors.initials: K
authors.lastname: Tano
authors.forename: H
authors.initials: H
authors.lastname: Kasai
authors.forename: E
authors.initials: E
authors.lastname: Ohtsuka
authors.forename: S
authors.initials: S
authors.lastname: Nishimura
mesh_terms: D001483:Base Sequence; D002467:Cell Nucleus / Q000201:enzymology*; D002846:Chromatography, Affinity; D002851:Chromatography, High Pressure Liquid; D004260:DNA Repair; D043382:DNA-Formamidopyrimidine Glycosylase; D006147:Guanine / Q000031:analogs & derivatives* / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D009699:N-Glycosyl Hydrolases / Q000302:isolation & purification / Q000378:metabolism*; D009838:Oligodeoxyribonucleotides; D013379:Substrate Specificity
chemical_list: D009838:Oligodeoxyribonucleotides; C024829:8-hydroxyguanine; D006147:Guanine; D009699:N-Glycosyl Hydrolases; D043382:DNA-Formamidopyrimidine Glycosylase