title: Accumulation of adenine DNA glycosylase-sensitive sites in human mitochondrial DNA.
abstract: The mitochondrial respiratory chain inevitably produces reactive oxygen species as byproducts of aerobic ATP synthesis. Mitochondrial DNA (mtDNA), which is located close to the respiratory chain, is reported to contain much more 8-oxoguanine (8-oxoG), an oxidatively modified guanine base, than nuclear DNA. Despite such a high amount of 8-oxoG in mtDNA (1-2 8-oxoG/10(4) G), mtDNA is barely cleaved by an 8-oxoG DNA glycosylase or MutM, which specifically excises 8-oxoG from a C:8-oxoG pair. We find here that about half of human mtDNA molecules are cleaved by another 8-oxoG-recognizing enzyme, an adenine DNA glycosylase or MutY, which excises adenine from an A:8-oxoG pair. The cleavage sites are mapped to adenines. The calculated number of MutY-sensitive sites in mtDNA is approximately 1.4/10(4) G. This value roughly corresponds with the electrochemically measured amount of 8-oxoG in mtDNA (2.2/10(4) G), raising the possibility that 8-oxoG mainly accumulates as an A:8-oxoG pair.
authors.affiliation: Department of Biochemistry, Kyushu University Graduate School of Medical Sciences, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Miyako
authors.forename: C
authors.initials: C
authors.lastname: Takamatsu
authors.forename: S
authors.initials: S
authors.lastname: Umeda
authors.forename: T
authors.initials: T
authors.lastname: Tajiri
authors.forename: M
authors.initials: M
authors.lastname: Furuichi
authors.forename: Y
authors.initials: Y
authors.lastname: Nakabeppu
authors.forename: M
authors.initials: M
authors.lastname: Sekiguchi
authors.forename: N
authors.initials: N
authors.lastname: Hamasaki
authors.forename: K
authors.initials: K
authors.lastname: Takeshige
authors.forename: D
authors.initials: D
authors.lastname: Kang
mesh_terms: D000225:Adenine; D045647:DNA Glycosylases; D004272:DNA, Mitochondrial / Q000378:metabolism*; D043382:DNA-Formamidopyrimidine Glycosylase; D004579:Electron Transport; D006151:Guanosine / Q000031:analogs & derivatives / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D009699:N-Glycosyl Hydrolases / Q000378:metabolism*; D009841:Oligonucleotides / Q000378:metabolism
chemical_list: D004272:DNA, Mitochondrial; D009841:Oligonucleotides; D006151:Guanosine; C046215:8-hydroxyguanosine; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; C061738:mutY adenine glycosylase; D043382:DNA-Formamidopyrimidine Glycosylase; D000225:Adenine