title: Mammalian 8-oxoguanine DNA glycosylase 1 incises 8-oxoadenine opposite cytosine in nuclei and mitochondria, while a different glycosylase incises 8-oxoadenine opposite guanine in nuclei.
abstract: Cells are continuously exposed to oxidative species, which cause several types of oxidative DNA lesions. Repair of some of these lesions has been well characterized but little is known about the repair of many DNA lesions. The oxidized adenine base, 7,8-dihydro-8-oxoadenine (8-oxoA), is a relatively common DNA lesion, which is believed to be mutagenic in mammalian cells. This study investigates repair of 8-oxoA in nuclear and mitochondrial mammalian extracts. In nuclei, 8-oxoA:C and 8-oxoA:G base pairs are recognized and cleaved; in contrast, only 8-oxoA:C base pairs are cleaved in mitochondria. High stability of the DNA helix increased the efficiency of incision of 8-oxoA, and the efficiency decreased at DNA bends and condensed regions of the helix. Using liver extracts from mice knocked out for 8-oxoguanine DNA glycosylase 1 (OGG1), we demonstrated that OGG1 is the only glycosylase that incises 8-oxoA, when base-paired with cytosine in mitochondria and nuclei, but a different enzyme incises 8-oxoA when base-paired with guanine in the nucleus. Consistent with this result, a covalent DNA-protein complex was trapped using purified human OGG1 or human nuclear or mitochondrial extracts with a DNA substrate containing an 8-oxoA:C base pair.
authors.affiliation: Danish Center for Molecular Gerontology, Department of Molecular Biology, University of Aarhus, DK-8000 Aarhus C, Denmark.
authors.forename: Anne
authors.initials: A
authors.lastname: Jensen
authors.forename: Guillaume
authors.initials: G
authors.lastname: Calvayrac
authors.forename: Bensu
authors.initials: B
authors.lastname: Karahalil
authors.forename: Vilhelm A
authors.initials: VA
authors.lastname: Bohr
authors.forename: Tinna
authors.initials: T
authors.lastname: Stevnsner
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D020029:Base Pairing; D001483:Base Sequence; D002461:Cell Line, Transformed; D002467:Cell Nucleus / Q000201:enzymology*; D003596:Cytosine; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D004260:DNA Repair; D043382:DNA-Formamidopyrimidine Glycosylase; D005347:Fibroblasts / Q000201:enzymology / Q000648:ultrastructure; D006147:Guanine; D006801:Humans; D008099:Liver / Q000201:enzymology; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008928:Mitochondria / Q000201:enzymology*; D009699:N-Glycosyl Hydrolases / Q000172:deficiency / Q000378:metabolism*; D009690:Nucleic Acid Conformation; D009841:Oligonucleotides / Q000737:chemistry / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D009841:Oligonucleotides; C002992:8-hydroxyadenine; D006147:Guanine; D003596:Cytosine; D004247:DNA; D009699:N-Glycosyl Hydrolases; D043382:DNA-Formamidopyrimidine Glycosylase; D008274:Magnesium; D000225:Adenine