title: Mutagenesis and carcinogenesis caused by the oxidation of nucleic acids.
abstract: Genomes and their precursor nucleotides are highly exposed to reactive oxygen species, which are generated both as byproducts of oxygen respiration or molecular executors in the host defense, and by environmental exposure to ionizing radiation and chemicals. To counteract such oxidative damage in nucleic acids, mammalian cells are equipped with three distinct enzymes. MTH1 protein hydrolyzes oxidized purine nucleoside triphosphates, such as 8-oxo-2'-deoxyguanosine triphosphate and 2-hydroxy-2'-deoxyadenosine triphosphate (2-OH-dATP), to the corresponding monophosphates. We observed increased susceptibility to spontaneous carcinogenesis in MTH1-null mice, which exhibit an increased occurrence of A:T-->C:G and G:C-->T:A transversion mutations. 8-Oxoguanine (8-oxoG) DNA glycosylase, encoded by the OGG1 gene, and adenine DNA glycosylase, encoded by the MUTYH gene, are responsible for the suppression of G:C to T:A transversions caused by the accumulation of 8-oxoG in the genome. Deficiency of these enzymes leads to increased tumorigenesis in the lung and intestinal tract in mice, respectively. MUTYH deficiency may also increase G:C to T:A transversions through the misincorporation of 2-OH-dATP, especially in the intestinal tract, since MUTYH can excise 2-hydroxyadenine opposite guanine in genomic DNA and the repair activity is selectively impaired by a mutation found in patients with autosomal recessive colorectal adenomatous polyposis.
authors.affiliation: Division of Neurofunctional Genomics, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-Ku, Fukuoka, 812-8582, Japan. yusaku@bioreg.kyushu-u.ac.jp
authors.forename: Yusaku
authors.initials: Y
authors.lastname: Nakabeppu
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Sakumi
authors.forename: Katsumi
authors.initials: K
authors.lastname: Sakamoto
authors.forename: Daisuke
authors.initials: D
authors.lastname: Tsuchimoto
authors.forename: Teruhisa
authors.initials: T
authors.lastname: Tsuzuki
authors.forename: Yoshimichi
authors.initials: Y
authors.lastname: Nakatsu
mesh_terms: D000818:Animals; D004249:DNA Damage; D045647:DNA Glycosylases / Q000378:metabolism; D045643:DNA Repair Enzymes / Q000378:metabolism; D006147:Guanine / Q000378:metabolism; D007414:Intestinal Neoplasms / Q000235:genetics / Q000378:metabolism; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism; D051379:Mice; D016296:Mutagenesis; D009154:Mutation; D009369:Neoplasms / Q000235:genetics*; D009696:Nucleic Acids / Q000737:chemistry* / Q000378:metabolism*; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D012878:Skin Neoplasms / Q000235:genetics / Q000378:metabolism; D014466:Ultraviolet Rays / Q000009:adverse effects
chemical_list: D009696:Nucleic Acids; D006147:Guanine; C008183:isoguanine; D010744:Phosphoric Monoester Hydrolases; D045647:DNA Glycosylases; C061738:mutY adenine glycosylase; C479058:oxoguanine glycosylase 1, human; C078207:8-oxodGTPase; D045643:DNA Repair Enzymes