title: Repair deficient mice reveal mABH2 as the primary oxidative demethylase for repairing 1meA and 3meC lesions in DNA.
abstract: Two human homologs of the Escherichia coli AlkB protein, denoted hABH2 and hABH3, were recently shown to directly reverse 1-methyladenine (1meA) and 3-methylcytosine (3meC) damages in DNA. We demonstrate that mice lacking functional mABH2 or mABH3 genes, or both, are viable and without overt phenotypes. Neither were histopathological changes observed in the gene-targeted mice. However, in the absence of any exogenous exposure to methylating agents, mice lacking mABH2, but not mABH3 defective mice, accumulate significant levels of 1meA in the genome, suggesting the presence of a biologically relevant endogenous source of methylating agent. Furthermore, embryonal fibroblasts from mABH2-deficient mice are unable to remove methyl methane sulfate (MMS)-induced 1meA from genomic DNA and display increased cytotoxicity after MMS exposure. In agreement with these results, we found that in vitro repair of 1meA and 3meC in double-stranded DNA by nuclear extracts depended primarily, if not solely, on mABH2. Our data suggest that mABH2 and mABH3 have different roles in the defense against alkylating agents.
authors.affiliation: Centre for Molecular Biology and Neuroscience and Institute of Medical Microbiology, Rikshospitalet-Radiumhospitalet HF, University of Oslo, Oslo, Norway.
authors.forename: Jeanette
authors.initials: J
authors.lastname: Ringvoll
authors.forename: Line M
authors.initials: LM
authors.lastname: Nordstrand
authors.forename: Cathrine B
authors.initials: CB
authors.lastname: Vågbø
authors.forename: Vivi
authors.initials: V
authors.lastname: Talstad
authors.forename: Karen
authors.initials: K
authors.lastname: Reite
authors.forename: Per Arne
authors.initials: PA
authors.lastname: Aas
authors.forename: Knut H
authors.initials: KH
authors.lastname: Lauritzen
authors.forename: Nina Beate
authors.initials: NB
authors.lastname: Liabakk
authors.forename: Alexandra
authors.initials: A
authors.lastname: Bjørk
authors.forename: Richard William
authors.initials: RW
authors.lastname: Doughty
authors.forename: Pål Ø
authors.initials: PØ
authors.lastname: Falnes
authors.forename: Hans E
authors.initials: HE
authors.lastname: Krokan
authors.forename: Arne
authors.initials: A
authors.lastname: Klungland
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D000071499:AlkB Homolog 2, Alpha-Ketoglutarate-Dependent Dioxygenase; D000071500:AlkB Homolog 3, Alpha-Ketoglutarate-Dependent Dioxygenase; D000483:Alleles; D000818:Animals; D002460:Cell Line; D003596:Cytosine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D004260:DNA Repair; D045643:DNA Repair Enzymes; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D049308:Dioxygenases; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D015394:Molecular Structure; D014018:Tissue Distribution
chemical_list: D004268:DNA-Binding Proteins; C036386:3-methylcytosine; C008407:1-methyladenine; D003596:Cytosine; D004247:DNA; D049308:Dioxygenases; C486439:ALKBH3 protein, human; D000071500:AlkB Homolog 3, Alpha-Ketoglutarate-Dependent Dioxygenase; C486440:ALKBH2 protein, human; D000071499:AlkB Homolog 2, Alpha-Ketoglutarate-Dependent Dioxygenase; C511886:Alkbh2 protein, mouse; D045643:DNA Repair Enzymes; D000225:Adenine