title: Repair of 3-methylthymine and 1-methylguanine lesions by bacterial and human AlkB proteins.
abstract: The Escherichia coli AlkB protein repairs 1-methyladenine (1-meA) and 3-methylcytosine (3-meC) lesions in DNA and RNA by oxidative demethylation, a reaction requiring ferrous iron and 2-oxoglutarate as cofactor and co-substrate, respectively. Here, we have studied the activity of AlkB proteins on 3-methylthymine (3-meT) and 1-methylguanine (1-meG), two minor lesions which are structurally analogous to 1-meA and 3-meC. AlkB as well as the human AlkB homologues, hABH2 and hABH3, were all able to demethylate 3-meT in a DNA oligonucleotide containing a single 3-meT residue. Also, 1-meG lesions introduced by chemical methylation of tRNA were efficiently removed by AlkB. Unlike 1-meA and 3-meC, nucleosides or bases corresponding to 1-meG or 3-meT did not stimulate the uncoupled, AlkB-mediated decarboxylation of 2-oxoglutarate. Our data show that 3-meT and 1-meG are repaired by AlkB, but indicate that the recognition of these substrates is different from that in the case of 1-meA and 3-meC.
authors.affiliation: Department of Molecular Biosciences, University of Oslo, Postboks 1041, Blindern, 0316 Oslo, Norway. pal.falnes@imbv.uio.no
authors.forename: Pål Ø
authors.initials: PØ
authors.lastname: Falnes
mesh_terms: D000071498:AlkB Homolog 1, Histone H2a Dioxygenase; D002851:Chromatography, High Pressure Liquid; D004260:DNA Repair; D045643:DNA Repair Enzymes; D004261:DNA Replication; D003653:Decarboxylation; D029968:Escherichia coli Proteins / Q000378:metabolism*; D006147:Guanine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007656:Ketoglutaric Acids / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D013379:Substrate Specificity; D013941:Thymine / Q000031:analogs & derivatives* / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; D007656:Ketoglutaric Acids; C017515:1-methylguanine; D006147:Guanine; D006899:Mixed Function Oxygenases; C466427:AlkB protein, E coli; C499236:ALKBH1 protein, human; D000071498:AlkB Homolog 1, Histone H2a Dioxygenase; D045643:DNA Repair Enzymes; D013941:Thymine; C002347:3-methylthymine