title: Base excision repair of adenine/8-oxoguanine mispairs by an aphidicolin-sensitive DNA polymerase in human cell extracts.
abstract: Replication of DNA containing 8-oxo-7,8-dihydroguanine (8oxoG) can generate 8oxoG/A base pairs which, if uncorrected, lead to G-->T transversions. It is generally accepted that the repair of these promutagenic base pairs in human cells is initiated by the MutY DNA glycosylase homolog (hMYH). Here we provide biochemical evidence that human cell extracts perform base excision repair (BER) on both DNA strands of an 8oxoG/A mismatch. At early repair times the specificity of nucleotide incorporation indicates a preferential insertion of C opposite 8oxoG leading to the formation of 8oxoG/C pairs. This is followed by repair synthesis on the opposite DNA strand that is consistent with hOGG1-mediated correction of 8oxoG/C to G/C. Repair synthesis on either strand is completely inhibited by aphidicolin suggesting that a replicative DNA polymerase is involved in the gap filling. This is the first demonstration that repair of 8oxoG/A base pairs is by two BER events likely mediated by Poldelta/epsilon. We suggest that the Poldelta/epsilon-mediated BER is the general mode of repair when BER lesions are formed at replication forks.
authors.affiliation: Laboratory of Comparative Toxicology and Ecotoxicology, Istituto Superiore di Sanita', Viale Regina Elena 299, 00161 Rome, Italy.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Parlanti
authors.forename: Paola
authors.initials: P
authors.lastname: Fortini
authors.forename: Peter
authors.initials: P
authors.lastname: Macpherson
authors.forename: Jacques
authors.initials: J
authors.lastname: Laval
authors.forename: Eugenia
authors.initials: E
authors.lastname: Dogliotti
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives* / Q000378:metabolism*; D016590:Aphidicolin / Q000494:pharmacology*; D020137:Base Pair Mismatch / Q000235:genetics; D020029:Base Pairing / Q000235:genetics*; D002457:Cell Extracts; D004247:DNA / Q000378:metabolism*; D017931:DNA Primers / Q000737:chemistry; D004260:DNA Repair; D004351:Drug Resistance; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006147:Guanine / Q000031:analogs & derivatives* / Q000378:metabolism*; D006367:HeLa Cells / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D019384:Nucleic Acid Synthesis Inhibitors
chemical_list: D002457:Cell Extracts; D017931:DNA Primers; D004791:Enzyme Inhibitors; D019384:Nucleic Acid Synthesis Inhibitors; C002992:8-hydroxyadenine; D016590:Aphidicolin; C024829:8-hydroxyguanine; D006147:Guanine; D004247:DNA; D000225:Adenine