title: DNA sequence context effects on the glycosylase activity of human 8-oxoguanine DNA glycosylase.
abstract: Human 8-oxoguanine DNA glycosylase (OGG1) is a key enzyme involved in removing 7,8-dihydro-8-oxoguanine (8-oxoG), a highly mutagenic DNA lesion generated by oxidative stress. The removal of 8-oxoG by OGG1 is affected by the local DNA sequence, and this feature most likely contributes to observed mutational hot spots in genomic DNA. To elucidate the influence of local DNA sequence on 8-oxoG excision activity of OGG1, we conducted steady-state, pre-steady-state, and single turnover kinetic evaluation of OGG1 in alternate DNA sequence contexts. The sequence context effect was studied for a mutational hot spot at a CpG dinucleotide. Altering either the global DNA sequence or the 5'-flanking unmodified base pair failed to influence the excision of 8-oxoG. Methylation of the cytosine 5' to 8-oxoG also did not affect 8-oxoG excision. In contrast, a 5'-neighboring mismatch strongly decreased the rate of 8-oxoG base removal. Substituting the 5'-C in the CpG dinucleotide with T, A, or tetrahydrofuran (i.e. T:G, A:G, and tetrahydrofuran:G mispairs) resulted in a 10-, 13-, and 4-fold decrease in the rate constant for 8-oxoG excision, respectively. A greater loss in activity was observed when T:C or A:C was positioned 5' of 8-oxoG (59- and 108-fold, respectively). These results indicate that neighboring structural abnormalities 5' to 8-oxoG deter its repair thereby enhancing its mutagenic potential.
authors.affiliation: Laboratory of Structural Biology, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA.
authors.forename: Akira
authors.initials: A
authors.lastname: Sassa
authors.forename: William A
authors.initials: WA
authors.lastname: Beard
authors.forename: Rajendra
authors.initials: R
authors.lastname: Prasad
authors.forename: Samuel H
authors.initials: SH
authors.lastname: Wilson
mesh_terms: D020137:Base Pair Mismatch; D020029:Base Pairing; D001483:Base Sequence; D020134:Catalytic Domain; D053837:DNA Cleavage; D045647:DNA Glycosylases / Q000737:chemistry*; D000072481:DNA Ligase ATP; D011088:DNA Ligases / Q000737:chemistry; D019951:DNA Polymerase beta / Q000737:chemistry; D004260:DNA Repair; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000737:chemistry; D006801:Humans; D006868:Hydrolysis; D007700:Kinetics; D009841:Oligonucleotides / Q000737:chemistry; D013379:Substrate Specificity
chemical_list: D009841:Oligonucleotides; D019951:DNA Polymerase beta; D045647:DNA Glycosylases; C479058:oxoguanine glycosylase 1, human; C085108:APEX1 protein, human; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D011088:DNA Ligases; D000072481:DNA Ligase ATP