title: Quantification of oxidative single-base and intrastrand cross-link lesions in unmethylated and CpG-methylated DNA induced by Fenton-type reagents.
abstract: Methylation of cytosine at CpG sites in mammalian cells plays an important role in the epigenetic regulation of gene expression. Here, we assessed the formation of single-nucleobase lesions and intrastrand cross-link lesions (i.e. G[8-5]C, C[5-8]G, mC[5m-8]G, and G[8-5m]mC, where 'mC' represents 5-methylcytosine) in unmethylated and the corresponding CpG-methylated synthetic double-stranded DNA upon treatment with Fenton-type reagents [i.e. H2O2, ascorbate together with Cu(II) or Fe(II)]. Our results showed that the yields of oxidative single-nucleobase lesions were considerably higher than those of the intrastrand cross-link lesions. Although no significant differences were found for the yields of single-base lesions induced from cytosine and mC, the G[8-5m]mC cross-link was induced approximately 10 times more efficiently than the G[8-5]C cross-link. In addition, the mC[5m-8]G was induced at a level that was approximately 15 times less than G[8-5m]mC, whereas the corresponding C[5-8]G intrastrand cross-link lesion was not detectable. Moreover, Cu(II) is approximately 10-fold as effective as Fe(II) in inducing oxidative DNA lesions. These results suggest that oxidative intrastrand cross-link lesions formed at methylated-CpG sites may account for the previously reported mCG-->TT tandem double mutations induced by Fenton-type reagents.
authors.affiliation: Department of Chemistry-027, University of California, Riverside, CA 92521-0403, USA.
authors.forename: Huachuan
authors.initials: H
authors.lastname: Cao
authors.forename: Yinsheng
authors.initials: Y
authors.lastname: Wang
mesh_terms: D001205:Ascorbic Acid / Q000737:chemistry*; D002853:Chromatography, Liquid; D003300:Copper / Q000737:chemistry*; D018899:CpG Islands; D004249:DNA Damage; D019175:DNA Methylation; D003841:Deoxycytidine / Q000031:analogs & derivatives / Q000737:chemistry; D004121:Dimethyl Sulfoxide / Q000737:chemistry; D016166:Free Radical Scavengers / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D010084:Oxidation-Reduction; D053719:Tandem Mass Spectrometry
chemical_list: C045076:Fenton's reagent; D016166:Free Radical Scavengers; D009838:Oligodeoxyribonucleotides; D003841:Deoxycytidine; D003300:Copper; C016569:5-methyldeoxycytidine; D006861:Hydrogen Peroxide; D007501:Iron; D001205:Ascorbic Acid; D004121:Dimethyl Sulfoxide