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 ∼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 ∼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 ∼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.

Comprehensive Assessment of Oxidatively Induced Modifications of DNA in a Rat Model of Human Wilson's Disease

“…3B). This result is seemingly incongruent with our previous in vitro data concerning the dose-dependent induction of 5-HmdC by Fenton-type reagent (30). However, results from our in vitro biochemical assay suggested Aside from TET enzymes, other members of the Fe(II)-and 2-OG-dependent dioxygenase family may also act as potential molecular targets for copper toxicity.…”

“…LEA and LEC rats (14 -16 week old) were bred in a Core Facility at Einstein as described previously (10). The stable isotope-labeled S-cdA, ScdG and 5-HmdC were synthesized previously (10,30). The dA and dG as well as their stable isotope-labeled counterparts were synthesized following procedures published previously (35,36).…”

DNA Sequence Context Effects on the Glycosylase Activity of Human 8-Oxoguanine DNA Glycosylase

“…Several studies suggest that 5-meC may increase the mutagenicity of a neighboring damaged guanine by forming an aberrant base pair adjacent to 8-oxoG creating a tandem DNA lesion (i.e. thymine glycol/8-oxoG or AP-site/8-oxoG), or intra-strand cross-linked DNA damage in the genome (37)(38)(39). The mutagenicity and repair efficiency of 8-oxoG can be strongly affected by the local DNA sequence.…”

Nucleophilic Mechanism of ROS/RNS Signaling in Cancer Epigenetic Modifications

“…Later on it was found that the formed oxygenated products can affect DNA methylation, for example the methylation of cytosines by hydroxyl free radical adducts on adjacent guanine residues [9]. In subsequent works it has been proposed that hydroxyl radicals damage the DNA methyl-CpG sites [10,11].…”