title: Examination of hypochlorous acid-induced damage to cytosine residues in a CpG dinucleotide in DNA.
abstract: Inflammation-mediated, neutrophil-derived hypochlorous acid can damage DNA and result in the chlorination damage products 5-chlorocytosine and 5-chlorouracil as well as the oxidation damage products 5-hydroxycytosine and 5-hydroxyuracil. While 5-chlorocytosine could potentially perturb epigenetic signals if formed at a CpG dinucleotide, the remaining products are miscoding and could result in transition mutations. In this article, we have investigated the reaction of hypochlorous acid with an oligonucleotide site-specifically enriched with 15N to probe the reactivity of cytosine at CpG. These experiments demonstrate directly the formation of 5-chlorocytosine at a CpG dinucleotide in duplex DNA. We observe that chlorination relative to oxidation damage is greater at CpG by a factor of approximately two, whereas similar amounts of 5-chlorocytosine and 5-hydroxycytosine are formed at two non-CpG sites examined. The relative amounts of deamination of the cytosine to uracil derivatives are similar at CpG and non-CpG sites. Overall, we observe that the reactivity of cytosine at CpG and non-CpG sites toward hypochlorous acid induced damage is similar (5-chlorocytosine > 5-hydroxycytosine > 5-hydroxyuracil > 5-chlorouracil), with a greater proportion of chlorination damage at CpG sites. These results are in accord with the potential of inflammation-mediated DNA damage to both induce transition mutations and to perturb epigenetic signals.
authors.affiliation: Department of Basic Science, Loma Linda University School of Medicine, Loma Linda, California 92350, USA.
authors.forename: Joseph I
authors.initials: JI
authors.lastname: Kang
authors.forename: Lawrence C
authors.initials: LC
authors.lastname: Sowers
mesh_terms: D018899:CpG Islands; D003545:Cysteine / Q000737:chemistry / Q000378:metabolism; D004247:DNA / Q000737:chemistry* / Q000378:metabolism*; D006997:Hypochlorous Acid / Q000633:toxicity*; D013058:Mass Spectrometry; D009711:Nucleotides / Q000737:chemistry* / Q000378:metabolism*; D010084:Oxidation-Reduction / Q000187:drug effects; D044366:Transition Temperature
chemical_list: D009711:Nucleotides; D006997:Hypochlorous Acid; D004247:DNA; D003545:Cysteine