title: Independent generation of 5-(2'-deoxycytidinyl)methyl radical and the formation of a novel cross-link lesion between 5-methylcytosine and guanine.
abstract: Reactive oxygen species (ROS) can damage DNA. Although a number of single nucleobase lesions induced by ROS have been structurally characterized, only a few intrastrand cross-link lesions have been identified and characterized, and all of them involve adjacent thymine and guanine or adenine. In mammalian cells, the cytosines at CpG sites are methylated. On the basis of the similar reactivity of 5-methylcytosine and thymine toward hydroxyl radical and the similar orientation of adjacent thymine guanine (TG) and 5-methylcytosine guanine (mCG) in B-DNA, we predict that the cross-link lesion, which was identified in TG and has a covalent bond formed between the 5-methyl carbon atom of T and the C8 carbon atom of G, should also form at mCG site. Here, we report for the first time the independent generation of 5-(2'-deoxycytidinyl)methyl radical, and our results demonstrate that this radical can give rise to the predicted novel intrastrand cross-link lesion in dinucleoside monophosphates d(mCG) and d(GmC). Furthermore, we show that the cross-link lesion can also form in d(mCG) from gamma irradiation under anaerobic conditions.
authors.affiliation: Department of Chemistry-027, University of California at Riverside, Riverside, California 92521-0403, USA.
authors.forename: Qibin
authors.initials: Q
authors.lastname: Zhang
authors.forename: Yinsheng
authors.initials: Y
authors.lastname: Wang
mesh_terms: D044503:5-Methylcytosine / Q000737:chemistry* / Q000378:metabolism; D000693:Anaerobiosis; D002851:Chromatography, High Pressure Liquid; D004247:DNA / Q000737:chemistry / Q000378:metabolism / Q000528:radiation effects; D004249:DNA Damage; D003857:Deoxyuridine / Q000031:analogs & derivatives / Q000138:chemical synthesis; D005609:Free Radicals / Q000737:chemistry / Q000378:metabolism; D005720:Gamma Rays; D006147:Guanine / Q000737:chemistry* / Q000378:metabolism; D009711:Nucleotides / Q000737:chemistry / Q000378:metabolism; D009943:Organophosphorus Compounds / Q000138:chemical synthesis / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D005609:Free Radicals; D009711:Nucleotides; D009943:Organophosphorus Compounds; C434331:phosphoramidite; D006147:Guanine; D044503:5-Methylcytosine; D004247:DNA; D003857:Deoxyuridine