Oxidation of the sugar moiety of DNA by ionizing radiation or bleomycin could induce the formation of a cluster DNA lesion

Abstract

Bleomycin, a radiomimetic drug currently used in human cancer therapy, is a well known carcinogen. Its toxicity is mostly attributed to its potentiality to induce DNA double strand breaks likely arising from the formation of two vicinal DNA strand breaks, initiated by C4-hydrogen abstraction on the 2-deoxyribose moiety.In this work we demonstrate that such a hydrogen abstraction reaction is able to induce the formation of a clustered DNA lesion, involving a 3 strand break together with a modified sugar residue exhibiting a reactive ␣,␤-unsaturated aldehyde that further reacts with a proximate cytosine base. The lesion thus produced was detected as a mixture of four isomers by HPLC coupled to tandem mass spectrometry subsequent to DNA extraction and enzymatic digestion. The modified nucleosides that constitute new types of cytosine adducts were identified as the likely two pairs of diastereomers of 6-(2-deoxy-␤-Derythro-pentofuranosyl)-2-hydroxy-3(3-hydroxy-2-oxopropyl)-2,6-dihydroimidazo[1,2-c]-pyrimidin-5(3H)-one as inferred from mass spectrometry and NMR analyses of the chemically synthesized nucleosides. We demonstrate that bleomycin, and to a minor extent ionizing radiation, are able to induce significant amounts of the cytosine damage in cellular DNA. In addition, the repair kinetic of the lesion in a human lymphocyte cell line is rather slow, with a half-life of 10 h. The 2 -deoxycytidine adducts thus characterized that represent the first example of complex DNA lesions isolated and identified in cellular DNA upon one radical hit are likely to play an important role in the toxicity of bleomycin.cluster lesions ͉ DNA damage ͉ DNA repair

Rapid DNA–protein cross-linking and strand scission by an abasic site in a nucleosome core particle

“…Kinetic and trapping experiments conducted on nucleosome core particles composed of wild-type or a mutant form of histone H4 lacking its lysine-rich tail (residues [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] show that this portion of the protein contributes to the accelerated cleavage of AP sites in the vicinity of SHL 1.5. Removal of the H4 tail results in only modest reduction in AP site cleavage compared to core particle comprised of wild-type histones.…”

Ultra-performance liquid chromatography–tandem mass spectrometry for rapid and highly sensitive analysis of stereoisomers of benzo[a]pyrene diol epoxide–DNA adducts

“…Because of the improved detection selectivity, it takes shorter time (20-50 min) for the stereoslective separation [21,22,30]. Due to large sample consumption (30-300 g DNA), the LC-MS based methods are often used for identification of new DNA damage and analysis of DNA adducts from cultured cells or animal tissues rather than human biomonitoring [19,31,32].…”

DNA Radiosensitization: The Search for Repair Refractive Lesions Including Double Strand Breaks and Interstrand Crosslinks

“…Several groups have focused on the identification of ICL structures synthesized in model systems using light-and/or oxidationsensitive precursors (Hong et al, 2006;Weng et al, 2007;Peng et al, 2008;Kim & Hong, 2008;Op de Beeck & Madder, 2011). A few structures have been definitively identified in natural conditions and, to our knowledge, only one in cellular DNA (Regulus et al, 2007) (Fig. 6C).…”

“…6C). However, the authors in Regulus et al, (2007) failed to present evidence that this crosslink is exclusively an inter-strand crosslink in cells. Mechanistically, the sole ICL-structure that is exclusively generated with the participation of a primary radiation-induced 5-(2'-deoxyuridinyl) methyl free radical, a product of •OH-induced hydrogen-atom abstraction from thymine, is the T[5m-6n]A crosslink (Ding & Greenberg, 2007;Ding et al, 2008) (Fig.…”