title: Characterization of DNA--protein cross-links induced by oxanine: cellular damage derived from nitric oxide and nitrous acid.
abstract: Reactive nitrogen species are implicated in inflammatory diseases and cancers. Oxanine (Oxa) is a DNA lesion derived from the guanine base with nitric oxide, nitrous acid, or N-nitrosoindoles. It was shown by gel electrophoresis that oxanine mediated the formation of DNA-protein cross-links (DPCs) with DNA-binding proteins and in the cell extract. Although 2'-deoxyoxanosine was shown to react with amines including the N-terminal amino group of glycine, the structures of DNA-protein cross-links induced by oxanine have not been characterized. In this study, we find that the thiol group of the amino acid side chain is reactive toward oxanine, forming a thioester. Two reaction products of oxanine, namely, the thioester and the amide adducts, with the endogenous tripeptide glutathione (GSH) as a model protein were characterized on the basis of their UV, NMR (1H- and 13C-), and mass spectra. Interestingly, the disulfide GSSG also reacts with oxanine, forming the thioester adduct. The thioester and the amide adducts are generated when GSH and GSSG react with oxanine-containing calf thymus DNA, and they might be possible forms of cellular DPCs. Because the repair mechanism of DPCs is not extensively investigated, the characterization of oxanine-derived DPC structures should shed light on their detection in vivo and on their biological consequences.
authors.affiliation: Department of Chemistry and Biochemistry, National Chung Cheng University, 168 University Road, Ming-Hsiung, Chia-Yi 62142, Taiwan. chehjc@ccu.edu.tw
authors.forename: Hauh-Jyun Candy
authors.initials: HJ
authors.lastname: Chen
authors.forename: Chia-Jong
authors.initials: CJ
authors.lastname: Hsieh
authors.forename: Li-Ching
authors.initials: LC
authors.lastname: Shen
authors.forename: Chia-Ming
authors.initials: CM
authors.lastname: Chang
mesh_terms: D002851:Chromatography, High Pressure Liquid; D003432:Cross-Linking Reagents / Q000737:chemistry; D004247:DNA / Q000737:chemistry*; D003853:Deoxyribonucleosides / Q000737:chemistry; D005978:Glutathione / Q000737:chemistry; D019803:Glutathione Disulfide / Q000737:chemistry; D009569:Nitric Oxide / Q000737:chemistry*; D009608:Nitrous Acid / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular; D011506:Proteins / Q000737:chemistry*; D011684:Purine Nucleosides / Q000737:chemistry*; D026361:Reactive Nitrogen Species / Q000737:chemistry*; D053719:Tandem Mass Spectrometry
chemical_list: D003432:Cross-Linking Reagents; D003853:Deoxyribonucleosides; D011506:Proteins; D011684:Purine Nucleosides; D026361:Reactive Nitrogen Species; C468766:oxanine; D009569:Nitric Oxide; C042917:2'-deoxyoxanosine; D004247:DNA; D005978:Glutathione; D009608:Nitrous Acid; D019803:Glutathione Disulfide