title: Chemical structure and properties of interstrand cross-links formed by reaction of guanine residues with abasic sites in duplex DNA.
abstract: A new type of interstrand cross-link resulting from the reaction of a DNA abasic site with a guanine residue on the opposing strand of the double helix was recently identified, but the chemical connectivity of the cross-link was not rigorously established. The work described here was designed to characterize the chemical structure and properties of dG-AP cross-links generated in duplex DNA. The approach involved characterization of the nucleoside cross-link "remnant" released by enzymatic digestion of DNA duplexes containing the dG-AP cross-link. We first carried out a chemical synthesis and complete spectroscopic structure determination of the putative cross-link remnant 9b composed of a 2-deoxyribose adduct attached to the exocyclic N(2)-amino group of dG. A reduced analogue of the cross-link remnant was also prepared (11b). Liquid chromatography-tandem mass spectrometric (LC-MS/MS) analysis revealed that the retention times and mass spectral properties of synthetic standards 9b and 11b matched those of the authentic cross-link remnants released by enzymatic digestion of duplexes containing the native and reduced dG-AP cross-link, respectively. These results establish the chemical connectivity of the dG-AP cross-link released from duplex DNA and provide a foundation for detection of this lesion in biological samples. The dG-AP cross-link in duplex DNA was remarkably stable, decomposing with a half-life of 22 days at pH 7 and 23 °C. The intrinsic chemical stability of the dG-AP cross-link suggests that this lesion in duplex DNA may have the power to block DNA-processing enzymes involved in transcription and replication.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Catalano
authors.affiliation: ‡Environmental Toxicology Graduate Program and Department of Chemistry, University of California-Riverside, Riverside, California 92521-0403, United States.
authors.forename: Shuo
authors.initials: S
authors.lastname: Liu
authors.affiliation: ‡Environmental Toxicology Graduate Program and Department of Chemistry, University of California-Riverside, Riverside, California 92521-0403, United States.
authors.forename: Nisana
authors.initials: N
authors.lastname: Andersen
authors.forename: Zhiyu
authors.initials: Z
authors.lastname: Yang
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Johnson
authors.forename: Nathan E
authors.initials: NE
authors.lastname: Price
authors.affiliation: ‡Environmental Toxicology Graduate Program and Department of Chemistry, University of California-Riverside, Riverside, California 92521-0403, United States.
authors.forename: Yinsheng
authors.initials: Y
authors.lastname: Wang
authors.forename: Kent S
authors.initials: KS
authors.lastname: Gates
mesh_terms: D004247:DNA / Q000737:chemistry*; D006147:Guanine / Q000737:chemistry*; D006860:Hydrogen Bonding; D009690:Nucleic Acid Conformation
chemical_list: D006147:Guanine; D004247:DNA