title: DNA interstrand cross-linking upon irradiation of aryl halide C-nucleotides.
abstract: γ-Radiolysis kills cells by damaging DNA via radical processes. Many of the radical pathways are O2 dependent, which results in a reduction in the cytotoxicity of ionizing radiation in hypoxic tumor cells. Consequently, there is a need for chemical agents that increase DNA damage by ionizing radiation under O2-deficient conditions. Modified nucleotides that are incorporated in DNA and produce highly reactive σ-radicals are useful as radiosensitizing agents. Aryl halide C-nucleotides (4-6) were incorporated into oligonucleotides by solid-phase synthesis. Duplex DNA containing 4-6 forms interstrand cross-links upon γ-radiolysis under anaerobic conditions or UV irradiation. Deep Vent (exo(-)) DNA polymerase accepted the nucleotide triphosphate of C-nucleotide 6 as a substrate and preferentially incorporated it opposite pyrimidines, but no further extension was detected. Incorporation of 6 in extended products by Deep Vent (exo(-)) during PCR or by Sequenase during copying of single stranded DNA plasmid was undetectable. Aryl halide nucleotide analogues that produce DNA interstrand cross-links under anaerobic conditions upon irradiation are potentially useful as radiosensitizing agents, but further research is needed to identify molecules that are incorporated by DNA polymerases and do not block further polymerization for this approach to be useful in cells.
authors.affiliation: Department of Chemistry Johns Hopkins University 3400 North Charles Street, Baltimore, Maryland 21218, United States.
authors.forename: Dianjie
authors.initials: D
authors.lastname: Hou
authors.forename: Marc M
authors.initials: MM
authors.lastname: Greenberg
mesh_terms: D001483:Base Sequence; D003432:Cross-Linking Reagents / Q000737:chemistry; D004247:DNA / Q000737:chemistry*; D004249:DNA Damage / Q000235:genetics / Q000528:radiation effects*; D004277:DNA, Single-Stranded; D004259:DNA-Directed DNA Polymerase / Q000737:chemistry*; D016166:Free Radical Scavengers / Q000737:chemistry*; D006846:Hydrocarbons, Halogenated / Q000737:chemistry*; D009690:Nucleic Acid Conformation; D009711:Nucleotides / Q000737:chemistry*; D009841:Oligonucleotides / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D010777:Photochemistry; D011827:Radiation; D011838:Radiation-Sensitizing Agents / Q000737:chemistry*; D060327:Solid-Phase Synthesis Techniques / Q000379:methods*; D014466:Ultraviolet Rays
chemical_list: D003432:Cross-Linking Reagents; D004277:DNA, Single-Stranded; D016166:Free Radical Scavengers; D006846:Hydrocarbons, Halogenated; D009711:Nucleotides; D009841:Oligonucleotides; D011838:Radiation-Sensitizing Agents; D004247:DNA; D004259:DNA-Directed DNA Polymerase; D010100:Oxygen