title: Stereochemistry-dependent bending in oligonucleotide duplexes induced by site-specific covalent benzo[a]pyrene diol epoxide-guanine lesions.
abstract: The apparent persistence length of enzymatically linearized pIBI30 plasmid DNA molecules approximately 2300 bp long, as measured by a hydrodynamic linear flow dichroism method, is markedly decreased after covalent binding of the highly tumorigenic benzo[a]pyrene metabolite 7R,8S-dihydroxy-9S,10R-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene [(+)-anti-BPDE]. In striking contrast, the binding of the non-tumorigenic, mirror-image 7S,8R,9R,10S enantiomer [(-)-anti-BPDE] to DNA has no measurable effect on its alignment in hydrodynamic flow gradients (< or = 2.2% of the DNA bases modified). In order to relate this effect to BPDE-nucleotide lesions of defined stereochemistry, the bending induced by site-specifically placed and stereochemically defined (+)- and (-)-anti-BPDE-N2-dG lesions in an 11mer deoxyoligonucleotide duplex was studied by ligation and gel electrophoresis methods. Out of the four stereochemically isomeric anti-BPDE-N2-deoxyguanosyl (dG) adducts with either (+)-trans, (-)-trans, (+)-cis, and (-)-cis adduct stereochemistry, only the (+)-trans adduct gives rise to prominent bends or flexible hinge joints in the modified oligonucleotide duplexes. Since both anti-BPDE enantiomers are known to bind preferentially to dG (> or = 85%), these observations can account for the differences in persistence lengths of DNA modified with either (+)-anti-BPDE or the chiral (-)-anti-BPDE isomer.
authors.affiliation: Chemistry Department, New York University, NY 10003, USA.
authors.forename: R
authors.initials: R
authors.lastname: Xu
authors.forename: B
authors.initials: B
authors.lastname: Mao
authors.forename: J
authors.initials: J
authors.lastname: Xu
authors.forename: B
authors.initials: B
authors.lastname: Li
authors.forename: S
authors.initials: S
authors.lastname: Birke
authors.forename: C E
authors.initials: CE
authors.lastname: Swenberg
authors.forename: N E
authors.initials: NE
authors.lastname: Geacintov
mesh_terms: D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000378:metabolism; D001483:Base Sequence; D004249:DNA Damage; D004591:Electrophoresis, Polyacrylamide Gel; D006147:Guanine / Q000737:chemistry* / Q000378:metabolism; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009841:Oligonucleotides / Q000737:chemistry*; D013057:Spectrum Analysis; D013237:Stereoisomerism
chemical_list: D009841:Oligonucleotides; D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide; D006147:Guanine; D000255:Adenosine Triphosphate