title: The human DNA repair factor XPC-HR23B distinguishes stereoisomeric benzo[a]pyrenyl-DNA lesions.
abstract: Benzo[a]pyrene (B[a]P), a known environmental pollutant and tobacco smoke carcinogen, is metabolically activated to highly tumorigenic B[a]P diol epoxide derivatives that predominantly form N(2)-guanine adducts in cellular DNA. Although nucleotide excision repair (NER) is an important cellular defense mechanism, the molecular basis of recognition of these bulky lesions is poorly understood. In order to investigate the effects of DNA adduct structure on NER, three stereoisomeric and conformationally different B[a]P-N(2)-dG lesions were site specifically incorporated into identical 135-mer duplexes and their response to purified NER factors was investigated. Using a permanganate footprinting assay, the NER lesion recognition factor XPC/HR23B exhibits, in each case, remarkably different patterns of helix opening that is also markedly distinct in the case of an intra-strand crosslinked cisplatin adduct. The different extents of helix distortions, as well as differences in the overall binding of XPC/HR23B to double-stranded DNA containing either of the three stereoisomeric B[a]P-N(2)-dG lesions, are correlated with dual incisions catalyzed by a reconstituted incision system of six purified NER factors, and by the full NER apparatus in cell-free nuclear extracts.
authors.affiliation: Chemistry Department, Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM/ULP, Strasbourg, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Mocquet
authors.forename: Konstantin
authors.initials: K
authors.lastname: Kropachev
authors.forename: Marina
authors.initials: M
authors.lastname: Kolbanovskiy
authors.forename: Alexander
authors.initials: A
authors.lastname: Kolbanovskiy
authors.forename: Angels
authors.initials: A
authors.lastname: Tapias
authors.forename: Yuqin
authors.initials: Y
authors.lastname: Cai
authors.forename: Suse
authors.initials: S
authors.lastname: Broyde
authors.forename: Nicholas E
authors.initials: NE
authors.lastname: Geacintov
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Egly
mesh_terms: D001483:Base Sequence; D001564:Benzo(a)pyrene / Q000737:chemistry*; D018736:DNA Adducts / Q000737:chemistry*; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000737:chemistry*; D006801:Humans; D008958:Models, Molecular; D008968:Molecular Conformation; D013237:Stereoisomerism
chemical_list: D018736:DNA Adducts; D004268:DNA-Binding Proteins; C056612:benzo(a)pyrene-DNA adduct; C086984:XPC protein, human; D001564:Benzo(a)pyrene