title: Position-specific trapping of topoisomerase II by benzo[a]pyrene diol epoxide adducts: implications for interactions with intercalating anticancer agents.
abstract: DNA topoisomerase II (Top2) is the target of some of the most effective anticancer DNA intercalators. To determine the effect of intercalating ligands at defined positions relative to a known DNA cleavage site for human Top2alpha, we synthesized oligodeoxynucleotides containing single trans-opened benzo[a]pyrene 7,8-diol 9,10-epoxide (DE) deoxyadenosine (dA) adducts of known absolute configuration, placed at specific positions in a duplex sequence containing staggered Top2 cleavage sites on both strands. Because the orientations of the intercalated hydrocarbon are known from NMR solution structures of duplex oligonucleotides containing these dA adducts, a detailed analysis of the relationship between the position of intercalation and trapping of Top2 is possible. Our findings demonstrate that (i) Top2 cleavage complexes are trapped by intercalation of the hydrocarbon at either of the staggered cleavage sites or immediately adjacent to the base pairs flanking the cleavage sites within the stagger; (ii) both concerted and nonconcerted cleavage by both subunits of a Top2 homodimer were detected depending on the position of the benzo[a]pyrene DE dA adduct; and (iii) intercalation immediately outside of the staggered Top2 cleavage site, and to a lesser extent in the middle of the stagger, prevents Top2 from cleaving DNA at this site, consistent with the effect of some intercalators as suppressors of Top2-mediated DNA cleavage. These results identify specific binding sites for intercalators that result in trapping of Top2. Such poisoning of Top2 by bulky polycyclic aromatic hydrocarbon DE adducts constitutes a potential mechanism for their carcinogenic activity.
authors.affiliation: Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, National Institutes of Health/DHHS, Building 37, Bethesda, MD 20892, USA.
authors.forename: Qasim A
authors.initials: QA
authors.lastname: Khan
authors.forename: Glenda
authors.initials: G
authors.lastname: Kohlhagen
authors.forename: Richard
authors.initials: R
authors.lastname: Marshall
authors.forename: Caroline A
authors.initials: CA
authors.lastname: Austin
authors.forename: Govind P
authors.initials: GP
authors.lastname: Kalena
authors.forename: Heiko
authors.initials: H
authors.lastname: Kroth
authors.forename: Jane M
authors.initials: JM
authors.lastname: Sayer
authors.forename: Donald M
authors.initials: DM
authors.lastname: Jerina
authors.forename: Yves
authors.initials: Y
authors.lastname: Pommier
mesh_terms: D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D000951:Antigens, Neoplasm; D000970:Antineoplastic Agents / Q000494:pharmacology; D001483:Base Sequence; D001665:Binding Sites; D018736:DNA Adducts / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D004250:DNA Topoisomerases, Type II / Q000737:chemistry* / Q000187:drug effects* / Q000378:metabolism; D004268:DNA-Binding Proteins; D006801:Humans; D066298:In Vitro Techniques; D007364:Intercalating Agents / Q000494:pharmacology; D008958:Models, Molecular; D015394:Molecular Structure; D000075223:Poly-ADP-Ribose Binding Proteins; D011994:Recombinant Proteins / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D000951:Antigens, Neoplasm; D000970:Antineoplastic Agents; D018736:DNA Adducts; D004268:DNA-Binding Proteins; D007364:Intercalating Agents; D000075223:Poly-ADP-Ribose Binding Proteins; D011994:Recombinant Proteins; D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide; D004250:DNA Topoisomerases, Type II; C000618811:TOP2A protein, human