title: Quinolone action against human topoisomerase IIalpha: stimulation of enzyme-mediated double-stranded DNA cleavage.
abstract: Several important antineoplastic drugs kill cells by increasing levels of topoisomerase II-mediated DNA breaks. These compounds act by two distinct mechanisms. Agents such as etoposide inhibit the ability of topoisomerase II to ligate enzyme-linked DNA breaks. Conversely, compounds such as quinolones have little effect on ligation and are believed to stimulate the forward rate of topoisomerase II-mediated DNA cleavage. The fact that there are two scissile bonds per double-stranded DNA break implies that there are two sites for drug action in every enzyme-DNA cleavage complex. However, since agents in the latter group are believed to act by locally perturbing DNA structure, it is possible that quinolone interactions at a single scissile bond are sufficient to distort both strands of the double helix and generate an enzyme-mediated double-stranded DNA break. Therefore, an oligonucleotide system was established to further define the actions of topoisomerase II-targeted drugs that stimulate the forward rate of DNA cleavage. Results indicate that the presence of the quinolone CP-115,953 at one scissile bond increased the extent of enzyme-mediated scission at the opposite scissile bond and was sufficient to stimulate the formation of a double-stranded DNA break by human topoisomerase IIalpha. These findings stand in marked contrast to those for etoposide, which must be present at both scissile bonds to stabilize a double-stranded DNA break [Bromberg, K. D., et al. (2003) J. Biol. Chem. 278, 7406-7412]. Moreover, they underscore important mechanistic differences between drugs that enhance DNA cleavage and those that inhibit ligation.
authors.affiliation: Department of Biochemistry, (Hematology/Oncology), Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA.
authors.forename: Kenneth D
authors.initials: KD
authors.lastname: Bromberg
authors.forename: Alex B
authors.initials: AB
authors.lastname: Burgin
authors.forename: Neil
authors.initials: N
authors.lastname: Osheroff
mesh_terms: D019943:Amino Acid Substitution; D000890:Anti-Infective Agents / Q000494:pharmacology*; D000951:Antigens, Neoplasm; D000970:Antineoplastic Agents / Q000494:pharmacology; D001483:Base Sequence; D001665:Binding Sites; D020134:Catalytic Domain / Q000235:genetics; D004247:DNA / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004249:DNA Damage; D004260:DNA Repair; D004250:DNA Topoisomerases, Type II / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins; D004789:Enzyme Activation / Q000187:drug effects; D005047:Etoposide / Q000494:pharmacology; D024841:Fluoroquinolones / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008954:Models, Biological; D009838:Oligodeoxyribonucleotides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D000890:Anti-Infective Agents; D000951:Antigens, Neoplasm; D000970:Antineoplastic Agents; D004268:DNA-Binding Proteins; D024841:Fluoroquinolones; D009838:Oligodeoxyribonucleotides; D011994:Recombinant Proteins; C070116:CP 115953; D005047:Etoposide; D004247:DNA; D004250:DNA Topoisomerases, Type II