title: Antitumor bisdioxopiperazines inhibit yeast DNA topoisomerase II by trapping the enzyme in the form of a closed protein clamp.
abstract: The mechanism of inhibition of eukaryotic DNA topoisomerase II [DNA topoisomerase (ATP-hydrolyzing), EC 5.99.1.3] by a member of the bisdioxopiperazine family of anticancer drugs, ICRF-193, was investigated by using purified yeast DNA topoisomerase II. In the absence of ATP, ICRF-193 has little effect on the binding of the enzyme to various forms of DNA. In the presence of ATP, the drug converts the enzyme to a form incapable of binding circular DNA. Incubation of a preformed circular DNA-enzyme complex with ICRF-193 and ATP converts the complex to a form stable in molar concentrations of salt. These results can be interpreted in terms of the ATP-modulated protein-clamp model of type II DNA topoisomerases [Roca, J. & Wang, J. C. (1992) Cell 71, 833-840]; ICRF-193 can bind to the closed-clamp form of the enzyme and prevents its conversion to the open-clamp form. This interpretation is further supported by the finding that whereas both ATP and the drug are needed to form the salt-stable circular DNA-enzyme complex, ATP is not needed for maintaining this complex; furthermore, a signature of the closed-clamp form of the enzyme, Staphylococcus aureus strain V8 endoproteinase cleavage site at Glu-680, is observed if the enzyme is incubated with both ATP and ICRF-193. Inhibition of interconversion between the open- and closed-clamp forms of type II DNA topoisomerases offers a new mechanism in the selection and design of therapeutics targeting this class of enzymes.
authors.affiliation: Department of Biochemistry and Molecular Biology, Harvard University, Cambridge, MA 02138.
authors.forename: J
authors.initials: J
authors.lastname: Roca
authors.forename: R
authors.initials: R
authors.lastname: Ishida
authors.forename: J M
authors.initials: JM
authors.lastname: Berger
authors.forename: T
authors.initials: T
authors.lastname: Andoh
authors.forename: J C
authors.initials: JC
authors.lastname: Wang
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001665:Binding Sites; D004250:DNA Topoisomerases, Type II / Q000737:chemistry; D004270:DNA, Circular / Q000378:metabolism; D004271:DNA, Fungal / Q000378:metabolism; D054659:Diketopiperazines; D015394:Molecular Structure; D010879:Piperazines / Q000494:pharmacology*; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D012697:Serine Endopeptidases; D059005:Topoisomerase II Inhibitors
chemical_list: D000970:Antineoplastic Agents; D004270:DNA, Circular; D004271:DNA, Fungal; D054659:Diketopiperazines; D010879:Piperazines; D059005:Topoisomerase II Inhibitors; C070899:4,4'-(1,2-dimethyl-1,2-ethanediyl)bis-2,6-piperazinedione; C005147:5'-adenylyl (beta,gamma-methylene)diphosphonate; D000255:Adenosine Triphosphate; D012697:Serine Endopeptidases; C028344:glutamyl endopeptidase; D004250:DNA Topoisomerases, Type II; C002630:alpha,beta-methyleneadenosine 5'-triphosphate