Antitumor bisdioxopiperazines inhibit yeast DNA topoisomerase II by trapping the enzyme in the form of a closed protein clamp

Joaquim Roca, Ryoji Ishida, James M. Berger, Toshiwo Andoh, James C. Wang

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The mechanism of inhibition of eukaryotic DNA topoisomerase II [DNA topoisomerase (ATP-hydrolyzing), EC] 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. and 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.

Original languageEnglish (US)
Pages (from-to)1781-1785
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number5
StatePublished - Mar 1 1994
Externally publishedYes


  • bis(2,6-dioxopiperazines)
  • drug design
  • enzyme mechanism

ASJC Scopus subject areas

  • General


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