[Inhibition by ellipticine derivatives of the reactions catalysed by the topoisomerases: preferential inhibition of topoisomerase II].

We have studied inhibitory effects of ellipticine derivatives on the topoisomerisation reactions by Rat liver enzymes. We used the reactions of relaxation of supercoiled DNA, catalysed by topoisomerase I without ATP and by topoisomerase II with ATP, and also the reaction of decatenation of DNA networks by topoisomerase II. When studying intercalating agents--as elliptieine derivatives are--a problem arose. To distinguish relaxed DNA from native DNA we run our samples in electrophoretic gels containing an intercalating agent: chloroquine. Topoisomerase II, which was inhibited at concentrations about 10(-6) M, was more sensitive than topoisomerase I.