Genistein is an isoflavone and an inhibitor of tyrosine protein kinases.  It has been reported to induce topo II dependent cleavages (Biochem. Pharmacol. 39:737-740 [1990]).  TopoGEN provides this reagent as a control poison/inhibitor of topoisomerase II (Note, Genistein may also inhibit topoisomerase I.)  For in vitro cleavage detection, we recom- mend that the drug be tested over a wide range of uM concentrations; however, cleavages are strongly influenced by the amount of topoisomerase in the reaction as well as the type of assay being employed (SDSK+ vs. Radioactive End Labeled DNA vs. testing for plasmid cleavages).  Note that large amounts of enzyme will be required to detect cleavage complex, compared to assays that measure catalytic activity.