DNA cleavage induced by GE-2 is reversible and protein-linked. Assay mixtures contained DNA and 250 μM GE-2 in the absence of enzyme (-TII), DNA in the presence of topoisomerase IIα in the absence of GE-2 (+TII), or reaction mixtures that contained DNA, enzyme, and 250 μM GE-2 that were stopped with SDS (SDS). To determine whether the reaction was reversible, EDTA was added prior to SDS (EDTA). To determine whether the cleaved DNA was protein-linked, proteinase K treatment was omitted (ProK). The mobility of negatively supercoiled DNA (form I; FI), nicked circular plasmid (form II; FII), and linear molecules (form III; FIII) are indicated. Error bars represent the standard deviation of three independent experiments. A gel that is representative of three independent experiments is shown (top).