4.5. Topoisomerase II Cleavage Complex Assay

Cleavage complex assay was performed as described previously and reported [32]. Briefly, pBR322 (Thermo Scientific, Waltham, MA, USA) was incubated with topoisomerase IIα enzyme (Inspiralis Ltd.) and the reaction was stopped by adding stop buffer. The samples were digested with proteinase K (1.38 mg/mL, #P4850, Sigma, St. Louis, MO, USA) at 45 °C for 30 min. The samples were electrophoresed on an EtBr-containing agarose gel (1.5% agarose in 1X TAE buffer, 0.5 μg/mL EtBr). The linear DNA bands were visualized following the same method described as for the DNA topoisomerase II relaxation assay.