Figure 4.
ICE assay of topoisomerase II covalent complexes. HeLa cells were treated with various etoposide concentrations for 1 hr. The ICE assay was performed as described in Basic Protocol 3, and the slot blots of DNA recovered from the pellet after CsCl centrifugation, probed with an antibody directed against topoisomerase IIα, are shown in panel (A). The signal arises from topoisomerase II that covalently associates with DNA. Panel (B) shows a quantification of the signal from the blot shown in panel A.