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. Author manuscript; available in PMC: 2009 Nov 11.
Published in final edited form as: Biochemistry. 2008 Oct 16;47(45):11900–11908. doi: 10.1021/bi800981j

FIGURE 6.

FIGURE 6

Role of the 26S proteasome in the degradation of topoisomerase IIα– and β–DNA cleavage complexes induced by genistein and etoposide. The ICE bioassay was utilized to monitor levels of isoform-specific DNA cleavage complexes. CEM cells were treated in the absence of compound or in the presence of 2 μM MG132 (a proteasome inhibitor), 50 μM genistein, or 50 μM etoposide for 1 h. In some cases, cells were transferred to drug-free medium for a 30 min recovery period following treatment. When experiments were carried out in presence of MG132 (2 μM), the proteasome inhibitor was included in cell cultures for 30 min prior to the addition of genistein or etoposide and also was present during the recovery period. Data for cleavage complexes mediated by topoisomerase IIα (hTIIα; open bars) or β (hTIIβ; closed bars) are shown. Levels of cleavage complexes prior to recovery were set to 100%. Error bars represent the standard deviation for three independent experiments.