FIG. 11.

Topoisomerase IIα is required for PKCδ-induced apoptotic cell death in response to genotoxic stress. (A) MOLT-4 cells were treated with ara-C for the indicated times in the presence (open bar) or absence (closed bar) of ICRF-193. The percentages of apoptotic cells were determined by TUNEL assays. The results are represented as means ± standard deviations (error bars) obtained from four fields of 100 to 300 cells (each field) and three independent experiments. (B) U2-OS cells were transfected with the indicated siRNAs for 48 h and then left untreated (−) or treated (+) with ara-C for 4 h. Cell lysates were subjected to immunoblot (IB) analysis with anti-topoisomerase IIα (anti-TopoIIα) or antitubulin. Nuclear lysates were analyzed by decatenation assays (bottom blot). The cells had been transfected with scrambled siRNA (lanes S), topoisomerase IIα siRNA1 (lanes 1), or topoisomerase IIα siRNA2 (lanes 2). Nuc. Lysates, nuclear lysates; Cat. KDNA, catenated KDNA; Decat. KDNA, decatenated KDNA. (C) U2-OS cells transfected with the indicated siRNAs were left untreated (−) or treated (+) with rottlerin for 1 h followed by treatment with ara-C (+) for 24 h. The percentages of apoptotic cells were determined by TUNEL assays. The results are represented as means ± standard deviations (error bars) obtained from four fields of 100 to 300 cells, each performed over three independent experiments. Cell lysates were also analyzed by immunoblotting (IB) with anti-topoisomerase IIα (anti-TopoIIα) or antitubulin.