The ChT domain of Topo IIα is necessary for chromosome condensation and segregation in mitosis. (A and B) Still images taken from digital time-lapse imaging of live cells after depletion of endogenous Topo IIα and induced with doxycycline to express mCherry–Topo IIα or mCherry–Topo IIα ΔChT. Cells were assayed after a double thymidine synchrony and release protocol in conjunction with shRNA-mediated depletion of the endogenous Topo IIα and DNA observed via imaging of Hoechst. Red boxed regions are enlarged in B to highlight the differences in metaphase chromatin morphology. Frames were taken at 5-min intervals. Time is indicated (hours:minutes) in each movie frame. Bars, 10 µm. (C) Distribution of phenotypes seen in live single cells described in A and B. Induction of mCherry–Topo IIα rescues chromosome condensation and segregation defects, whereas Topo IIα ΔChT fails to rescue. WT − Dox, n = 96; WT + Dox, n = 100; ΔChT − Dox, n = 61; ΔChT + Dox, n = 82.