Cks promotes APC/C–dependent destruction of cyclin B1 and securin. (A and B) Cells were treated with siRNA pools targeting Cks1 (siCks1; control) or both Cks1 and Cks2 (siCks1 and 2). Total amounts of siRNA were kept equal. Cells transfected with either securin-Venus (A) or cyclin B1–Venus (B) and expressing similar fluorescent protein levels were followed during mitosis (see Fig. S2 A for quantified fluorescence levels and total destruction times). (C) Fluorescence levels plotted over time starting 3 min before NEB are shown. Data are representative of three independent experiments for each condition. Numbers indicate minutes. Bars, 10 µM.