Centralspindlin component Cyk4 robustly localizes to the spindle midzone in cells treated with Cdk1 inhibitor RO-3306. (A and B) IF analysis of HeLa cells that were either control siRNA transfected and treated with RO-3306 (A) or transfected with siRNA-against Ect2 and treated with RO-3306 (B) for 5 min. Cells were fixed and costained using anti-NuMA (green) and anti-Cyk4 (red) antibodies. Yellow arrowheads depict NuMA localization at the equatorial membrane. The scale bar represents 10 µm. More than 30 cells were analyzed from three independent experiments, and the representative cells are shown here.