Figure 1. Activation of p53 and p21 in response to Aurora B inhibition. (A) U2OS cells were treated with 1 µM ZM447439 for 24 h. Nuclei were stained with Hoechst 33258. p21 was detected by immunostaining. Bar: 50 µm. (B) U2OS cells treated with 1 µM ZM447439 for 24 and 48 h were analyzed by FACS. (C) Cells were treated with 1µM ZM447439 and levels of p53 and p21 were determined by immunoblotting. β-actin served as a control for equal loading (D) U2OS cells were treated with 1 µM ZM447439 for 72 h. Four days later, senescent cells were detected by staining for β-galactosidase. (E) Cells stably expressing a control shRNA or a p53-specific shRNA were treated with ZM447439 for 36 h and p21 protein levels were determined by immunoblotting (F) U2OS cells were treated with AZD1152 as indicated and p21 levels were determined by immunoblotting. β-actin served as a control for equal loading. (G) U2OS cells were transfected with a control siRNA (ctrl) or with an Aurora B-specific siRNA. 48 h later, p21 levels were determined by immunoblotting. Tubulin served as control.