FIG. 9.

Inhibition of CK1α expression by RNAi activates p53. (a, b, c) Cells were transfected with control or CK1α-specific siRNA (200 nM) for 48 h and treated with 10 Gy gamma irradiation (IR) for 6 h. MDM2 and p21 levels were determined by Western blotting. (d) U2OS cells stably transfected with p53-responsive BP100-luciferase reporter were treated as in panel c, and luciferase activity was determined using identical amount of cell lysate. Con Si, control siRNA; IR + CKI Si, gamma irradiation and CK1α-specific siRNA. (e, f) HCT116 cells were transfected with control siRNA (Con siRNA) or CK1α-specific siRNA (CK1 siRNA) (200 nM) for 24 h and treated with camptothecin (CPT) at the indicated concentrations for 24 h. Cell survival was determined by the MTT assay. OD450, optical density at 450 nm.