(B) Purified FLAG-CK1α was incubated with ATP, GST-MDMX, GST-β-catenin-1-200, pDI peptide (LTFEHYWAQLTS, 5 µM), and pDI3A peptide (LTAEHYAAQATS, 5 µM). β-catenin pS45 level was determined by western blot. 