Fig. (5). Protein stability of GSK 3β wt and its SUMO mutant Ha –GSK 3β or GSK 3β SUMO mutant (K292R) was transfected into COS-1 cells and the cells treated with cyclohexamide. The GSK 3β proteins were chased for the indicated time periods. Ha–GSK 3β proteins were immunoprecipitated with a polyclonal anti- Ha antibody and subjected to SDS-PAGE followed by western blotting with a monoclonal GSK 3β antibody (A). To monitor the protein amount, an equal amount of cell lysate was subjected to western blotting with an actin antibody. Results shown are one of five repeated experiments. Quantifi-cation of the pulse-chase experiment is shown in (B) by image analysis with the Fuji Image Quant software.