Figure 4.

SUMOylation sustains the stability of NPM-ALK protein. Jurkat cells were transfected with wild-type NPM-ALK, NPM-ALK^K24R, NPM-ALK^K32R, or NPM-ALK^K24,32R construct for 0, 24 or 48 hours and then treated with the protein synthesis inhibitor CHX for an additional 48 hours. There was minimal decrease in the levels of NPM-ALK mutants at 24 hours (data not shown). Nonetheless, the decrease in the expressions of NPM-ALK^K32R was more pronounced than the decrease in NPM-ALK^K24R expression at 48 hours. Importantly, this decrease was much more pronounced when the NPM-ALK^K24,32R double mutant was used. In contrast, wild-type NPM-ALK protein expression did not show any evidence of decreased expression even at 48 hours after treatment with CHX. β-Actin shows equal loading of the proteins.