FIGURE 3.

SUMOylation of VCP is a stress response. A, oxidative and ER stress increase global SUMOylation. HEK293 cells were treated with stress inducers and harvested at various time points as indicated. The global SUMO levels were determined by immunoblotting for SUMO-1. The concentration of each stressor is: paraquat (250 μm), sodium arsenite (100 μm), MG132 (15 μm), and tunicamycin (5 μg/ml). B, the SUMOylation of VCP is enhanced by arsenite or MG132 in a dose-dependent manner. HEK293 cells were treated with MG132 for 4 h or arsenite for 2 h at increasing concentrations, and the SUMOylation of endogenous VCP was determined using immunoprecipitation (IP)-immunoblotting as described in the legend to Fig. 1D. C, SUMOylation of VCP increases in vivo during stress. Wild type C57/B6 mice were treated with sodium arsenite or paraquat via intraperitoneal injection for indicated time. SUMOylation of VCP in the liver was analyzed by immunoprecipitation and immunoblotting.