C HEK293T cells were transfected with the FLAG-GPX1, HA-CUEDC2, and Myc-ubiquitin plasmids as indicated and treated with MG-132 (10 µM) for 6 hours before harvest. Cell lysates were immunoprecipitated (IP) with anti-FLAG (M2). The immunoprecipitates were analyzed by western blot using an anti-GPX1 antibody. Whole-cell lysates (WCL) were analyzed by Western blots with anti-FLAG or anti-HA antibody to determine the protein of Flag-GPX1 and HA-CUEDC2. 