Figure 1. CSN6 negatively regulates p57 stability. (A) HER2 and CSN6 negatively regulate the steady-state expression of p57. Equal amounts of cell lysates were immunoblotted with indicated antibodies. (B) CSN6 decreases the steady-state expression of p57 in a dose-dependent manner. 293T cells were co-transfected with indicated plasmids and increasing amounts of CSN6. Equal amounts of cell lysates were immunoblotted with indicated antibodies. (C) CSN6-mediated degradation of p57 is proteasome-dependent. 293T cells were co-transfected with the indicated plasmids. Cells were treated with MG132 for 6 h before harvesting. Equal amounts of cell lysates were immunoblotted with the indicated antibodies. (D) p57 turnover rate is decreased in CSN6-overexpressing cells. 293T cells transfected with the indicated plasmids were treated with cycloheximide (CHX) (100 µg/ml) for the indicated times. Cell lysates were immunoblotted with the indicated antibodies. Integrated OD values of p57 bands at each time point were measured using a densitometer. Levels of p57 at time zero were set at 100%. Remaining p57 is indicated graphically (right).