The As/IFN combination degrades Tax through the proteasome. (A) Effect of As/IFN or MG132 (5 μM) on the Tax protein level in HuT-102 cells after 48 hours of exposure to these drugs. Equal protein loading was assessed using anti-GAPDH antibodies. (B) Effect of As/IFN on Tax and RAR-α protein levels in HeLa cells cotransfected with PSG-Tax and PSG-RAR-α (underlined wells). Equal protein loading was assessed using anti-GAPDH antibodies. (C) Cycloheximide chase in HeLa cells cotransfected with PSG-Tax and PSG-RAR-α. Cells were exposed to As/IFN for 24 hours. When indicated, cycloheximide (50 μg/mL) or MG132 (50 μM) or both were added during the last 6 hours only.