Fig. 4.

TNFα- and 9cRA-induced SUMO(1)ylation of RXRα involves activation of JNK. (A) HuH-7 cells were transfected with F-RXRα and SUMO1, pretreated with either vehicle (Veh) or 30 μM SP600125 for 30 minutes prior to vehicle or 10 ng/ml TNFα for 30 minutes; harvested; and immunoblotted with either antibodies specific for FLAG, p-cjun (phospho-c-jun), or β-actin. (B) Huh-7 cells were transfected as in A and treated with vehicle or 1 μM 9cRA for 30 minutes prior to harvest and immunoblotting. (C) HuH-7 cells were transfected with F-RXRα and SUMO1 pretreated with either vehicle or 20 μM PD98059 for 30 minutes prior to vehicle or 10 ng/ml TNFα for 30 minutes, harvested, and immunoblotted with either FLAG, p-ERK, or β-actin. Note: all images are representative blots from a minimum of three experiments. Arrow denotes F-RXRα, and arrowhead denotes Su-F-RXRα. (D) Densitometric analysis of blots in A–C in which the SUMO–F-RXRα band intensity is plotted relative to the F-RXRα band. Vehicle-treated samples (i.e., absence of TNFα or 9cRA) are normalized to 1.0, data are presented as mean + S.E. and *P < 0.05, relative to the vehicle-treated control.