Figure 3.

RAR selective ligand enhances RARα ubiquitination. (A) An in vivo ubiquitin assay was used to assess the levels of RARα ubiquitin conjugation following 4 h of treatment with MG132 (MG, 5 µM) in the presence or the absence of TTNPB (1 µM). The blots were first probed with an ubiquitin specific antibody, and then stripped and re-probed for RARα as internal controls. (B) Quantification of the western blots as in (A) is presented as average fold variation of the ubiquitin signal normalized to the levels of immunopurified RARα following ligand induction and MG132 treatments in comparison to the MG132 only control. Error bars are the standard deviations of three independent experimental repeats (*p < 0.05). (C and D) The experimental procedures were as (A and B) except that the ubiquitination of RXRα protein was studied.