Expression of SMRTβ promotes ligand-induced transactivation of wild-type nuclear receptors PML/RARα and RARα. Coexpression of SMRTβ with wild-type retinoid receptors (A) PML/RARα and (B) RARα in Jurkat cells, which do not endogenously express SMRTβ. Specific SMRT vectors were cotransfected with a DR5-tk-CAT reporter plasmid and expression plasmids for PML/RARα or RARα into Jurkat cells and tested for ligand response. Nuclear extracts of transfected Jurkat cells with PML/RARα or RARα were subjected to Western blot analysis. The arrow indicates expression of the 110-kDa PML/RARα (A) or the 50-kDa RARα (B). Assays were performed in triplicate and repeated at least 3 times. Bars represent standard deviation of the mean. Numbers in parentheses indicate the fold induction produced by ATRA. There was a significant difference between Jurkat cells transfected with SMRTβ compared with transfected PML/RARα (A) or RARα (B); ^*P < .05; ^**P < .01.