TRα homodimers (left panels), RARα homodimers (right panels), and RARα/TRα heterodimers (center panels) were assembled on the indicated DNA probes in the presence of the GST-SMRT construct as in Fig. 6. T3 alone, ATRA alone, or T3 and ATRA together were added at 1 µM concentrations, and the resulting protein/DNA complexes were resolved by EMSA. The amount of receptor/DNA complex bound by SMRT (i.e. supershifted by GST-SMRT) was quantified for each condition and is presented (cross-hatched bars). TRα, RARα, and GST-SMRT were used at 40, 28, and 200 ng per assay, respectively. The mean and se of three experiments are shown.