Size exclusion HPLC analysis of [³H]-t-RA binding to nuclear (A) and cytosolic (B) extracts prepared from pMT2/PLZF/RARα transiently transfected COS-1 cells. (•) [³H]-t-RA alone; (○) [³H]-t-RA plus 200-fold mol/L excess of unlabeled t-RA. The Superose 6 HR 10/30 size exclusion column was calibrated with the indicated marker proteins (in thousands) as described in Materials and Methods.