Saturation binding (A) and Scatchard plot analyses (B) for the binding of [³H]-t-RA to bcr3-PML/RARα. Nuclear extracts from pSG5/bcr3-PML/RARα transiently transfected COS-1 cells were incubated with the indicated concentrations of [³H]-t-RA and analysed using PD10 desalting columns as described in Materials and Methods. Nonspecific binding activity (○) was subtracted from total binding activity (•) to calculate specific binding activity (▪). Specific t-RA binding activity (▪) was also plotted in the form of a Scatchard plot (B).