Ligand-dependent transcriptional activity of wild-type or mutant PML/RARα chimeric protein on βRARE. Luciferase activity of samples was normalized to β-galactosidase activity and then calculated as fold increases of luciferase activity to that of samples in the absence of ATRA. Each point represents the mean of triplicated results, and bars denote SD. *Significant difference as compared with the luciferase activities of wild-type PML/RARα in the presence of the corresponding concentrations of ATRA.