The 5'-untranslated region (5'-UTR) (-575) of p27 gene is unlikely to contain cryptic transcription factor binding sites. (a) Schematic drawing (adapted from the references [11, 34]) of the pGL3-control-p27-5'-UTR-luciferase reporter plasmid. (b) The ER-negative MDA-MB 231 cells were transfected with -575 p27 (p27-5'-UTR) -luciferase reporter plasmid and then treated with either vehicle or actinomycin D(0.5 μg/ml) . One hour after the addition of either vehicle or actinomycin D, the cells were exposed to vehicle, tamoxifen (1 μM) or 4-hydroxytamoxifen (1 μM) for another 24 hours. (c) Same as in Figure 4b above, except that the cells were exposed to vehicle, all-trans-retinoic acid (atRA) (1 μM) or 9-cis-retinoic acid (9cRA) (1 μM) for 24 hours. (d) Same as in Figure 4b above, except that the cells were exposed to vehicle, 4-methyl-UAB30 (4meUAB30) (1 μM) or UAB30 (1 μM) for 24 hours. (e) Same as in Figure 4b, except that the cells were exposed to vehicle or dexamethasone (1 μM). All assays were performed in triplicates and the transfection experiments were repeated three times.