Figure 4.

PML reverses Tax repression. (A) PML blocks GR repression. CV1 cells were transfected as in Fig. 2A. CMX PML was used at 180 ng as the Tax expression vector. (B) Experiment was done as in A, but pcTax was used at 90 ng and CMX PML was transfected at the indicated molar ratio. After transfection cells are grown for 12 hr in the presence of 100 nM of dexamethasone before harvesting. (C) Tax represses Gal-4 RXRαF and PML restores activity. Cells were transfected as before. Gal-4 RXRαF was transfected at 120 ng and CMX PML and Tax expression vectors at 90 and 180 ng, respectively. Transfected cells were treated with 9-cis RA at 1 μM for 8 hr before the assay. In the histogram two bars of activity are used (100 and 1,200 arbitrary units), as the activity of the reporter is dramatically stimulated in the presence of PML protein.