When the luciferase reporter assay was run in the EcR-GR cells to test activation of the SEPP1 promoter constructs, the GR exerted a repressive effect on this promoter (Figure 4). Even in the absence of dexamethasone activation, ponasterone A-induced activity was attenuated in the EcR-GR cells, as compared to 293-EcR cells with no active GR. When the EcR-GR cells were treated with dexamethasone, promoter activity was repressed by ~82% on the −1652 to +247 fragment, as compared to vehicle control (Figure 4A). Activation was repressed by ~37% on the −109 to +247 fragment under the same conditions (Figure 4B). Simultaneous treatment of the EcR-GR cells with ponasterone A and dexamethasone caused attenuation of ponasterone A activity, with an ~84% reduction in activation observed on the −1652 to +247 fragment as compared ponasterone A only treatment (0.6 vs. 3.9 fold change). An ~55% reduction was observed on the −109 to +247 fragment under the same conditions (2.9 vs. 6.5 fold change). In comparison, dexamethasone treatment was unable to exert a significant influence on ponasterone A activation in the 293-EcR cells, with
