In order to evaluate the interplay between the VgEcR-RXR system and the GR on the SEPP1 promoter, the 293-EcR cell line was engineered to express a DsRed2-labeled, functional human GR. The pLTRluc reporter assay confirmed that the GR is activated by dexamethasone in these EcR-GR cells, with minimal activity in HEK-293 or 293-EcR cells (Figure 3). To evaluate possible cross-talk between VgEcR-RXR and GR, ponasterone A was used to treat 293-EcR or EcR-GR cells, transiently transfected with pLTRluc, and only background reporter activity was seen (data not shown).
