In addition to the region we primarily focused on, the −109 to +247 fragment, it appears there are other dexamethasone-dependent repressive elements acting within the −1652 to +247 fragment. Ponasterone A-induced activation is reduced on this fragment as compared to the −109 to +247 fragment (Figures 2, 4 and 5). Plus, attenuation of the SEPP1 promoter was observed on the larger fragment in the EcR-GR cells following dexamethasone treatment, but was not observed on the smaller fragment (Figure 4). In silico evaluation of this region identified additional potential GREs, but again, these sites are primarily half-sites and do not appear to be classical GREs. Furthermore, the region 5′ to −109 in the SEPP1 promoter appears to have additional repressive elements (Figure 2). These elements are not well characterized and in silico evaluation did not reveal obvious potential repressive elements; however, one complex repeat region has demonstrated repression of SEPP1 expression with certain polymorphisms (Al-Taie et al. 2002). This region overlaps the 5′ end of the promoter reporter construct −391 to +247 we used in this study, and perhaps was responsible for the attenuated response we observed compared to the −109 to +247 promoter construct.
