Unique and selective effects of five Ets family members, Elf3, Ets1, Ets2, PEA3, and PU.1, on the promoter of the type II transforming growth factor-beta receptor gene

Abstract

Previous studies have shown that the promoter of the type II TGF-beta receptor gene (TbetaR-II) is strongly stimulated by Elf3, a member of the Ets transcription factor family. The TbetaR-II gene behaves as a tumor suppressor and it is expressed in nearly all cell types, whereas Elf3 is expressed primarily in epithelial cells. Hence, the TbetaR-II gene is likely to be regulated by other Ets proteins in nonepithelial cells. In this study, we examined the effects of four other Ets family members (Ets1, Ets2, PEA3, and PU.1) on TbetaR-II promoter/reporter constructs that contain the two essential ets sites of this gene. These studies employed F9 embryonal carcinoma cells and their differentiated cells, because transcription of the TbetaR-II gene increases after F9 cells differentiate. Here we demonstrate that Ets2, which is expressed in F9-differentiated cells along with Elf3, does not stimulate or bind to the TbetaR-II promoter in these cells. In contrast, PEA3 stimulates the TbetaR-II promoter in F9-differentiated cells, but it inhibits this promoter in F9 cells. Thus, the effects of PEA3 on the TbetaR-II promoter are cell context-dependent. We also show that the effects of Elf3 are cell context-dependent. Elf3 strongly stimulates the TbetaR-II promoter in F9-differentiated cells, but not in F9 cells. In contrast to Elf3 and PEA3, Ets1 strongly stimulates this promoter in both F9 cells and F9-differentiated cells. Finally, we show that PU.1 exerts little or no effect on the activity of the TbetaR-II promoter. Together, our findings indicate that Elf3 is not the only Ets protein capable of stimulating the TbetaR-II promoter. Importantly, our findings also indicate that each of the five Ets proteins influences the TbetaR-II promoter in a unique manner because of important differences in their biochemical properties or their patterns of cellular expression.