Flötotto T, Niederacher D, Hohmann D, Heimerzheim T, Dall P, Djahansouzi S, Bender H G, Hanstein B
Universitäts-Frauenklinik, Heinrich Heine-Universität, Moorenstrasse 5, D-40225 Düsseldorf, Germany.
J Steroid Biochem Mol Biol. 2004 Feb;88(2):131-42. doi: 10.1016/j.jsbmb.2003.11.004.
The physiological effects of progesterone are mediated by the progesterone receptor (PR) isoforms PRA and PRB, transcribed from a single gene, under control of two distinct promoters. Both the isoforms display different, promoter- and cell line-specific transactivation properties. Upregulation of both isoforms in response to estradiol stimulation has been described, although the two promoters contain no classical estrogen response element (ERE). Therefore, we decided to investigate the regulation of PRB-expression through distinct estrogen receptor (ER)-isoforms: ERalpha and ERbeta We demonstrate, that in HeLa cells treated with E2, PRB promoter activity was enhanced (five-fold) by ERalpha, but not by ERbeta. ERbeta was also unable to stimulate activity of the PRB promoter in BT20 and Ishikawa cells, where ERalpha induced reporter activity by two-fold. Deletion of the AF1-but not AF2 domain from ERalpha resulted in loss of the transactivation potential in all cell lines tested. Furthermore, in BT20 cells deletion of the AF2 domain of ERalpha resulted in stronger transcriptional activation than that mediated through wild-type ERalpha. In SK-BR-3 cells both ERs repressed PRB promoter activity and this repression was enhanced by co-transfection of SRC1. However, strong estrogen-dependent stimulation was observed after deletion of AF2. We conclude that PRB expression is stimulated by ERalpha but not ERbeta in an unique, AF1-dependent but AF2-independent mechanism.
孕酮的生理作用由孕酮受体（PR）亚型PRA和PRB介导，这两种亚型由单个基因转录而来，受两个不同启动子的控制。这两种亚型表现出不同的、启动子和细胞系特异性的反式激活特性。尽管两个启动子中都没有经典的雌激素反应元件（ERE），但已有文献报道，在雌二醇刺激下，这两种亚型均会上调。因此，我们决定研究通过不同的雌激素受体（ER）亚型：ERα和ERβ对PRB表达的调控。我们证明，在用E2处理的HeLa细胞中，PRB启动子活性被ERα增强（五倍），而不是被ERβ增强。在BT20和Ishikawa细胞中，ERβ也无法刺激PRB启动子的活性，而在这些细胞中ERα可使报告基因活性增加两倍。从ERα中缺失AF1结构域而非AF2结构域会导致在所有测试细胞系中反式激活潜能丧失。此外，在BT20细胞中，缺失ERα的AF2结构域会导致比野生型ERα介导的更强的转录激活。在SK-BR-3细胞中，两种ER均抑制PRB启动子活性，并且通过共转染SRC1可增强这种抑制作用。然而，在缺失AF2后观察到强烈的雌激素依赖性刺激。我们得出结论，PRB表达通过一种独特的、依赖AF1但不依赖AF2的机制被ERα而非ERβ刺激。
