雌激素受体（ER）与雌激素反应元件（ERE）结合以激活基因转录。最好的ERE位于近端基因启动子，但是最近的数据表明，只有少数ER结合位点位于近端启动子区域内。GREB1（乳腺癌1中雌激素调节的基因）是一种ER靶基因，可调节雌激素诱导的乳腺癌细胞增殖。我们确定了三个共识的ERE，位于最近的GREB1a转录起始位点上游的-21.2，-9.5和-1.6kb，似乎介导ER的远距离GREB1基因激活。所有三个ERE位点都使ER成核，类固醇受体辅激活因子-3（SRC-3），和RNA聚合酶II（PolII），并响应雌二醇进行组蛋白乙酰化。在所有三个ERE上雌激素刺激的ER结合是循环和同步的。雌激素激活了SRC-3和PolII对所有三个ERE的募集，但他莫昔芬未激活。相比之下,雌激素仅刺激PolII，而不刺激ER或SRC-3募集到GREB1核心启动子区域。远程组蛋白乙酰化，以三个ERE基序和GREB1核心启动子为中心，观察到对雌激素的反应，但对他莫昔芬没有反应。这些数据表明，雌激素刺激的GREB1转录可能涉及与所有三个远端共有ERE基序的协同ER结合。通过ER作用于多个ERE的远程激活可能比先前认识到的更常见。
The estrogen receptor (ER) binds to estrogen-responsive elements (EREs) to activate gene transcription. The best characterized EREs are located in proximal gene promoters, but recent data indicate that only a minority of ER binding sites lie within proximal promoter regions. GREB1 (gene regulated by estrogen in breast cancer 1) is an ER target gene that regulates estrogen-induced proliferation in breast cancer cells. We identified three
consensus EREs, located at -21.2, -9.5, and -1.6 kb upstream of the closest GREB1a transcription start site that appear to mediate long-range GREB1 gene activation by ER. All three ERE sites nucleate ER, steroid receptor coactivator-3 (SRC-3), and RNA polymerase II (Pol II) and undergo histone acetylation in response to estradiol. Estrogen-stimulated ER binding at all three EREs was cyclic and synchronous. SRC-3 and Pol II recruitment to all three EREs was activated by estrogen but not tamoxifen. In contrast, estrogen stimulated only Pol II and not ER or SRC-3 recruitment to the GREB1 core promoter regions. Long-range histone acetylation, centered on the three ERE motifs and the GREB1 core promoters, was observed in response to estrogen but not to tamoxifen. These data suggest that estrogen-stimulated GREB1 transcription may involve coordinated ER binding to all three distal
consensus ERE motifs. Long-range activation by ER acting at multiple EREs may be more common than previously appreciated.
