Androgen induction of cyclin-dependent kinase inhibitor p21 gene: role of androgen receptor and transcription factor Sp1 complex.
Androgen induction of cyclin-dependent kinase inhibitor p21 gene: role of androgen receptor and transcription factor Sp1 complex.
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DOI：
10.1210/mend.14.5.0461
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发表时间：
2000-05
影响因子：
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通讯作者：
S. Lu;Guido Jenster;Daniel E. Epner
中科院分区：
文献类型：
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作者：
S. Lu;Guido Jenster;Daniel E. Epner
先前的研究表明，雄激素上调p21(WAF1，CIP1，SDI1，CAP20)基因的表达，该基因在其近端的启动子区域含有一个典型的雄激素反应元件(ARE)。我们进行了目前的研究，以确定p21启动子中除Are以外的元件是否介导了雄激素的作用。我们发现ARE的缺失并没有完全消除启动子对雄激素的反应性，这表明p21核心启动子中的额外顺式调节元件也可能参与雄激素的反应性。P21核心启动子富含GC，含有转录因子Sp1的6个结合位点。我们确定了这些Sp1中的一个或多个是否介导了p21启动子的雄激素反应。为此，我们使用了p21启动子-荧光素酶报告构建的瞬时转染实验。缺少ARE但包含所有六个Sp1位点的构建体的报告活性被雄激素诱导了大约3倍。Sp1-3突变几乎消除了基础启动子活性和雄激素反应性，而Sp1-1和Sp1-2位点缺失以及Sp1-4、Sp1-5和Sp1-6位点突变影响相对较小。我们还使用哺乳动物单杂交实验和免疫共沉淀实验证明雄激素受体(AR)和转录因子Sp1相互作用。目前的研究提出了一种模型，在该模型中，AR和转录因子Sp1不仅结合到各自的p21启动子内的共同位点，而且相互复合，从而招募辅助激活因子和通用转录因子，并诱导p21转录。
Previous studies have shown that androgen up-regulates expression of the p21 (WAF1, CIP1, SDI1, CAP20) gene, which contains a canonical androgen response element (ARE) in its proximal promoter region. We undertook the current studies to determine whether elements in the p21 promoter other than the ARE mediate androgen action. We found that deletion of the ARE did not completely abolish the promoter responsiveness to androgen, suggesting that additional cis-regulatory elements within the p21 core promoter may also be involved in androgen responsiveness. The p21 core promoter is GC-rich and contains six binding sites for transcription factor Sp1. We determined whether one or more of these Sp1 sites mediate androgen responsiveness of the p21 promoter. To do so, we used a transient transfection assay with p21 promoter-luciferase reporter constructs. The reporter activity of a construct lacking the ARE but containing all six Sp1 sites was induced approximately 3-fold by androgen. Mutation of Sp1-3 nearly eliminated basal promoter activity as well as androgen responsiveness, whereas deletion of Sp1-1 and Sp1-2 sites and mutation of Sp1-4, Sp1-5, and Sp1-6 sites had relatively little effect. We also used the mammalian one-hybrid assay and coimmunoprecipitation assay to show that androgen receptor (AR) and transcription factor Sp1 interact with one another. The current studies suggest a model in which AR and transcription factor Sp1 not only bind to their respective consensus sites within the p21 promoter, but also complex with one another, thereby recruiting coactivators and general transcription factors and inducing p21 transcription.