INITIAL INTRACELLULAR EVENTS OF STEROID HORMONE ACTION

这个项目的目标是定义初始的、细胞内的 糖皮质激素作用和类固醇激素作用事件 将军。这类研究具有特别的现实意义，因为类固醇 激素受体可以说是最被理解的调节器 真核基因转录。类固醇与细胞结合的第一步 细胞内受体之后是受体-类固醇的激活 一种DNA/核结合物种的复合体，然后与这些 参与转录调控的核受体位点 在特定细胞中选择的基因。我们把注意力集中在核问题上 糖皮质激素受体的定位及其核受体如何 影响基因转录。糖皮质激素受体主要是 在没有类固醇和几条证据的情况下细胞质 提示微管可能密切参与了 类固醇结合的糖皮质激素受体的重新定位 胞质进入细胞核。然而，这一假设现在已经不可信了。 我们发现随着微摩尔浓度的增加，微管破裂 秋水仙碱对核转位无影响 内源诱导人瞬时转基因报告基因的研究 感受器。核受体-类固醇复合体的作用机制 随着基因转录调控变得越来越复杂 发现新的DNA元件和反式作用因子。我们有过 先前报道糖皮质激素对酪氨酸的诱导作用 转氨酶(TAT)基因涉及一种新的顺式作用元件，称为 一种糖皮质激素调节元件(GME)。我们现在发现有两个 显然，88和67 kDa的新蛋白以一种方式与该GME结合 这与GME活性的表达有关。另一个新的， 现在已经定义了TAT基因的顺式作用元件，它可以阻止 GME的影响。这些新的元素和结合蛋白提供了 糖皮质激素调节基因修饰的其他机制 表情。总而言之，我们的发现有助于我们的长期目标 在分子水平上定义类固醇激素的作用，以及 了解它们在人体生理学中的作用。

The objective of this project is to define the initial, intracellular events of glucocorticoid hormone action and steroid hormone action in general. Such studies are of particular current relevance since steroid hormone receptors are arguably the best understood regulators of eukaryotic gene transcription. The first step of steroid binding to the intracellular receptor is followed by activation of the receptor-steroid complex to a DNA/nuclear-binding species that then associates with those nuclear acceptor sites involved in the regulation of transcription of selected genes in specific cells. We have concentrated on the nuclear localization of glucocorticoid receptors and how these nuclear receptors influence gene transcription. Glucocorticoid receptors are predominantly cytoplasmic in the absence of steroid and several lines of evidence suggest that microtubules may be intimately involved in the relocalization of steroid-bound glucocorticoid receptors from the cytoplasm to the nucleus. However, this hypothesis is now discredited by our finding that microtubule disruption with micromolar concentrations of colchicine had no effect on nuclear translocation as assayed by the induction of a transiently transfected reporter gene by endogenous receptors. The mechanism of how the nuclear receptor-steroid complexes regulate gene transcription is becoming increasingly complicated with the discovery of new DNA elements and trans-acting factors. We had previously reported that glucocorticoid induction of the tyrosine aminotransferase (TAT) gene involves a novel cis-acting element, called a glucocorticoid modulatory element (GME). We now find that two apparently novel proteins of 88 and 67 kDa bind to this GME in a manner that correlates with the expression of GME activity. Another new, cis-acting element of the TAT gene has now been defined that can block the effects of the GME. These new elements and binding proteins offer additional mechanisms for modifying glucocorticoid regulated gene expression. Collectively, our findings contribute to our long term goal of defining the action of steroid hormones at a molecular level and of understanding their role in human physiology.