INITIAL INTRACELLULAR EVENTS OF STEROID HORMONE ACTION

本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的事件 将军 这些研究特别具有现实意义，因为类固醇 激素受体可以说是最好理解的调节器， 真核基因转录 类固醇结合的第一步 胞内受体之后是受体类固醇的激活 DNA/核结合物种，然后与那些 参与转录调控的核受体位点 在特定细胞中选择基因。 我们把注意力集中在核问题上， 糖皮质激素受体的定位以及这些核受体 影响基因转录。 糖皮质激素受体主要是 在没有类固醇的情况下细胞质和几条证据 表明微管可能密切参与了 类固醇结合糖皮质激素受体的重新定位 细胞质到细胞核。 然而，这一假设现在已不可信 我们发现微摩尔浓度的微管破坏 秋水仙素对核转位无影响， 内源性诱导瞬时转染报告基因 受体。 核受体-类固醇复合物的机制 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 先前报道糖皮质激素诱导酪氨酸 转氨酶（达特）基因涉及一个新的顺式作用元件，称为 糖皮质激素调节元件（GME）。 我们现在发现， 88和67 kDa的显然是新的蛋白质以一种方式与该GME结合 与GME活性的表达相关。 另一个新的， 现在已经定义了达特基因的顺式作用元件，可以阻断 GME的影响。 这些新元素和结合蛋白提供了 修饰糖皮质激素调节基因的其它机制 表情 总的来说，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， 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.