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。类固醇与细胞内受体结合的第一步 之后是受体-类固醇复合体的激活 DNA/核结合物种，然后与这些核受体结合 参与特定基因转录调控的。它已经有很长时间了 被认为是整个细胞受体的半饱和 类固醇应该提供最大生物反应量的一半，并且 每种激动剂的各种诱导参数和部分 敌手应该是不变的。相比之下，我们对糖皮质激素的研究 酪氨酸氨基转移酶(TAT)的诱导显示 糖皮质激素激动剂的浓度需要达到一半最大 诱导(EC50)和部分药物产生的激动剂活性 抗糖皮质激素对所有反应基因的影响并不相同 同一间牢房。此外，TAT诱导的这两种属性在不同的时间内都不同 几个星期的时间。这种变化现在已经被复制了更少的 仅通过改变细胞密度就可以使其大于或等于40小时。我们不是 意识到之前任何关于细胞生长条件影响 部分抗类固醇的激动剂活性百分比或全抗类固醇的EC50 激动剂。这些变异被发现需要21个碱基对 TAT基因的序列。我们称之为21个碱基的序列，它作用于 与凝胶位移实验确定的反式作用因子相一致， 糖皮质激素调节元件(GME)。这个GME位于- 大鼠Tat基因的3654到-3634，是一个真实的转录元件 在某种程度上，它将其特性传递给异源基因和 推动者。一个包含这种新元素的模型被提出，它可以 第一次解释观察到的TAT诱导的变化。 未来对这一模型的研究应该会为 了解类固醇调节基因转录的调控和 基因转录的一般控制。

The objective of this project is to define the initial, intracellular events of glucocorticoid hormone action and steroid hormone action in general. 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 binds to those nuclear acceptor sites involved in the regulation of transcription of specific genes. It has long been thought both that half saturation of the whole cell receptors by steroid should afford half of the maximal amount of biological response and that the various induction parameters for each agonist and partial antagonist should be invariant. In contrast, our studies of glucocorticoid induction of tyrosine aminotransferase (TAT) revealed that the concentration of a glucocorticoid agonist required for half maximal induction (EC50) and the amount of agonist activity produced by a partial antiglucocorticoid were not the same for all responsive genes within the same cell. Furthermore, both properties for TAT induction varied over a period of several weeks. This variation has now been reproduced in less than or equal to 40 hr simply by changing the cell density. We are not aware of any previous report of cell growth conditions affecting either the percent agonist activity of a partial antisteroid or the EC50 of a full agonist. These variations were found to require the presence of a 21 bp sequence of the TAT gene. We call this 21 bp sequence, which acts in concert with a trans-acting factor identified by gel shift experiments, a glucocorticoid modulatory element (GME). This GME, which is located at - 3654 to -3634 of the rat TAT gene, is an authentic transcriptional element to the extent that it conveyed its properties to heterologous genes and promoters. A model incorporating this new element is advanced which can explain, for the first time, the observed variations of TAT induction. Future studies of this model should provide useful information for understanding the control of steroid-regulated gene transcription and the control of gene transcription in general.