MOLECULAR MECHANISMS OF GLUCOCORTICOID HORMONE ACTION

了解基因表达的调控机制是 对理解发展和分化至关重要，因此， 癌症和其他疾病，可能会出现当这些过程出错。 详细了解类固醇激素依赖性调节 机制可能导致现有治疗方案的改进， 开发新的干预途径，特别是 内分泌依赖性肿瘤 我们的长期目标是了解这些 类固醇控制靶基因表达的机制。 过去的研究工作集中在类固醇的相互作用 DNA受体 在这一框架内，新的战略和 申请将涉及三个具体问题。 I. 糖皮质激素和孕激素受体如何区别 诱导靶基因？ DNA结合之间存在一些差异， 糖皮质激素、孕酮、盐皮质激素和雄激素域 受体。 我们的研究表明糖皮质激素和孕酮 受体识别靶DNA序列相似，如果不是相同的。 这就提出了一个问题，即对这两种激素的反应是否 受受体表达部位的严格控制，或者 微妙因素也起着重要作用。 建议的实验 本节将详细讨论生物学上的基本难题， 以上 二. 体内靶元件的受体占有情况如何 与激素反应性有关吗我们提出了一种新的逆转录病毒 载体方法来评估受体占有的相对程度， 其靶位点在体内作为生物活性的函数， 激素反应元件 激素反应的幅度将是 通过修饰启动子来改变。上下文，目标的序列 位点，或通过刺激其他细胞信号转导途径。 在刺激神经细胞中的类固醇依赖性改变的另外方面， 其他细胞信号转导途径。 类固醇的其他方面- 染色质结构和转录起始的依赖性改变 还将评估复杂负载。 三. 糖皮质激素受体是如何找到靶元件的？ 基因组？ 在哺乳动物基因组中， 基因. 受体通过以下方式搜索靶位点的模型： 扩散或通过沿着滑动DNA不能令人满意地解释 细胞核中DNA的数量和密度所带来的困难 环境 我们提出糖皮质激素受体可以搜索DNA 通过域间转移。 类似于泰山摇摆葡萄藤，这 这种机制设想受体在DNA位点之间转移， 与DNA分离 分子、动力学和物理的结合 将采用各种方法来测试这一提议。

Understanding the mechanisms of regulation of gene expression is essential to comprehension of development and differentiation, and thus, cancer and other disorders that may arise when these processes go awry. A detailed understanding of steroid hormone-dependent regulatory mechanisms may lead to improvement of existing therapeutic regimens and the development of novel avenues for intervention, particularly in endocrine-dependent neoplasia. Our long term goal is to understand these mechanisms through which steroids control expression of target genes. Past research efforts have focused on the interaction of steroid receptors with DNA. Within this framework, new strategies and applications will address three specific questions. I. How do glucocorticoid and progesterone receptors differentially induce target genes? There are a few differences among the DNA binding domains of glucocorticoid, progesterone, mineralocorticoid, and androgen receptors. Our studies imply that glucocorticoid and progesterone receptors recognize target DNA sequence similarly, if not identically. This raises the question of whether response to these two hormones is controlled strictly by the site of receptor expression or whether more subtle factor also significantly contribute. Experiments proposed in this section address in detail the fundamental biological conundrum posed above. II. How well does receptor occupancy of target elements in vivo correlate with hormone responsiveness? We propose a novel, retroviral vector approach to assess the relative extent of receptor occupancy of its target site in vivo as a function of the biological activity of the hormone response element. The magnitude of hormone response will be altered by modifying the promoter. context, the sequence of the target site, or by stimulation of other cell signal transduction pathways. Additional aspects of steroid-dependent alterations in stimulation of other cell signal transduction pathways. Additional aspects of steroid- dependent alterations in chromatin structure and transcription initiation complex loading will also be assessed. III. How does the glucocorticoid receptor find target elements in the genome? Buried within the mammalian genome are a handful of target genes. Models in which receptor conducts a search for targets sites by diffusion or by sliding along the DNA do not satisfactorily account for the difficulties posed by the amount and density of DNA in the nuclear environment. We propose that the glucocorticoid receptor can search DNA by interdomain transfer. Analogous to Tarzan swinging vine-to-vine, this mechanism envisions receptors transferring between DNA sites without ever dissociating from DNA. A combination of molecular, kinetic and physical approaches will be employed to test this proposal.