CYCLOSPORINE AND GENE EXPRESSION BY HUMAN THYMOCYTES

本建议的目的是阐明该机制 环孢素（CsA）的作用。 环孢菌素通过抑制 组织特异性基因的激活， 通过用试剂激活胸腺细胞和T细胞， 启动部分已知的转导信号级联。 的 例如环孢菌素的药物的作用机制 特异性抑制基因的表达， 在胸腺细胞或T细胞活化过程中协同表达， 细胞可以通过使用旨在识别和 表征顺式作用DNA序列（识别元件） 是真核生物基因调控所必需的。 已知的转录 几个可诱导的组织特异性基因的因子是预先存在的 并且在激活过程中被转录后修饰， 不需要蛋白质合成的机制;而 另一些则需要新合成的蛋白质来诱导它们的 表情 积极和消极的调节因素， 已经鉴定了对细胞外因子应答的功能。 我的工作假设是CsA可以抑制 编码淋巴因子的基因，要么直接，要么通过与DNA结合 与调节蛋白协同作用，或通过影响 修饰一个或多个推定的调节蛋白（这 修饰可以是共价的或变构的），或通过 影响调节蛋白与“CsA调节蛋白”的结合 基因上的“序列”。 我的目标是找出 胸腺细胞抵抗CsA的作用，因为它已经被 提出一种特定的T细胞亚群对 CsA CsA对未诱导的和诱导后的小鼠肝癌细胞的作用比较 诱导的胸腺细胞将有助于理解 在诱导过程中引发并被抑制的分子事件 关于CsA 环孢霉素A对信号转导级联反应的影响 引起的细胞外诱导剂和它的影响，Ca+2也将 被研究。

The objective of this proposal is the elucidation of the mechanism of action of cyclosporine (CsA). Cyclosporine acts by inhibiting the activation of tissue specific genes which can be induced in vitro by activating thymocytes and T-cells with agents which initiate a partially known cascade of transducing signals. The mechanism of action of a drug such as cyclosporine which specifically inhibits the expression of genes which are coordinately expressed during the activation of thymocytes or T- cells can be analysed by using approaches aimed at identifying and characterizing cis-acting DNA sequences (recognition elements) required for eukaryotic gene regulation. The known transcription factors of several inducible tissue-specific genes are preexisting and are modified during activation by a posttranscriptional mechanism which does not require protein synthesis; whereas others require newly synthesized proteins to induce their expression. Positive and negative regulatory elements which function in response to extracellular agents have been identified. It is my working hypothesis, that CsA can inhibit the induction of genes coding for lymphokines either directly, by binding to DNA in concert with a regulatory protein, or indirectly by affecting the modification of one or more putative, regulatory proteins (this modification can be either covalent or allosteric), or by influencing the binding of regulatory proteins to "CsA regulatory sequences" on the gene. My goal is to identify subsets of thymocytes resistant to the effects of CsA since it has been proposed that a specific subset of T-cells is relatively resistant to CsA. The comparison of the effects of CsA on uninduced and induced thymocytes will be useful for the understanding of the molecular events which are elicited during induction and inhibited by CsA. The effect of CsA on the cascade of transducing signals elicited by extracellular inducers and its effect on Ca+2 will also be studied.