NOVEL CDK2 MECHANISM CONTROLS CELL PROLIFERATION

非转化的T细胞需要IL-2进行增殖，而IL-2 R α是高亲和力生物学相关IL-2 R的必需组分。 许多研究已经表征了促有丝分裂刺激的T细胞中IL-2 R α的转录上调。 另一方面，具有潜在生物学重要性的是，IL-2 R α表达的转录后控制尚未得到充分探索或明确证明。 该提案中提供的数据清楚地表明，在暴露于促有丝分裂刺激的原代T细胞中，IL-2 R α表达在翻译水平上受到调节。 我们表明，增加翻译的IL-2 R α转录是通过诱导IL-2信号通路，我们认为，翻译上调IL-2 R α需要的细胞周期调节激酶，cdk 2的活性。 有趣的是，我们发现cdk 2的表达也在转录后水平上受到控制，并且很可能是通过cdk 2依赖性机制。 这些研究确定了cdk 2的新作用，并表明以前未被识别的机制有助于IL-2 R α和cdk 2的表达。 我们还提出的数据表明，cdk 2激活和IL-2信号是相互依赖的过程中脾T细胞。 我们认为，cdk 2的活性是必需的IL-2 R的有效翻译和IL-2 R产生的信号促进cdk 2激活通过维持下调的cdk 2抑制剂，P27 kip 1。 这些相互作用和cdk 2参与两个重要的细胞周期调节分子- IL-2 R α和cdk 2本身-的翻译形成了我们的建议的重点。具体而言，我们将研究cdk 2活性可能控制原代脾细胞中IL-2 R α翻译的潜在机制。 我们将鉴定负责翻译调控的IL-2 R α mRNA的5'非翻译区，并确定蛋白质是否以依赖于cdk 2活性的方式与该区域结合。 我们还将确定cdk 2活性是否调节cdk 2的合成或稳定性。 另外的实验将评估IL-2信号传导对TCR活化的脾细胞中p27 kip 1持续下调的贡献。 最后，TCR活化促进细胞周期蛋白A表达的机制将被描述。

Nontransformed T cells require IL-2 for proliferation, and IL-2Ralpha is an obligatory component of the high affinity biologically relevant IL-2R. Numerous studies have characterized the transcriptional up-regulation of IL-2Ralpha in mitogenically stimulated T cells. On the other hand, and of potential biological importance, post transcriptional control of IL-2Ralpha expression has yet to be adequately explored or definitively demonstrated. Data presented in this proposal clearly show that IL-2Ralpha expression is regulated at the translational level in primary T cells exposed to mitogenic stimuli. We show that increased translation of the IL-2Ralpha transcript is paralleled by the induction of IL-2 signaling pathways, and we suggest that translational up-regulation of IL-2Ralpha requires the activity of the cell cycle regulatory kinase, cdk2. Interestingly, we found that cdk2 expression was also controlled at a post- transcriptional level and, most likely, by a cdk2-dependent mechanism. These studies identify novel actions of cdk2 and suggest that previously unrecognized mechanisms contribute to the expression of IL-2Ralpha and cdk2. We also present data showing that cdk2 activation and IL-2 signaling are interdependent processes in splenic T cells. We suggest that cdk2 activity is required for the efficient translation of IL-2R and that signals generated by the IL-2R facilitate cdk2 activation by maintaining the down-regulation of the cdk2 inhibitor, P27kip1. These interactions and the involvement of cdk2 in the translation of two important cell cycle regulatory molecules - IL-2Ralpha and cdk2 itself - form the focus of our proposal. Specifically, we will examine potential mechanisms by which cdk2 activity might control the translation of IL-2Ralpha in primary splenocytes. We will identify the region of the 5' untranslated region of the IL-2Ralpha mRNA that is responsible for translational regulation and will determine if proteins bind to this region in a manner dependent on cdk2 activity. We will also determine if cdk2 activity modulates the synthesis or the stability of cdk2. Additional experiments will assess the contribution of IL-2 signaling to the continued down-regulation of p27kip1 in TCR-activated splenocytes. Lastly, the mechanism by which TCR activation promotes the expression of cyclin A will be delineated.