MECHANISMS OF TRANSLATION CONTROL DURING APOPTOSIS

细胞凋亡或程序性细胞死亡是一种高度受控的、普遍的细胞过程。 细胞凋亡的失调与几种疾病如癌症有关。 老年痴呆症和亨廷顿舞蹈症。 细胞凋亡的过程诱导翻译关闭，这可能是由某些起始因子的切割和其他调节因子的磷酸化介导的，并且这也可能是完成细胞杀伤的关键。 研究将在体外细胞提取物或纯化的重组蛋白中进行，或在体外组织培养细胞中进行，以阐明翻译调节因子中发生的各种修饰及其在细胞凋亡期间对翻译活性的特定影响。真核生物翻译起始因子4G（eIF 4G）和多聚腺苷酸结合蛋白（PABP）是控制翻译起始速率和调节mRNA末端之间5 '-3'相互作用的关键因子。 提供的初步证据表明，eIF 4G和PABP都在细胞凋亡发展期间蛋白质合成被关闭时被切割。 实验将确定切割是否破坏或调节eIF 4G和PABP在所有或仅一些翻译反应中起作用的能力和/或5 '-3'相互作用是否被破坏。 此外，我们假设其mRNA含有内部核糖体进入位点（IRES）的关键调节蛋白的帽非依赖性翻译将能够在eIF 4G切割后继续翻译. 将在某些病毒和细胞基因上发现的IRES控制元件亚克隆到各种表达载体中，并在各种细胞凋亡或因子切割条件下测试体外和体内的翻译效率。 长期目标是了解细胞凋亡过程中的事件如何导致细胞死亡，并进一步了解人类细胞中蛋白质合成是如何调节的。

Apoptosis or programmed cell death is a highly controlled, universal cellular process of cells. Dysregulation of apoptosis has been linked to several diseases such as cancer. Alzheimers disease and Huntinton's chorea. The process of apoptosis induces translation shutoff which is likely to be mediated by cleavage of certain initiation factors and phosphorylation of other regulatory factors, and which is also likely to be crucial for the completion of cellular killing. Studies will be performed in vitro in cell extracts or with purified recombinant proteins or in vitro in tissue culture cells to elucidate the various modifications which occur in translation regulatory factors and their specific effects on translation activity during apoptosis. Efforts will focus on eukaryotic translation initiation factor 4G (eIF4G) and poly(A)binding protein (PABP) which are crucial factors which control translation initiation rates and modulate 5'-3' interactions between mRNA ends. Preliminary evidence provided shows that both eIF4G and PABP are cleaved at the time during development of apoptosis when protein synthesis is being shutoff in the cells. Experiments will determine if cleavage destroys or modulates the ability of eIF4G and PABP to function in all or only some translation reactions and/or if 5'-3' interactions are disrupted. Further, we hypothesize that cap- independent translation of crucial regulatory proteins whose mRNAs contain internal ribosomal entry sites (IRES) will be capable of continued translation after cleavage of eIF4G. IRES control elements found on certain viral and cellular genes will be subcloned into various expression vectors and tested for translational efficiencies in vitro and in vivo under various conditions of apoptosis or factor-cleavage. The long term goal is to understand how events during apoptosis lead to cell death and further our basic understanding of how protein synthesis is regulated in human cells.