Translational Regulation by the TNF Alpha AU-rich Element

TNF α是一种促炎细胞因子，由几种细胞类型响应感染或损伤而瞬时产生。TNF α的产生在转录、mRNA降解和翻译水平上受到严格调节，并且这种有效分子的异常表达与自身免疫性疾病、类风湿性关节炎、克罗恩病和其它炎性病症有关。TNF α的翻译调节由位于mRNA的3 '-UTR中的富含AU的元件（战神）介导。ARE参与静息细胞中的翻译抑制以及刺激条件下的翻译激活。已经鉴定了几种ARE结合蛋白，其中TIA-1和TIAR与翻译抑制有关。然而，参与TNF α翻译上调的因素尚不清楚。在酵母Saccharomyces cerevisiae中已经开发了用于研究这种现象的系统。ARE结合蛋白Tristetraprolin（TTP）的酵母同源物和TIA-1/TIAR的酵母同源物被发现是ARE翻译调节的关键介质。本研究的目的是利用酵母系统来表征TNF α ARE的翻译调控机制，并进行遗传筛选以鉴定反式作用的TNF α ARE。 精确调节所需的因素。此外，还将研究TTP及其鼠同系物（Tis 11 B和Tis 11 d）在调节小鼠巨噬细胞中TNF α翻译中的作用。这里描述的实验旨在增加我们对一般ARE功能和TNF α表达调控的理解。

TNFalpha is a pro-inflammatory cytokine produced transiently by several cell types in response to infection or injury. Production of TNFalpha is tightly regulated at the levels of transcription, mRNA decay and translation and aberrant expression of this potent molecule has been linked to autoimmune disorders, rheumatoid arthritis, Crohn's disease and other inflammatory conditions. The translational regulation of TNFalpha is mediated by AU-rich elements (AREs) located in the 3'-UTR of the mRNA. The ARE is involved in translational repression in resting cells as well as in activation of translation under stimulatory conditions. Several ARE-binding proteins have been identified and, of these, TIA-1 and TIAR have been implicated in translational repression. However, the factors involved in up-regulation of TNFalpha translation are not known. A system for studying this phenomenon has been developed in the yeast Saccharomyces cerevisiae. The yeast homologues of the ARE-binding protein Tristetraprolin (TTP) and a yeast homologue of TIA-1/TIAR were found to be key mediators of translation regulation by the ARE. The goals of this proposal are to utilize the yeast system to characterize the mechanism of translational regulation by the TNFalpha ARE, and to perform a genetic screen to identify the trans-acting factors required for accurate regulation. In addition, the role of TTP and its murine homologues (Tis 11 b and Tis 11 d) in modulating TNFalpha translation in mouse macrophages will be investigated. The experiments described here aim to increase our understanding of both general ARE function and regulation of TNFalpha expression.