Biosynthesis of the translation machinery: identification of regulatory factors and mechanisms

许多与翻译装置相关的哺乳动物蛋白质（核糖体蛋白和延伸因子）的合成在翻译水平上受到有丝分裂和营养信号的选择性调节。相应的mrna的特征是存在一个独特的序列元件，称为5‘末端寡聚嘧啶通道（5’ top），它包含翻译顺式调控元件的核心。TOP mrna的翻译控制表现为在静止细胞或饥饿状态下，它们在分裂细胞时从多聚体选择性和可逆地转变为亚多聚体mRNP颗粒。然而，调节TOP mRNA翻译的机制和相关的交易因子都没有被确定。我们已经建立了纯化TOP基序结合因子的策略，并测试了它们在TOP mrna翻译中的活性。在之前的资助期内获得的数据表明，TOP mRNA翻译需要积极作用的因子，这些因子以磷酸化依赖的方式结合到TOP基序上。确定该因子及其在TOP mRNA调控中的作用模式是本项目的主要任务。

The synthesis of many mammalian proteins associated with the translational apparatus (ribosomal proteins and elongation factors) is selectively regulated at the translational level by mitogenic and nutritional signals. The corresponding mRNAs are characterized by the presence of a unique se-quence element, termed the 5' Terminal OligoPyrimidine tract (5'TOP), which comprises the core of the translational cis-regulatory element. The translational control of TOP mRNAs is manifested by their selective and reversible shift from polysomes in dividing cells into subpolysomal mRNP particles in quiescent cells or upon starvation. However, neither the mechanisms that regulate TOP mRNA trans-lation nor transacting factors involved have been identified. We have established strategies to purify TOP motif-binding factors and to test their activity in translation of TOP mRNAs. Data obtained in the previous funding period suggest that TOP mRNA translation requires positively acting factors, which bind in a phosphorylation-dependent manner to the TOP motif. The identification of this factor and its mode of action in TOP mRNA regulation is the major task of this project.