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的合成(核糖体蛋白和延伸因子)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mRNAs的特征是存在一个独特的序列元件，称为5‘末端寡嘧啶链(5’TOP)，它组成了翻译顺式调节元件的核心。顶端mRNAs的翻译控制表现为它们在细胞分裂过程中选择性和可逆地从多聚体转变为静止细胞或饥饿时的亚多聚体mRNP颗粒。然而，无论是调控TOP mRNA转录的机制还是涉及的交易因子都还没有确定。我们已经建立了纯化顶端基序结合因子的策略，并测试它们在顶端mRNAs翻译中的活性。在上一个资助期获得的数据表明，TOP mRNA的翻译需要积极的作用因子，这些因子以磷酸化依赖的方式与顶端基序结合。确定该因子及其在TOP mRNA调控中的作用方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.