Analysis of cytoplasmic functions of the exon junction complex

多细胞动物细胞核中含有内含子的转录物的剪接导致外显子连接复合物（EJC）在新生mRNA上的沉积。在细胞质内，EJC是无义介导的mRNA衰变（NMD）的重要标志，并增加剪接mRNA的翻译效率。这两种效应可能通过EJC和翻译机制的共享组件相互关联。我们以前已经确定了一个关键作用的EJC组件BTZ在NMD，并希望进一步阐明其机制的NMD激活。我们将描述由BTZ调控的靶mRNA，并确定调控BTZ NMD功能的相互作用的辅助因子。EJC的翻译刺激功能由EJC相互作用因子SKAR介导。mTOR依赖性激酶S6 K1通过与EJC结合的SKAR的直接蛋白质-蛋白质相互作用被募集，磷酸化mRNP的重要组分，从而刺激结合mRNA的翻译效率。我们的目标是表征分子机制和EJC组件参与这一过程，并确定中央磷酸化mRNP效应蛋白。这些互补项目将共同解决两个重要基因表达过程的机制，这两个过程在EJC水平上是分子联系的。

Splicing of intron containing transcripts in the nucleus of metazoan cells leads to the deposition of exon junction complexes (EJC) on the nascent mRNAs. Within the cytoplasm, EJCs are essential marks for nonsense-mediated mRNA decay (NMD) and increase the translation efficiency of spliced mRNAs. Both effects are likely interconnected by shared components of the EJC and the translational machinery. We have previously identified a critical role of the EJC component BTZ during NMD and want to further elucidate its mechanism of NMD activation. We will characterize target mRNAs regulated by BTZ and identify interacting co-factors that regulate BTZ’s NMD function. The translation stimulation function of the EJC is mediated by the EJC interacting factor SKAR. The mTOR-dependent kinase S6K1 is recruited by a direct protein-protein interaction to EJC-bound SKAR, phosphorylates important components of the mRNP and thereby stimulates the translation efficiency of the bound mRNA. We aim to characterize the molecular mechanism and the EJC components involved in this process and to identify central phosphorylated mRNP effector proteins. Together, these complementary projects will address the mechanism of two important gene expression processes that are molecularly linked at the level of the EJC.