Translational control of ERK signalling pathway by the mRNA cap-binding protein 4EHP. Translational control of ERK signalling pathway by the mRNA cap-binding protein 4EHP

microRNA (miRNA)-mediated gene silencing is commonly deregulated in a wide variety of diseases. Therefore, a better understanding of how miRNAs govern the translation and stability of mRNAs is of paramount importance. We recently demonstrated that the cap-binding protein 4EHP is recruited by the miRNA machinery to effect translational repression. However, the impact of 4EHP on regulation of endogenous mRNAs and its role in cell biology is debated. Herein, using the ribosome profiling assay, we identify a subset of endogenous mRNAs that are sensitive to translational repression by 4EHP. We show that expression of DUSP6, a phosphatase that reverses ERK1/2 phosphorylation, is regulated by 4EHP. This regulation, which occurs exclusively at the level of mRNA translation, without affecting the stability of Dusp6 mRNA, is engendered through 4EHP- and miRNA-dependent elements in Dusp6 3´UTR. Consequently, 4EHP protein controls ERK1/2 phosphorylation, promotes cell growth and inhibits apoptosis. Our data reveal a crucial role for translational control mechanisms in the regulation of the ERK pathway. Overall design: Ribosome profiling and mRNA-seq in 4EHP KO and WT MEFs.

microRNA (miRNA)介导的基因沉默在多种疾病中普遍发生失调。因此，深入理解miRNA如何调控mRNA的翻译与稳定性至关重要。本研究团队近期证实，miRNA调控复合物可招募帽结合蛋白4EHP以介导翻译抑制。然而，4EHP对内源mRNA的调控效应及其在细胞生物学中的功能仍存在学术争议。本研究通过核糖体谱分析（ribosome profiling assay），鉴定出一批对4EHP介导的翻译抑制敏感的内源mRNA。研究发现，可逆转ERK1/2磷酸化的磷酸酶DUSP6的表达受4EHP调控。该调控仅发生于mRNA翻译层面，且不影响Dusp6 mRNA的稳定性，其实现依赖于Dusp6基因3'非翻译区（3'UTR）中4EHP与miRNA依赖的调控元件。因此，4EHP蛋白可调控ERK1/2的磷酸化水平，促进细胞增殖并抑制细胞凋亡。本研究数据揭示了翻译调控机制在ERK信号通路调控中的关键作用。整体实验设计：对4EHP敲除（KO）与野生型（WT）小鼠胚胎成纤维细胞（mouse embryonic fibroblasts, MEFs）开展核糖体谱分析与mRNA测序（mRNA-seq）。