Human 4E-T is an eIF4E-binding protein (4E-BP) present in processing (P)-bodies that represses translation and regulates decay of mRNAs destabilized by AU-rich elements and microRNAs (miRNAs). However, the underlying regulatory mechanisms are still unclear. Here, we show that upon mRNA binding 4E-T represses translation and promotes deadenylation via the recruitment of the CCR4–NOT deadenylase complex. The interaction with CCR4–NOT is mediated by previously uncharacterized sites in the middle region of 4E-T. Importantly, mRNA decapping and decay are inhibited by 4E-T and the deadenylated target is stored in a repressed form. Inhibition of mRNA decapping requires the interaction of 4E-T with the cap-binding proteins eIF4E/4EHP. We further show that regulation of decapping by 4E-T participates in mRNA repression by the miRNA effector protein TNRC6B and that 4E-T overexpression interferes with tristetraprolin (TTP)- and NOT1-mediated mRNA decay. Thus, we postulate that 4E-T modulates 5′-to-3′ decay by swapping the fate of a deadenylated mRNA from complete degradation to storage. Our results provide insight into the mechanism of mRNA storage that controls localized translation and mRNA stability in P-bodies.

中文翻译：

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4E-T结合的mRNA以沉默和去甲腺苷酸化形式存储。

人4E-T是存在于加工（P）体内的eIF4E结合蛋白（4E-BP），可抑制翻译并调节被富含AU的元素和microRNA（miRNA）破坏的mRNA的降解。但是，基本的监管机制仍不清楚。在这里，我们显示了mRNA结合后4E-T通过CCR4-NOT腺苷酸酶复合物的募集抑制翻译并促进腺苷酸化。与CCR4-NOT的相互作用是由4E-T中间区域以前未鉴定的位点介导的。重要的是，4E-T抑制了mRNA的去盖和衰减，并且去烯基化的靶标以抑制的形式存储。抑制mRNA脱盖需要4E-T与帽结合蛋白eIF4E / 4EHP相互作用。我们进一步表明，通过4E-T脱盖的调节参与了miRNA效应蛋白TNRC6B的mRNA抑制，并且4E-T的过表达干扰了tristetraprolin（TTP）-和NOT1介导的mRNA衰减。因此，我们假设4E-T通过将去甲烯基化的mRNA的命运从完全降解转移到存储来调节5'至3'的衰变。我们的研究结果提供了对mRNA储存机制的深入了解，该机制控制了P体内的局部翻译和mRNA稳定性。