Eukaryotic gene expression can be spatiotemporally tuned at the post-transcriptional level by cis-regulatory elements in mRNA sequences. An important example is the AU-rich element (ARE), which induces mRNA destabilization in a variety of biological contexts in mammals and can also mediate translational control. Regulation is mediated by trans-acting factors that recognize the ARE, such as Tristetraprolin (TTP) and BRF1/ZFP36L1. Although both proteins can destabilize their target mRNAs through the recruitment of the CCR4-NOT deadenylation complex, TTP also directly regulates translation. Whether ZFP36L1 can directly repress translation remains unknown. Here, we used an in vitro translation system derived from mammalian cell lines to address this key mechanistic issue in ARE regulation by ZFP36L1. Functional assays with mutant proteins reveal that ZFP36L1 can repress translation via AU-Rich elements independent of deadenylation. ZFP36L1-mediated translation repression requires interaction between ZFP36L1 and CNOT1, suggesting that it might use a repression mechanism similar to either TPP or miRISC. However, several lines of evidence suggest that the similarity ends there. Unlike, TTP, it does not efficiently interact with either 4E-HP or GIGYF2, suggesting it does not repress translation by recruiting these proteins to the mRNA cap. Moreover, ZFP36L1 could not repress ECMV-IRES driven translation and was resistant to pharmacological eIF4A inhibitor silvestrol, suggesting fundamental differences with miRISC repression via eIF4A. Collectively, our results reveal that ZFP36L1 represses translation directly and suggest that it does so via a novel mechanism distinct from other translational regulators that interact with the CCR4-NOT deadenylase complex.

中文翻译：

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ARE结合蛋白ZFP36L1与CNOT1相互作用，通过不依赖于腺苷酸化的机制直接抑制翻译。

真核基因表达可在转录后水平通过mRNA序列中的顺式调控元件进行时空调节。一个重要的例子是富含AU的元件（ARE），它在哺乳动物的多种生物学环境中诱导mRNA不稳定，并且还可以介导翻译控制。调节是由识别ARE的反式作用因子介导的，例如Tristetraprolin（TTP）和BRF1 / ZFP36L1。尽管两种蛋白都可以通过募集CCR4-NOT腺苷酸化复合物来破坏其靶标mRNA的稳定性，但TTP也直接调节翻译。ZFP36L1是否可以直接抑制翻译仍然未知。在这里，我们使用了源自哺乳动物细胞系的体外翻译系统，以解决ZFP36L1在ARE调控中的这一关键机制问题。突变蛋白的功能测定表明ZFP36L1可以通过不依赖腺苷酸化的AU-Rich元件抑制翻译。ZFP36L1介导的翻译抑制需要ZFP36L1和CNOT1之间的相互作用，这表明它可能使用类似于TPP或miRISC的抑制机制。但是，有几条证据表明相似性到此为止。与TTP不同，它不能与4E-HP或GIGYF2有效相互作用，表明它不会通过将这些蛋白质募集到mRNA帽来抑制翻译。此外，ZFP36L1不能抑制ECMV-IRES驱动的翻译，并且对药理性eIF4A抑制剂silvestrol具有抗性，表明与通过eIF4A进行miRISC抑制的根本差异。总的来说，