Department of Biochemistry, Max Planck Institute for Developmental Biology, Spemannstrasse 35, D-72076 Tübingen, Germany.
Nucleic Acids Res. 2013 Jan;41(2):978-94. doi: 10.1093/nar/gks1078. Epub 2012 Nov 21.
Animal miRNAs silence the expression of mRNA targets through translational repression, deadenylation and subsequent mRNA degradation. Silencing requires association of miRNAs with an Argonaute protein and a GW182 family protein. In turn, GW182 proteins interact with poly(A)-binding protein (PABP) and the PAN2-PAN3 and CCR4-NOT deadenylase complexes. These interactions are required for the deadenylation and decay of miRNA targets. Recent studies have indicated that miRNAs repress translation before inducing target deadenylation and decay; however, whether translational repression and deadenylation are coupled or represent independent repressive mechanisms is unclear. Another remaining question is whether translational repression also requires GW182 proteins to interact with both PABP and deadenylases. To address these questions, we characterized the interaction of Drosophila melanogaster GW182 with deadenylases and defined the minimal requirements for a functional GW182 protein. Functional assays in D. melanogaster and human cells indicate that miRNA-mediated translational repression and degradation are mechanistically linked and are triggered through the interactions of GW182 proteins with PABP and deadenylases.
动物 miRNAs 通过翻译抑制、脱腺苷酸化和随后的 mRNA 降解来沉默 mRNA 靶标。沉默需要 miRNAs 与 Argonaute 蛋白和 GW182 家族蛋白结合。反过来，GW182 蛋白与 poly(A)-结合蛋白 (PABP) 和 PAN2-PAN3 和 CCR4-NOT 脱腺苷酸酶复合物相互作用。这些相互作用是 miRNA 靶标脱腺苷酸化和降解所必需的。最近的研究表明，miRNAs 在诱导靶标脱腺苷酸化和降解之前抑制翻译；然而，翻译抑制和脱腺苷酸化是否偶联或代表独立的抑制机制尚不清楚。另一个悬而未决的问题是，翻译抑制是否也需要 GW182 蛋白与 PABP 和脱腺苷酸酶相互作用。为了解决这些问题，我们表征了果蝇 GW182 与脱腺苷酸酶的相互作用，并确定了功能性 GW182 蛋白的最小要求。在果蝇和人细胞中的功能测定表明，miRNA 介导的翻译抑制和降解在机制上是相关的，并且通过 GW182 蛋白与 PABP 和脱腺苷酸酶的相互作用触发。
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