Institute of Molecular Biology and Biotechnology (IMBB), Foundation for Research and Technology Hellas (FoRTH), 70013 Heraklio, Crete, Greece.
Curr Biol. 2013 Aug 19;23(16):1579-84. doi: 10.1016/j.cub.2013.06.041. Epub 2013 Aug 1.
Noncoding RNAs have recently emerged as important regulators of mRNA translation and turnover [1, 2]. Nevertheless, we largely ignore how their function integrates with protein-mediated translational regulation. We focus on Bicoid, a key patterning molecule in Drosophila, which inhibits the translation of caudal in the anterior part of the embryo [3, 4]. Previous work showed that Bicoid recruits the cap-binding protein d4EHP on the caudal mRNA to repress translation [5]. Here we show that miR-2 family microRNAs are essential cofactors in the repression of caudal. Using an in vivo sensor, we demonstrate that Bicoid acts through a 63 nt response element in the caudal 3' UTR that includes a single miR-2 target site. Mutating that site abolishes Bicoid-mediated repression, and this effect can be partly reversed by expressing a microRNA with compensatory changes that restore binding to the mutated target. Four predicted Bicoid splice isoforms are capable of caudal repression, including two that lack the d4EHP interaction domain; all four isoforms require the microRNA target for repression. The synergy between Bicoid and microRNAs appears to have evolved recently in the context of the drosophilid caudal BRE. The discovery that microRNAs play an essential role in Bicoid-mediated translational repression opens up new perspectives on Bicoid's function and evolution.
非编码 RNA 最近已成为调节 mRNA 翻译和周转的重要调控因子 [1,2]。然而，我们在很大程度上忽略了它们的功能如何与蛋白质介导的翻译调控整合。我们专注于 Bicoid，这是果蝇中一个关键的模式分子，它抑制胚胎前区尾部的翻译 [3,4]。先前的工作表明，Bicoid 招募帽结合蛋白 d4EHP 到尾部 mRNA 上，抑制翻译 [5]。在这里，我们表明 miR-2 家族 microRNAs 是尾部抑制的重要辅助因子。使用体内传感器，我们证明 Bicoid 通过尾部 3'UTR 中的 63 个核苷酸响应元件发挥作用，该元件包含一个单一的 miR-2 靶位点。突变该位点会消除 Bicoid 介导的抑制作用，而通过表达具有补偿性变化的 microRNA 来恢复与突变靶标的结合，可以部分逆转这种抑制作用。四种预测的 Bicoid 剪接异构体都能够抑制尾部，其中两种缺乏 d4EHP 相互作用域；所有四种异构体都需要 microRNA 靶标来进行抑制。Bicoid 和 microRNAs 之间的协同作用似乎是在果蝇尾部 BRE 的背景下最近进化而来的。microRNAs 在 Bicoid 介导的翻译抑制中发挥重要作用的发现，为 Bicoid 的功能和进化提供了新的视角。
