Base-pair conformational switch modulates miR-34a targeting of Sirt1 mRNA
Base-pair conformational switch modulates miR-34a targeting of Sirt1 mRNA
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DOI：
10.1038/s41586-020-2336-3
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发表时间：
2020-05-27
期刊：
影响因子：
64.8
通讯作者：
Petzold, Katja
中科院分区：
文献类型：
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作者：
Baronti, Lorenzo;Guzzetti, Ileana;Petzold, Katja
MicroRNAs （miRNAs）调节信使rna （mrna）的翻译水平。目前，能够解释靶mRNA的选择和翻译抑制效率的主要参数是miRNA的“种子”区与其对应mRNA之间的碱基配对(1)。在这里，我们使用R-1 rho松弛色散核磁共振(2)和分子模拟(3)揭示了基于miRNA-mRNA双链中单个碱基对重排的动态开关，将弱的五个碱基对种子延长到完整的七个碱基对种子。这种开关还导致种子和补充螺旋的同轴堆叠，适合人类Argonaute 2蛋白（Ago2），让人想起原核Ago的活性状态（4,5）。稳定这一瞬态导致细胞中靶mRNA的抑制增强，揭示了这种miRNA-mRNA结构的重要性。我们的观察结果与之前关于miRNA从最初的“筛选”状态到“激活”状态的逐步靶向过程的研究结果相结合，揭示了RNA双工在Ago2种子之外的作用。同源microRNA对信使RNA的抑制不仅依赖于互补碱基配对，还依赖于单个碱基对的重排，从而产生更适合人类Ago2蛋白的构象。
MicroRNAs (miRNAs) regulate the levels of translation of messenger RNAs (mRNAs). At present, the major parameter that can explain the selection of the target mRNA and the efficiency of translation repression is the base pairing between the 'seed' region of the miRNA and its counterpart mRNA(1). Here we use R-1 rho relaxation-dispersion nuclear magnetic resonance(2) and molecular simulations(3) to reveal a dynamic switch-based on the rearrangement of a single base pair in the miRNA-mRNA duplex-that elongates a weak five-base-pair seed to a complete seven-base-pair seed. This switch also causes coaxial stacking of the seed and supplementary helix fitting into human Argonaute 2 protein (Ago2), reminiscent of an active state in prokaryotic Ago(4,5). Stabilizing this transient state leads to enhanced repression of the target mRNA in cells, revealing the importance of this miRNA-mRNA structure. Our observations tie together previous findings regarding the stepwise miRNA targeting process from an initial 'screening' state to an 'active' state, and unveil the role of the RNA duplex beyond the seed in Ago2.Repression of a messenger RNA by a cognate microRNA depends not only on complementary base pairing, but also on the rearrangement of a single base pair, producing a conformation that fits better within the human Ago2 protein.