RNA, but not protein partners, is directly responsible for translational silencing by a bacterial Hfq-binding small RNA
RNA, but not protein partners, is directly responsible for translational silencing by a bacterial Hfq-binding small RNA
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DOI：
10.1073/pnas.0803106105
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发表时间：
2008-07-29
影响因子：
11.1
通讯作者：
Aiba, Hiroji
中科院分区：
文献类型：
--
作者：
Maki, Kimika;Uno, Kanako;Aiba, Hiroji
SgrS 是一种 Hfq 结合小 RNA，在大肠杆菌中葡萄糖磷酸盐胁迫下被诱导。它与 Hfq 和 RNase E 形成特定的核糖核蛋白复合物，导致编码葡萄糖转运蛋白的 ptsG mRNA 的翻译抑制和快速降解。在这里，我们报告了在确定的体外系统中 ptsG mRNA 的翻译沉默。我们证明 SgrS 和 Hfq 是翻译沉默的最小组成部分，可以在细胞中忠实地重现反应。我们表明，当 ptsG mRNA 在没有 Hfq 帮助的情况下被迫与 SgrS 碱基配对时，ptsG-SgrS 碱基配对足以引起翻译抑制。翻译抑制的程度与双链体形成的程度相关。我们得出结论，碱基配对本身而不是 Hfq 直接负责翻译沉默，并且 Hfq 在基因沉默中的主要作用是刺激 SgrS 和 ptsG mRNA 之间的碱基配对。这种简单的机制与真核生物中 miRNA 的作用形成鲜明对比，在真核生物中，RNA 被认为仅充当蛋白质伙伴的指导。
SgrS is an Hfq-binding small RNA that is induced under glucose phosphate stress in Escherichia coli. It forms a specific ribonucleoprotein complex with Hfq and RNase E resulting in translational repression and rapid degradation of ptsG mRNA, encoding the glucose transporter. Here, we report translational silencing of ptsG mRNA in a defined in vitro system. We demonstrate that SgrS and Hfq are the minimum components for translational silencing to faithfully reproduce the reaction in cells. We show that ptsG-SgrS base pairing is sufficient to cause translational repression when the ptsG mRNA is forced to base pair with SgrS without the help of Hfq. The extent of translational repression correlates with the extent of duplex formation. We conclude that base pairing itself but not Hfq is directly responsible for translational silencing and the major role of Hfq in gene silencing is to stimulate the base pairing between SgrS and ptsG mRNA. This simple mechanism is in striking contrast to miRNA action in eukaryote in which the RNA is believed to act only as a guide of protein partners.