Department of Cell and Molecular Biology, Biomedical Center, Uppsala University, Uppsala, Sweden.
Department of Cell and Molecular Biology, Biomedical Center, Uppsala University, Uppsala, Sweden
EMBO J. 2019 Apr 1;38(7). doi: 10.15252/embj.2018101199. Epub 2019 Mar 4.
Small RNAs post-transcriptionally regulate many processes in bacteria. Base-pairing of sRNAs near ribosome-binding sites in mRNAs inhibits translation, often requiring the RNA chaperone Hfq. In the canonical model, Hfq simultaneously binds sRNAs and mRNA targets to accelerate pairing. Here, we show that the sRNAs OmrA and OmrB inhibit translation of the diguanylate cyclase DgcM (previously: YdaM), a player in biofilm regulation. In OmrA/B repression of , Hfq is not required as an RNA interaction platform, but rather unfolds an inhibitory RNA structure that impedes OmrA/B binding. This restructuring involves distal face binding of Hfq and is supported by RNA structure mapping. A corresponding mutant protein cannot support inhibition and ; proximal and rim mutations have negligible effects. Strikingly, OmrA/B-dependent translational inhibition is restored, in complete absence of Hfq, by a deoxyoligoribonucleotide that base-pairs to the biochemically mapped Hfq site in mRNA We suggest that Hfq-dependent RNA structure remodeling can promote sRNA access, which represents a mechanism distinct from an interaction platform model.
小 RNA 在后转录水平上调节细菌中的许多过程。sRNA 与 mRNA 核糖体结合位点附近的碱基配对抑制翻译，这通常需要 RNA 伴侣 Hfq。在经典模型中，Hfq 同时结合 sRNA 和 mRNA 靶标以加速配对。在这里，我们表明 sRNA OmrA 和 OmrB 抑制二鸟苷酸环化酶 DgcM（以前称为 YdaM）的翻译，DgcM 是生物膜调节中的一个参与者。在 OmrA/B 对 的抑制中，Hfq 不作为 RNA 相互作用平台，而是展开抑制性 RNA 结构，阻碍 OmrA/B 的结合。这种重排涉及 Hfq 的远端面结合，并得到 RNA 结构图谱的支持。相应的突变蛋白不能支持 和 的抑制；近端和边缘突变的影响可以忽略不计。引人注目的是，完全缺乏 Hfq 时，与生物化学图谱中 Hfq 结合位点结合的脱氧寡核苷酸可恢复 OmrA/B 依赖性翻译抑制 。我们认为 Hfq 依赖性 RNA 结构重塑可以促进 sRNA 的进入，这代表了一种与相互作用平台模型不同的机制。
