Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, P R China.
Nucleic Acids Res. 2013 Jun;41(11):5938-48. doi: 10.1093/nar/gkt276. Epub 2013 Apr 19.
The rpoS mRNA, which encodes the master regulator σ(S) of general stress response, requires Hfq-facilitated base pairing with DsrA small RNA for efficient translation at low temperatures. It has recently been proposed that one mechanism underlying Hfq action is to bridge a transient ternary complex by simultaneously binding to rpoS and DsrA. However, no structural evidence of Hfq simultaneously bound to different RNAs has been reported. We detected simultaneous binding of Hfq to rpoS and DsrA fragments. Crystal structures of AU6A•Hfq•A7 and Hfq•A7 complexes were resolved using 1.8- and 1.9-Å resolution, respectively. Ternary complex has been further verified in solution by NMR. In vivo, activation of rpoS translation requires intact Hfq, which is capable of bridging rpoS and DsrA simultaneously into ternary complex. This ternary complex possibly corresponds to a meta-stable transition state in Hfq-facilitated small RNA-mRNA annealing process.
rpoS mRNA 编码普遍应激反应的主要调控因子 σ(S)，需要 Hfq 促进与 DsrA 小 RNA 进行碱基配对，才能在低温下进行有效的翻译。最近有人提出，Hfq 作用的一种机制是通过同时结合 rpoS 和 DsrA 来桥接瞬时三元复合物。然而，目前尚未报道 Hfq 同时结合不同 RNA 的结构证据。我们检测到 Hfq 同时结合 rpoS 和 DsrA 片段。使用分别为 1.8 和 1.9 Å 的分辨率解析了 AU6A•Hfq•A7 和 Hfq•A7 复合物的晶体结构。通过 NMR 进一步验证了三元复合物在溶液中的存在。在体内，rpoS 翻译的激活需要完整的 Hfq，它能够同时将 rpoS 和 DsrA 桥接成三元复合物。这种三元复合物可能对应于 Hfq 促进小 RNA-mRNA 退火过程中的亚稳态过渡态。
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