Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea.
Mol Cells. 2019 May 31;42(5):426-439. doi: 10.14348/molcells.2019.0040.
Many small RNAs (sRNAs) regulate gene expression by base pairing to their target messenger RNAs (mRNAs) with the help of Hfq in . The sRNA DsrA activates translation of the mRNA in an Hfq-dependent manner, but this activation ability was found to partially bypass Hfq when DsrA is overproduced. The precise mechanism by which DsrA bypasses Hfq is unknown. In this study, we constructed strains lacking all three -activating sRNAs (i.e., ArcZ, DsrA, and RprA) in and backgrounds, and then artificially regulated the cellular DsrA concentration in these strains by controlling its ectopic expression. We then examined how the expression level of was altered by a change in the concentration of DsrA. We found that the translation and stability of the mRNA are both enhanced by physiological concentrations of DsrA regardless of Hfq, but that depletion of Hfq causes a rapid degradation of DsrA and thereby decreases mRNA stability. These results suggest that the observed Hfq dependency of DsrA-mediated activation mainly results from the destabilization of DsrA in the absence of Hfq, and that DsrA itself contributes to the translational activation and stability of the mRNA in an Hfq-independent manner.
许多小 RNA（sRNA）通过与靶信使 RNA（mRNA）碱基配对，在 Hfq 的帮助下调节基因表达。sRNA DsrA 以 Hfq 依赖的方式激活 mRNA 的翻译，但当 DsrA 过量产生时，这种激活能力被发现部分绕过 Hfq。DsrA 绕过 Hfq 的精确机制尚不清楚。在这项研究中，我们构建了在 和 背景下缺乏所有三种 -激活 sRNA（即 ArcZ、DsrA 和 RprA）的菌株，然后通过控制其异位表达来人工调节这些菌株中细胞内 DsrA 的浓度。然后，我们检查了 DsrA 浓度的变化如何改变 的表达水平。我们发现，生理浓度的 DsrA 可增强 的翻译和稳定性，而不依赖于 Hfq，但 Hfq 的耗尽会导致 DsrA 的快速降解，从而降低 mRNA 的稳定性。这些结果表明，观察到的 DsrA 介导的 激活对 Hfq 的依赖性主要归因于 Hfq 缺失时 DsrA 的不稳定性，并且 DsrA 本身以不依赖于 Hfq 的方式促进 的翻译激活和稳定性。
