Department of Bacteriology, University of Wisconsin-Madison, 1550 Linden Dr., Madison, WI 53706, USA.
Microbiology (Reading). 2010 Dec;156(Pt 12):3791-3800. doi: 10.1099/mic.0.043992-0. Epub 2010 Sep 9.
6S RNA is a small, non-coding RNA that interacts directly with σ(70)-RNA polymerase and regulates transcription at many σ(70)-dependent promoters. Here, we demonstrate that 6S RNA regulates transcription of relA, which encodes a ppGpp synthase. The 6S RNA-dependent regulation of relA expression results in increased ppGpp levels during early stationary phase in cells lacking 6S RNA. These changes in ppGpp levels, although modest, are sufficient to result in altered regulation of transcription from σ(70)-dependent promoters sensitive to ppGpp, including those promoting expression of genes involved in amino acid biosynthesis and rRNA. These data place 6S RNA as another player in maintaining appropriate gene expression as cells transition into stationary phase. Independent of this ppGpp-mediated 6S RNA-dependent regulation, we also demonstrate that in later stationary phase, 6S RNA continues to downregulate transcription in general, and specifically at a subset of the amino acid promoters, but through a mechanism that is independent of ppGpp and which we hypothesize is through direct regulation. In addition, 6S RNA-dependent regulation of σ(S) activity is not mediated through observed changes in ppGpp levels. We suggest a role for 6S RNA in modulating transcription of several global regulators directly, including relA, to downregulate expression of key pathways in response to changing environmental conditions.
6S RNA 是一种小的非编码 RNA，它直接与 σ(70)-RNA 聚合酶相互作用，并调节许多 σ(70)-依赖启动子的转录。在这里，我们证明 6S RNA 调节 relA 的转录，relA 编码 ppGpp 合酶。在缺乏 6S RNA 的细胞中，6S RNA 依赖性调节 relA 表达导致早期稳定期 ppGpp 水平增加。尽管这些 ppGpp 水平的变化适度，但足以导致对 σ(70)-依赖启动子的转录调节发生改变，这些启动子对 ppGpp 敏感，包括促进参与氨基酸生物合成和 rRNA 的基因表达的启动子。这些数据将 6S RNA 定位为另一个在细胞进入稳定期时维持适当基因表达的参与者。与这种 ppGpp 介导的 6S RNA 依赖性调节无关，我们还证明在后期稳定期，6S RNA 继续下调总体转录，特别是在一组氨基酸启动子上，但通过一种不依赖于 ppGpp 的机制，我们假设这是通过直接调节。此外，6S RNA 对 σ(S) 活性的调节不是通过观察到的 ppGpp 水平变化介导的。我们提出 6S RNA 在调节几个全局调节剂的转录中发挥作用，包括 relA，以响应环境条件的变化下调关键途径的表达。
