Biophysics Laboratories, School of Biological Sciences, Institute of Biomedical and Biomolecular Sciences, University of Portsmouth, Portsmouth, PO1 2DT, United Kingdom.
RNA. 2013 Aug;19(8):1089-104. doi: 10.1261/rna.034595.112. Epub 2013 Jun 26.
OxyS and RprA are two small noncoding RNAs (sRNAs) that modulate the expression of rpoS, encoding an alternative sigma factor that activates transcription of multiple Escherichia coli stress-response genes. While RprA activates rpoS for translation, OxyS down-regulates the transcript. Crucially, the RNA binding protein Hfq is required for both sRNAs to function, although the specific role played by Hfq remains unclear. We have investigated RprA and OxyS interactions with Hfq using biochemical and biophysical approaches. In particular, we have obtained the molecular envelopes of the Hfq-sRNA complexes using small-angle scattering methods, which reveal key molecular details. These data indicate that Hfq does not substantially change shape upon complex formation, whereas the sRNAs do. We link the impact of Hfq binding, and the sRNA structural changes induced, to transcript stability with respect to RNase E degradation. In light of these findings, we discuss the role of Hfq in the opposing regulatory functions played by RprA and OxyS in rpoS regulation.
OxyS 和 RprA 是两种小的非编码 RNA（sRNA），它们调节 rpoS 的表达，rpoS 编码一种替代的σ因子，激活多个大肠杆菌应激反应基因的转录。虽然 RprA 激活 rpoS 进行翻译，但 OxyS 下调转录物。至关重要的是，RNA 结合蛋白 Hfq 是这两种 sRNA 发挥作用所必需的，尽管 Hfq 所起的具体作用仍不清楚。我们使用生化和生物物理方法研究了 RprA 和 OxyS 与 Hfq 的相互作用。特别是，我们使用小角散射方法获得了 Hfq-sRNA 复合物的分子包络，揭示了关键的分子细节。这些数据表明，Hfq 在形成复合物时形状没有明显变化，而 sRNA 则发生了变化。我们将 Hfq 结合的影响以及诱导的 sRNA 结构变化与相对于 RNase E 降解的转录物稳定性联系起来。鉴于这些发现，我们讨论了 Hfq 在 RprA 和 OxyS 在 rpoS 调节中发挥的相反调节功能中的作用。
