Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
Nucleic Acids Res. 2011 May;39(9):3806-19. doi: 10.1093/nar/gkq1219. Epub 2011 Jan 17.
A number of bacterial small RNAs (sRNAs) act as global regulators of stress responses by controlling expression of multiple genes. The sRNA SgrS is expressed in response to glucose-phosphate stress, a condition associated with disruption of glycolytic flux and accumulation of sugar-phosphates. SgrS has been shown to stimulate degradation of the ptsG mRNA, encoding the major glucose transporter. This study demonstrates that SgrS regulates the genes encoding the mannose and secondary glucose transporter, manXYZ. Analysis of manXYZ mRNA stability and translation in the presence and absence of SgrS indicate that manXYZ is regulated by SgrS under stress conditions and when SgrS is ectopically expressed. In vitro footprinting and in vivo mutational analyses showed that SgrS base pairs with manXYZ within the manX coding sequence to prevent manX translation. Regulation of manX did not require the RNase E degradosome complex, suggesting that the primary mechanism of regulation is translational. An Escherichia coli ptsG mutant strain that is manXYZ(+) experiences stress when exposed to the glucose analogs α-methyl glucoside or 2-deoxyglucose. A ptsG manXYZ double mutant is resistant to the stress, indicating that PTS transporters encoded by both SgrS targets are involved in taking up substrates that cause stress.
许多细菌小 RNA（sRNA）通过控制多个基因的表达来充当应激反应的全局调节剂。sRNA SgrS 响应葡萄糖-磷酸应激而表达，这种情况与糖酵解通量的破坏和糖磷酸的积累有关。已经表明，SgrS 可刺激编码主要葡萄糖转运蛋白的 ptsG mRNA 的降解。本研究表明，SgrS 调节编码甘露糖和次级葡萄糖转运蛋白 manXYZ 的基因。在存在和不存在 SgrS 的情况下分析 manXYZ mRNA 的稳定性和翻译表明，在应激条件下和当 SgrS 异位表达时，manXYZ 受 SgrS 调节。体外足迹分析和体内突变分析表明，SgrS 在 manX 编码序列内与 manXYZ 碱基配对，以阻止 manX 翻译。manX 的调节不需要 RNase E 降解酶复合物，这表明主要的调节机制是翻译。暴露于葡萄糖类似物 α-甲基葡萄糖苷或 2-脱氧葡萄糖时，大肠杆菌 ptsG 突变株会经历应激，而 manXYZ(+)ptsG 双突变株对这种应激具有抗性，表明由两个 SgrS 靶标编码的 PTS 转运蛋白参与摄取引起应激的底物。
