Chowdhury Saheli, Maris Christophe, Allain Frédéric H-T, Narberhaus Franz
Institute of Molecular Biology and Biophysics, ETH Zurich, Zürich, Switzerland.
EMBO J. 2006 Jun 7;25(11):2487-97. doi: 10.1038/sj.emboj.7601128. Epub 2006 May 18.
Regulatory RNA elements, like riboswitches, respond to intracellular signals by three-dimensional (3D) conformational changes. RNA thermometers employ a similar strategy to sense temperature changes in the cell and regulate the translational machinery. We present here the first 3D NMR structure of the functional domain of a highly conserved bacterial RNA thermometer containing the ribosome binding site that remains occluded at normal temperatures (30 degrees C). We identified a region adjacent to the Shine-Dalgarno sequence that has a network of weak hydrogen bonds within the RNA helix. With the onset of heat shock at 42 degrees C, destabilisation of the RNA structure initiates at this region and favours the release of the ribosome binding site and of the start codon. Deletion of a highly conserved G residue leads to the formation of a stable regular RNA helix that loses thermosensing ability. Our results indicate that RNA thermometers are able to sense temperature changes without the aid of accessory factors.
调控RNA元件，如核糖开关，通过三维（3D）构象变化对细胞内信号作出反应。RNA温度计采用类似策略来感知细胞内的温度变化并调节翻译机制。我们在此展示了一种高度保守的细菌RNA温度计功能域的首个3D NMR结构，该温度计包含在常温（30摄氏度）下仍被封闭的核糖体结合位点。我们鉴定出一个与Shine-Dalgarno序列相邻的区域，该区域在RNA螺旋内有一个弱氢键网络。随着42摄氏度热休克的开始，RNA结构的不稳定在该区域启动，有利于核糖体结合位点和起始密码子的释放。缺失一个高度保守的G残基会导致形成一个稳定的规则RNA螺旋，从而失去温度感应能力。我们的结果表明，RNA温度计能够在无需辅助因子的情况下感知温度变化。
