Makraki Eleni, Miliara Sophia, Pagkalos Michalis, Kokkinidis Michael, Mylonas Efstratios, Fadouloglou Vasiliki E
Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas (IMBB-FORTH), Heraklion, Greece.
Department of Biology, University of Crete, Heraklion, Greece.
Front Mol Biosci. 2023 Jul 17;10:1219668. doi: 10.3389/fmolb.2023.1219668. eCollection 2023.
The non-coding 6S RNA is a master regulator of the cell cycle in bacteria which binds to the RNA polymerase-σ holoenzyme during the stationary phase to inhibit transcription from the primary σ factor. Inhibition is reversed upon outgrowth from the stationary phase by synthesis of small product RNA transcripts (pRNAs). 6S and its complex with a pRNA were structurally characterized using Small Angle X-ray Scattering. The 3D models of 6S and 6S:pRNA complex presented here, demonstrate that the fairly linear and extended structure of 6S undergoes a major conformational change upon binding to pRNA. In particular, 6S:pRNA complex formation is associated with a compaction of the overall 6S size and an expansion of its central domain. Our structural models are consistent with the hypothesis that the resultant particle has a shape and size incompatible with binding to RNA polymerase-σ. Overall, by use of an optimized methodological approach, especially useful for structural studies, our study considerably improves our understanding of the structural basis of 6S regulation by offering a mechanistic glimpse of the 6S transcriptional control.
非编码6S RNA是细菌细胞周期的主要调节因子，在稳定期它与RNA聚合酶-σ全酶结合，以抑制初级σ因子的转录。当从稳定期生长出来时，通过合成小的产物RNA转录本（pRNAs），抑制作用被逆转。利用小角X射线散射对6S及其与pRNA的复合物进行了结构表征。这里展示的6S和6S:pRNA复合物的三维模型表明，6S相当线性且伸展的结构在与pRNA结合时会发生重大构象变化。特别是，6S:pRNA复合物的形成与6S整体尺寸的压缩及其中心结构域的扩展有关。我们的结构模型与这样的假设一致，即所得颗粒的形状和大小与结合RNA聚合酶-σ不相容。总体而言，通过使用一种优化的方法，这种方法对结构研究特别有用，我们的研究通过提供对6S转录控制机制的一瞥，极大地增进了我们对6S调控结构基础的理解。
