Single Molecule Analysis Group and Center for RNA Biomedicine, Department of Chemistry, University of Michigan, Ann Arbor, MI, USA.
Intel Corporation, Hillsboro, OR, USA.
Nat Commun. 2024 May 10;15(1):3955. doi: 10.1038/s41467-024-48409-8.
Widespread manganese-sensing transcriptional riboswitches effect the dependable gene regulation needed for bacterial manganese homeostasis in changing environments. Riboswitches - like most structured RNAs - are believed to fold co-transcriptionally, subject to both ligand binding and transcription events; yet how these processes are orchestrated for robust regulation is poorly understood. Through a combination of single-molecule and bulk approaches, we discover how a single Mn ion and the transcribing RNA polymerase (RNAP), paused immediately downstream by a DNA template sequence, are coordinated by the bridging switch helix P1.1 in the representative Lactococcus lactis riboswitch. This coordination achieves a heretofore-overlooked semi-docked global conformation of the nascent RNA, P1.1 base pair stabilization, transcription factor NusA ejection, and RNAP pause extension, thereby enforcing transcription readthrough. Our work demonstrates how a central, adaptable RNA helix functions analogous to a molecular fulcrum of a first-class lever system to integrate disparate signals for finely balanced gene expression control.
广泛存在的锰感应转录核糖开关影响了细菌在不断变化的环境中维持锰稳态所需的可靠基因调控。与大多数结构 RNA 一样，核糖开关被认为是在共转录过程中折叠的，受到配体结合和转录事件的影响；然而，这些过程是如何协调以实现稳健的调控还知之甚少。通过结合单分子和批量方法，我们发现单个 Mn 离子和正在转录的 RNA 聚合酶（RNAP）如何在代表性的乳球菌乳糖操纵子核糖开关中由桥接开关螺旋 P1.1 协调。这种协调实现了先前被忽视的新生 RNA 的半对接全局构象、P1.1 碱基对稳定、转录因子 NusA 逐出和 RNAP 暂停延伸，从而强制转录通读。我们的工作表明，一个中央、适应性 RNA 螺旋如何类似于一个一级杠杆系统的分子支点，用于整合不同的信号，以实现精细平衡的基因表达控制。
