Walter Nils, Chauvier Adrien, Dandpat Shiba, Romero Rosa
Res Sq. 2024 Jan 29:rs.3.rs-3849447. doi: 10.21203/rs.3.rs-3849447/v1.
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 discovered 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 paradigmatic 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在不断变化的环境中影响细菌锰稳态所需的可靠基因调控。核糖开关——与大多数结构化RNA一样——被认为是共转录折叠的，受到配体结合和转录事件的影响；然而，对于这些过程如何协调以实现稳健调控，人们了解甚少。通过结合单分子和整体方法，我们发现了单个锰离子和被DNA模板序列立即暂停在下游的转录RNA聚合酶（RNAP）如何通过典型核糖开关中的桥接开关螺旋P1.1进行协调。这种协调实现了新生RNA迄今被忽视的半对接全局构象、P1.1碱基对稳定、转录因子NusA排出以及RNAP暂停延长，从而促进转录通读。我们的工作展示了一个核心的、可适应的RNA螺旋如何类似于一级杠杆系统的分子支点发挥作用，整合不同信号以实现精细平衡的基因表达控制。
