Transcriptional riboswitches involve RNA aptamers that are typically found in the 5′ untranslated regions (UTRs) of bacterial mRNAs and form alternative secondary structures upon binding to cognate ligands. Alteration of the riboswitch's secondary structure results in perturbations of an adjacent expression platform that controls transcription elongation and termination, thus turning downstream gene expression “on” or “off.” Riboswitch ligands are typically small metabolites, divalent cations, anions, signaling molecules, or other RNAs, and can be part of larger signaling cascades. The interconnectedness of ligand binding, RNA folding, RNA transcription, and gene expression empowers riboswitches to integrate cellular processes and environmental conditions across multiple timescales. For a successful response to an environmental cue that may determine a bacterium's chance of survival, a coordinated coupling of timescales from microseconds to minutes must be achieved. This review focuses on recent advances in our understanding of how riboswitches affect such critical gene expression control across time.

转录核糖开关涉及通常存在于细菌 mRNA 的 5' 非翻译区 (UTR) 中的 RNA 适体，并在与同源配体结合后形成替代的二级结构。核糖开关二级结构的改变会导致控制转录延伸和终止的相邻表达平台的扰动，从而“打开”或“关闭”下游基因表达。核糖开关配体通常是小的代谢物、二价阳离子、阴离子、信号分子或其他RNA，并且可以是更大的信号级联的一部分。配体结合、RNA 折叠、RNA 转录和基因表达的相互关联性使核糖开关能够跨多个时间尺度整合细胞过程和环境条件。为了成功地响应可能决定细菌生存机会的环境线索，必须实现从微秒到分钟的时间尺度的协调耦合。这篇综述重点关注我们对核糖开关如何随时间影响这种关键基因表达控制的理解的最新进展。