Because RNAs fold as they are being synthesized, their transcription rate can affect their folding. Here, we report the results of single-molecule fluorescence studies that characterize the ligand-dependent cotranscriptional folding of the Escherichia coli thiM riboswitch that regulates translation. We found that the riboswitch aptamer folds into the “off” conformation independent of its ligand, but switches to the “on” conformation during transcriptional pausing near the translational start codon. Ligand binding maintains the riboswitch in the off conformation during transcriptional pauses. We expect our assay will permit the controlled study of the two main physical mechanisms that regulate cotranscriptional folding: transcriptional pausing and transcriptional speed.

中文翻译：

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硫胺素焦磷酸核糖开关的共转录折叠单分子FRET研究

由于RNA在合成时会折叠，因此它们的转录速率会影响其折叠。在这里，我们报告单分子荧光研究的结果，该研究表征了调控翻译的大肠杆菌thiM核糖开关的配体依赖性共转录折叠。我们发现核糖开关适体折叠成独立于其配体的“ off”构象，但是在翻译起始密码子附近的转录暂停过程中切换到“ on”构象。配体结合使核糖开关在转录暂停期间保持关闭构象。我们希望我们的检测方法能够对调节共转录折叠的两个主要物理机制进行受控研究：转录暂停和转录速度。