Riboswitches are specialized RNA molecules that help bacteria regulate gene activity. These molecules can change their shape in response to specific chemicals, allowing them to turn genes on or off when needed. Scientists have learned a great deal about the sensing regions of riboswitches, called aptamer domains, but understanding the rest of the molecule has been more challenging because of the tremendous sequence diversity found in their expression platforms.

Researchers from Northwestern University have now developed a new strategy to study entire riboswitch sequences instead of focusing only on their sensing regions.

The team developed a computational and experimental workflow that extends riboswitch sequences beyond the aptamer domain and identifies those containing intrinsic transcription terminators. These filtered sequences were then used to generate evolutionary covariation models that reveal how different parts of the RNA work together.

To establish the approach, the researchers analyzed 1,901 fluoride riboswitch sequences. They combined high-throughput in vitro transcription experiments with next-generation sequencing to identify patterns of coordinated sequence changes that support the known mechanism of fluoride sensing and gene regulation.

The investigators then expanded the analysis to additional riboswitch classes, including ZTP, lysine, and thiamine pyrophosphate (TPP) riboswitches. In each case, the resulting models supported mechanisms that had been proposed previously, providing additional confidence in how these RNA molecules operate.

Riboswitches are valuable model systems because they undergo dynamic structural rearrangements to perform biological functions. Understanding these changes is important because RNA structures play key roles in gene regulation and cellular adaptation.

The new methodology provides a way to analyze large numbers of complete riboswitch sequences and examine how RNA structures evolve over time. By capturing interactions between sensing domains and expression platforms, the approach offers a more complete picture of how riboswitches function and may help researchers better understand RNA dynamics across many biological systems.