riboregulator

Riboregulators are RNA molecules that regulate gene expression without encoding proteins. They act through base-pairing interactions or structural changes in RNA to influence transcription, translation, or RNA stability. Riboregulators are found in bacteria and archaea, and in some contexts eukaryotes, where they function as noncoding regulators of gene expression.

The main families are small regulatory RNAs (sRNAs), antisense RNAs, and riboswitches. sRNAs typically regulate target mRNAs by base-pairing to affect translation initiation or mRNA decay, often with the help of the Hfq chaperone. Antisense RNAs are transcribed from the opposite strand and pair with the sense mRNA to influence its translation or stability. Riboswitches are structured RNA elements usually located in the 5' untranslated region that bind specific ligands and undergo conformational changes that alter transcription termination or the accessibility of the ribosome binding site.

Riboregulators respond to a variety of cellular cues, including metabolites, temperature, and ions, enabling rapid post-transcriptional control without new protein synthesis.

In bacteria, examples include the sRNAs RyhB and SgrS, which modulate iron usage and glucose-phosphate stress, respectively, by repressing or activating target mRNAs.

In synthetic biology, engineered riboregulators such as toehold switches provide programmable gene control in response to RNA or small-molecule inputs, enabling custom sensors and gene circuits.

While diverse, riboregulators share the property of acting at the RNA level to influence gene expression, offering versatile layers of regulation in natural and engineered systems.