Riboswitch regulation of gene expression in bacteria

Riboswitches are metabolite-sensing RNA structures that reside primarily within the 5'-untranslated region (5'-UTR) of certain messenger RNAs. These RNA switches have been identified in all three kingdoms of life and are associated with genes whose protein products are required for the manipulation or utilization of the target metabolite. Herein we report that these highly conserved RNA domains found in bacteria serve as genetic control elements that respond to the target metabolite with remarkably high affinity and specificity. Riboswitches appear to regulate the expression of more than 70 genes in B. subtilis accounting for nearly 2% of its genome. These findings indicate that direct interaction between small metabolites and RNA is a significant and widespread form of genetic regulation in bacteria.