One Platform, Five Brands: How Nature Cuts the Cost on Riboswitches

Abstract

Riboswitches regulate gene expression in cis in response to changing metabolite concentrations in cells. Since flavin mononucleotide1,2 and thiamine pyrophosphate1,3 sensing riboswitches were discovered in 2002, more than 20 classes of metabolite-responsive riboswitches have been identified, primarily controlling essential metabolic or virulence genes in bacteria. Riboswitches are typically found in the mRNA 5′ untranslated region where they control expression usually by regulating premature transcription termination or translation initiation. Some riboswitches additionally control mRNA turnover4 or Rho-dependent termination.5 Regardless of their regulatory mechanism, the modular riboswitch structure is composed of an aptamer domain (ligand binding) and an effector domain (regulation). Ligand binding to the aptamer domain stabilizes an alternate structure and induces an effector domain switch to turn gene expression on or off. Riboswitches offer an efficient and rapid means to respond to changing metabolic conditions in a cell.