A riboswitch-containing sRNA controls gene expression by sequestration of a response regulator

Riboswitches are short segments of RNA that bind small molecules and switch between two different conformations, thereby regulating gene expression (see the Perspective by Chen and Gottesman). DebRoy et al. and Mellin et al. find a new class of riboswitches—in two different species of bacteria—that are both part of and regulate the production of a noncoding RNA. Each riboswitch ensures that a particular metabolic pathway is only activated in the presence of an essential small-molecule cofactor. In the absence of the cofactor, the full-length non-coding RNA is made and binds a regulator protein, preventing the regulator protein from inappropriately activating the metabolic pathway. Science , this issue p. [937][1] and p. [940][2]; see also p. [876][3] [1]: /lookup/doi/10.1126/science.1255091 [2]: /lookup/doi/10.1126/science.1255083 [3]: /lookup/doi/10.1126/science.1258494