REVEALING RIBOSWITCHES: RNA is isolated from bacteria and tagged with a 3’ adapter, to which a complimentary oligonucleotide binds for reverse transcription and sequencing. Sequence analysis then reveals those transcripts that have been fully transcribed versus those prematurely truncated. The reproducible presence of similarly truncated transcripts for a given gene suggests the presence of a riboswitch in the mRNA.© GEORGE RETSECK
Nature has evolved a staggering array of mechanisms for regulating gene expression, but few are so simple and elegant as the riboswitch. These RNA elements sit within the 5’ noncoding regions of bacterial messenger RNAs (mRNA) and regulate an mRNA’s own transcription or translation, depending on the switch’s conformation. In the case of a transcription-regulating riboswitch, for example, association of the switch with a particular ligand, such as a metabolite, can alter the switch’s structure and in turn terminate transcription.
Since the first riboswitches were identified in the early 2000s, “most of the known riboswitches have been discovered pretty much one by one by sequence comparisons,” says RNA expert Thomas Hermann of the University of California, San Diego. But while that approach works well for ...
