Sequestration of a two-component response regulator by a riboswitch regulated non-coding RNA

Riboswitches are ligand-binding elements contained within the 5’ untranslated regions of bacterial transcripts, which generally regulate expression of downstream open reading frames. Here we show that in Listeria monocytogenes, a Vitamin B12-binding (B12) riboswitch controls expression of a non-coding regulatory RNA, Rli55. Rli55 in turn controls expression of the eut genes, which enable ethanolamine utilization and require B12 as a cofactor. Defects in ethanolamine utilization, or in its regulation by Rli55, significantly attenuate Listeria virulence in mice. Rli55 functions by sequestering the two-component response regulator, EutV via a EutV binding-site contained within the RNA. Thus Rli55 is a riboswitch-regulated member of the small group of regulatory RNAs that function by sequestering a protein and reveals a unique mechanism of signal integration in bacterial gene regulation. Overall design: RNA-Seq and CLIP-Seq to investigate the sequestration of EutV by rli55