Abstract
AbstractNucleoid associated proteins (NAPs) maintain the architecture of bacterial chromosomes and regulate gene expression. Thus, their role as transcription factors may involve three-dimensional chromosome re-organisation. While this model is supported by in vitro studies, direct in vivo evidence is lacking. Here, we use RT-qPCR and 3C-qPCR to study the transcriptional and architectural profiles of the H-NS-regulated, osmoresponsiveproVWXoperon ofEscherichia coliat different osmolarities and provide in vivo evidence for transcription regulation by NAP-mediated chromosome re-modelling in bacteria. We show that activation ofproVWXin response to a hyperosmotic shock involves the destabilization of H-NS-mediated bridges anchored between theproVWXdownstream and upstream regulatory elements (DRE and URE), and between the DRE andygaYthat lies immediately downstream ofproVWX. The re-establishment of these bridges upon adaptation to hyperosmolarity represses the operon. H-NS and H-NS-like proteins are wide-spread amongst bacteria, suggesting that chromosome re-modelling may be a typical feature of transcriptional control in bacteria.
Publisher
Cold Spring Harbor Laboratory