The environmentally-regulated interplay between local three-dimensional chromatin organisation and transcription ofproVWXinE. coli

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.