title: Inter-sigmulon communication through topological promoter coupling.
abstract: Divergent transcription from within bacterial intergenic regions frequently involves promoters dependent on alternative σ-factors. This is the case for the non-overlapping σ70- and σ54-dependent promoters that control production of the substrate-responsive regulator and enzymes for (methyl)phenol catabolism. Here, using an array of in vivo and in vitro assays, we identify transcription-driven supercoiling arising from the σ54-promoter as the mechanism underlying inter-promoter communication that results in stimulation of the activity of the σ70-promoter. The non-overlapping 'back-to-back' configuration of a powerful σ54-promoter and weak σ70-promoter within this system offers a previously unknown means of inter-sigmulon communication that renders the σ70-promoter subservient to signals that elicit σ54-dependent transcription without it possessing a cognate binding site for the σ54-RNA polymerase holoenzyme. This mode of control has the potential to be a prevalent, but hitherto unappreciated, mechanism by which bacteria adjust promoter activity to gain appropriate transcriptional control.
authors.affiliation: Department of Molecular Biology, Umeå University, Umeå SE 90187, Sweden.
authors.forename: Teresa
authors.initials: T
authors.lastname: Del Peso Santos
authors.affiliation: Department of Molecular Biology, Umeå University, Umeå SE 90187, Sweden victoria.shingler@molbiol.umu.se.
authors.forename: Victoria
authors.initials: V
authors.lastname: Shingler
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D015870:Gene Expression; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D009876:Operon; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012808:Sigma Factor / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D012808:Sigma Factor