title: Unexpected properties of sRNA promoters allow feedback control via regulation of a two-component system.
abstract: Two-component systems (TCS) and small regulatory RNAs (sRNAs) are both widespread regulators of gene expression in bacteria. TCS are in most cases transcriptional regulators. A large class of sRNAs act as post-transcriptional regulators of gene expression that modulate the translation and/or stability of target-mRNAs. Many connections have been recently unraveled between these two types of regulators, resulting in mixed regulatory circuits with poorly characterized properties. This study focuses on the negative feedback circuit that exists between the EnvZ-OmpR TCS and the OmrA/B sRNAs. We have shown that OmpR directly activates transcription from the omrA and omrB promoters, allowing production of OmrA/B sRNAs that target multiple mRNAs, including the ompR-envZ mRNA. This control of ompR-envZ by the Omr sRNAs does not affect the amount of phosphorylated OmpR, i.e. the presumably active form of the regulator. Accordingly, expression of robust OmpR targets, such as the ompC or ompF porin genes, is not affected by OmrA/B. However, we find that several OmpR targets, including OmrA/B themselves, are sensitive to changing total OmpR levels. As a result, OmrA/B limit their own synthesis. These findings unravel an additional layer of control in the expression of some OmpR targets and suggest the existence of differential regulation within the OmpR regulon.
authors.affiliation: CNRS UMR8261, Associated with University Paris Diderot, Sorbonne Paris Cité, Institut de Biologie Physico-Chimique, 75005 Paris, France.
authors.forename: Anaïs
authors.initials: A
authors.lastname: Brosse
authors.affiliation: CNRS UMR8261, Associated with University Paris Diderot, Sorbonne Paris Cité, Institut de Biologie Physico-Chimique, 75005 Paris, France.
authors.forename: Anna
authors.initials: A
authors.lastname: Korobeinikova
authors.affiliation: Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Susan
authors.initials: S
authors.lastname: Gottesman
authors.affiliation: CNRS UMR8261, Associated with University Paris Diderot, Sorbonne Paris Cité, Institut de Biologie Physico-Chimique, 75005 Paris, France maude.guillier@ibpc.fr.
authors.forename: Maude
authors.initials: M
authors.lastname: Guillier
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005809:Genes, Regulator; D008954:Models, Biological; D009154:Mutation; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012329:RNA, Bacterial / Q000235:genetics*; D058727:RNA, Small Untranslated / Q000235:genetics*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D012329:RNA, Bacterial; D058727:RNA, Small Untranslated; D015534:Trans-Activators