title: Two antisense RNAs target the transcriptional regulator CsgD to inhibit curli synthesis.
abstract: Escherichia coli produces proteinaceous surface structures called curli that are involved in adhesion and biofilm formation. CsgD is the transcriptional activator of curli genes. We show here that csgD expression is, in part, controlled post-transcriptionally by two redundant small RNAs (sRNAs), OmrA and OmrB. Their overexpression results in curli deficiency, in accordance with the inhibition of chromosomally encoded, FLAG-tagged CsgD. Downregulation of csgD occurs by a direct antisense interaction within the csgD 5'-UTR, far upstream of the ribosome-binding site (RBS). OmrA/B downregulate plasmid-borne csgD-gfp fusions in vivo, and inhibit CsgD translation in vitro. The RNA chaperone Hfq is required for normal csgD mRNA and OmrA/B levels in the cell, and enhances sRNA-dependent inhibition of csgD translation in vitro. Translational inhibition involves two phylogenetically conserved secondary structure modules that are supported by chemical and enzymatic probing. The 5'-most element is necessary and sufficient for regulation, the one downstream comprises the RBS and affects translational efficiency. OmrA/B are two antisense RNAs that regulate a transcription factor to alter a morphotype and group behaviour.
authors.affiliation: Department of Cell and Molecular Biology, Biomedical Center, Uppsala University, Uppsala, Sweden. erik.holmqvist@icm.uu.se
authors.forename: Erik
authors.initials: E
authors.lastname: Holmqvist
authors.forename: Johan
authors.initials: J
authors.lastname: Reimegård
authors.forename: Maaike
authors.initials: M
authors.lastname: Sterk
authors.forename: Nina
authors.initials: N
authors.lastname: Grantcharova
authors.forename: Ute
authors.initials: U
authors.lastname: Römling
authors.forename: Eduard Gerhart Heinrich
authors.initials: EG
authors.lastname: Wagner
mesh_terms: D001665:Binding Sites / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D010957:Plasmids; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D016372:RNA, Antisense / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D022661:RNA, Untranslated / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012270:Ribosomes / Q000235:genetics / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; D011506:Proteins; D016372:RNA, Antisense; D012333:RNA, Messenger; D022661:RNA, Untranslated
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