Post-transcriptional gene regulation by an Hfq-independent small RNA in Caulobacter crescentus. Author Kathrin Fröhlich, Konrad Förstner, Zemer Gitai Publication Year 2018 Type Journal Article Abstract Bacterial small RNAs (sRNAs) are a heterogeneous group of post-transcriptional regulators that often act at the heart of large networks. Hundreds of sRNAs have been discovered by genome-wide screens and most of these sRNAs exert their functions by base-pairing with target mRNAs. However, studies addressing the molecular roles of sRNAs have been largely confined to gamma-proteobacteria, such as Escherichia coli. Here we identify and characterize a novel sRNA, ChvR, from the alpha-proteobacterium Caulobacter crescentus. Transcription of chvR is controlled by the conserved two-component system ChvI-ChvG and it is expressed in response to DNA damage, low pH, and growth in minimal medium. Transient over-expression of ChvR in combination with genome-wide transcriptome profiling identified the mRNA of the TonB-dependent receptor ChvT as the sole target of ChvR. Genetic and biochemical analyses showed that ChvR represses ChvT at the post-transcriptional level through direct base-pairing. Fine-mapping of the ChvR-chvT interaction revealed the requirement of two distinct base-pairing sites for full target regulation. Finally, we show that ChvR-controlled repression of chvT is independent of the ubiquitous RNA-chaperone Hfq, and therefore distinct from previously reported mechanisms employed by prototypical bacterial sRNAs. These findings have implications for the mechanism and evolution of sRNA function across bacterial species. Keywords Gene Expression Regulation, Bacterial, Base Sequence, Gene Expression Profiling, Bacterial Proteins, Nucleic Acid Conformation, RNA, Bacterial, RNA, Messenger, RNA, Small Untranslated, Protein Binding, Models, Molecular, Base Pairing, Host Factor 1 Protein, DNA Damage, Caulobacter crescentus Journal Nucleic Acids Res Volume 46 Issue 20 Pages 10969-10982 Date Published 2018 Nov 16 ISSN Number 1362-4962 DOI 10.1093/nar/gky765 Alternate Journal Nucleic Acids Res PMCID PMC6237742 PMID 30165530 PubMedPubMed CentralGoogle ScholarBibTeXEndNote X3 XML