Post-transcriptional gene regulation by an Hfq-independent small RNA in Caulobacter crescentus

Nucleic Acids Res. 2018 Nov 16;46(20):10969-10982. doi: 10.1093/nar/gky765.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / genetics*
  • Bacterial Proteins / metabolism
  • Base Pairing
  • Base Sequence
  • Caulobacter crescentus / genetics*
  • Caulobacter crescentus / metabolism
  • DNA Damage
  • Gene Expression Profiling
  • Gene Expression Regulation, Bacterial*
  • Host Factor 1 Protein / genetics*
  • Host Factor 1 Protein / metabolism
  • Models, Molecular
  • Nucleic Acid Conformation
  • Protein Binding
  • RNA, Bacterial / chemistry
  • RNA, Bacterial / genetics*
  • RNA, Bacterial / metabolism
  • RNA, Messenger / chemistry
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • RNA, Small Untranslated / chemistry
  • RNA, Small Untranslated / genetics*
  • RNA, Small Untranslated / metabolism

Substances

  • Bacterial Proteins
  • Host Factor 1 Protein
  • RNA, Bacterial
  • RNA, Messenger
  • RNA, Small Untranslated