Characterization of a transcriptional TPP riboswitch in the human pathogen Neisseria meningitidis

RNA Biol. 2020 May;17(5):718-730. doi: 10.1080/15476286.2020.1727188. Epub 2020 Feb 20.

Abstract

Increasing evidence has demonstrated that regulatory RNA elements such as riboswitches (RS) play a pivotal role in the fine-tuning of bacterial gene expression. In this study, we investigated and characterized a novel transcriptional thiamine pyrophosphate (TPP) RS in the obligate human pathogen N. meningitidis MC58 (serogroup B). This RS is located in the 5´ untranslated region upstream of thiC gene, encoding a protein involved in TPP biosynthesis, an essential cofactor for all living beings. Primer extension revealed the transcriptional start site of thiC. Northern blot analysis of thiC mRNA and reporter gene studies confirmed the presence of an active TPP-sensing RS. Expression patterns of the wild-type RS and site-specific mutants showed that it is an OFF switch that controls transcription elongation of thiC mRNA. Interestingly, the regulatory mechanism of the meningococcal thiC RS resembles the Gram-positive Bacillus subtilis thiC RS rather than the Gram-negative Escherichia coli thiC RS. Therefore, the meningococcal thiC RS represents a rare example of transcriptional RS in a Gram-negative bacterium. We further observed that the RS is actively involved in modulating gene expression in response to different growth media and to supplemented bacterial and eukaryotic cell lysates as possible sources of nutrients in the nasopharynx. Our results suggest that RS-mediated gene regulation could influence meningococcal fitness, through the fine-tuning of biosynthesis and scavenging of nutrients and cofactors, such as thiamine.

Keywords: Neisseria meningitidis; RNA; TPP; gene regulation; non-coding RNA; pathogen; regulatory RNA; riboswitch; vitamin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • Gene Expression Regulation, Bacterial*
  • Genes, Reporter
  • Humans
  • Meningococcal Infections / microbiology*
  • Neisseria meningitidis / genetics*
  • Nucleic Acid Conformation
  • RNA Folding
  • RNA, Bacterial / chemistry
  • RNA, Bacterial / genetics
  • Riboswitch*
  • Thiamine Pyrophosphate
  • Transcription, Genetic*

Substances

  • RNA, Bacterial
  • Riboswitch
  • Thiamine Pyrophosphate

Grant support

This work was funded by the Swedish Foundation for Strategic Research [ICA14-0013] and Knut and Alice Wallenberg Foundation [KAW 2014.0177], and the Swedish Research Council [Dnr: 2014-2050].