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

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 Grampositive 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. ARTICLE HISTORY

Novel hypercapsulation RNA thermosensor variants in Neisseria meningitidis and their association with invasive meningococcal disease: a genetic and phenotypic investigation and molecular epidemiological study

“…34 Future molecular epidemiology studies should include other regulatory RNAs, because they are involved in meningococcal pathogenesis and fitness. 7,[35][36][37] In this study, due to low availability of WGS from carrier isolates, we were not able to assert causation between the presence of different RNATs and virulence of the meningococcus. Most meningococcal isolate WGS originates from invasive meningococcal disease cases, as required by national routine surveillance of meningococcal disease.…”

The emerging role of bacterial regulatory RNAs in disease

“…A cis-encoded ncRNA element utilised by the meningococcus is the thiamine pyrophosphate (TPP)-riboswitch [34]. Thiamine is a crucial cofactor for all organisms and can only be biosynthesised in bacteria, fungi, and plants, but not in mammals.…”

“…By using its TPP riboswitch, the meningococcus senses thiamine concentration in its surrounding environment. In turn, the bacterium modulates its gene expressions, where thiC and cytX have been experimentally confirmed, to coordinate production or scavenging of thiamine, facilitating its survival within the nasopharynx [34].…”

Exploring the structure, function of thiamine pyrophosphate riboswitch, and designing small molecules for antibacterial activity

“…(Ahmad et al, 2020; Ali et al, 2010; Antunes et al, 2019; S. Bocobza et al, 2007; S. E. Bocobza & Aharoni, 2014; Croft et al, 2007; Donovan et al, 2018; Yadav et al, 2015; Zhao et al, 2011) Recently, TPP riboswitch in the human pathogen Neisseria meningitides has been characterized. (Righetti et al, 2020) N. meningitides is a Gram‐negative bacterium causing fatal infections such as acute meningitis and septicemia. (Stephens et al, 2007) In this review, we present the structural underpinnings of TPP binding with TPP riboswitch from various experimental and theoretical studies.…”