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Maturation of atypical ribosomal RNA precursors in Helicobacter pylori.

ABSTRACT: In most bacteria, ribosomal RNA is transcribed as a single polycistronic precursor that is first processed by RNase III. This double-stranded specific RNase cleaves two large stems flanking the 23S and 16S rRNA mature sequences, liberating three 16S, 23S and 5S rRNA precursors, which are further processed by other ribonucleases. Here, we investigate the rRNA maturation pathway of the human gastric pathogen Helicobacter pylori. This bacterium has an unusual arrangement of its rRNA genes, the 16S rRNA gene being separated from a 23S-5S rRNA cluster. We show that RNase III also initiates processing in this organism, by cleaving two typical stem structures encompassing 16S and 23S rRNAs and an atypical stem-loop located upstream of the 5S rRNA. Deletion of RNase III leads to the accumulation of a large 23S-5S precursor that is found in polysomes, suggesting that it can function in translation. Finally, we characterize a cis-encoded antisense RNA overlapping the leader of the 23S-5S rRNA precursor. We present evidence that this antisense RNA interacts with this precursor, forming an intermolecular complex that is cleaved by RNase III. This pairing induces additional specific cleavages of the rRNA precursor coupled with a rapid degradation of the antisense RNA.

SUBMITTER: Iost I

PROVIDER: S-EPMC6582327 | biostudies-literature | 2019 Jun

REPOSITORIES: biostudies-literature

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Maturation of atypical ribosomal RNA precursors in Helicobacter pylori.

Iost Isabelle I Chabas Sandrine S Darfeuille Fabien F

Nucleic acids research 20190601 11

In most bacteria, ribosomal RNA is transcribed as a single polycistronic precursor that is first processed by RNase III. This double-stranded specific RNase cleaves two large stems flanking the 23S and 16S rRNA mature sequences, liberating three 16S, 23S and 5S rRNA precursors, which are further processed by other ribonucleases. Here, we investigate the rRNA maturation pathway of the human gastric pathogen Helicobacter pylori. This bacterium has an unusual arrangement of its rRNA genes, the 16S ...[more]

PMID: 31006803

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Project description:BackgroundClarithromycin (CLR) is the most commonly recommended antibiotic in Helicobacter pylori eradication regimens, but the prevalence of CLR-resistant H. pylori is increasing. CLR resistance is associated with mutations in the 23S rRNA gene. However, H. pylori eradication can still be achieved with triple therapy, and an additive effect may occur with multiple antibiotics.MethodsTwenty-six CLR-resistant strains were examined. The MIC of clarithromycin was determined by agar-dilution-testing on Columbia agar, as described elsewhere. The conserved region of the H. pylori 23S rRNA gene between nucleotide positions 1445 and 2846 [GenBank: U27270] was amplified. RFLP and sequence analysis were performed with the 1402-bp PCR product. Synergy between clarithromycin and amoxicillin was assessed using the agar dilution checkerboard technique. To confirm the correlation between mutation and synergistic effect with subinhibitory concentrations of AMX, site-directed mutagenesis was performed in four CLR-susceptible H. pylori isolates.ResultsTwenty-six clarithromycin-resistant strains were examined. The conserved region of the H. pylori 23S rRNA gene was amplified, and the purified PCR product was checked for mutations by restriction fragment length polymorphism (RFLP) analysis and sequencing. A synergistic effect was found in only three of the 12 H. pylori strains (25%) with the A2142G mutation and five of the 10 H. pylori strains (50%) with the A2143G mutation (fractional inhibitory concentration: FIC < 0.5, minimal inhibitory concentration: MIC<2 mg/L) was found. Site-directed mutagenesis was performed in four CLR-susceptible H. pylori isolates.Three of these isolates harboring a mutation in position A2143G grew under selection with CLR (MIC >16 mg/L), and all three strains showed the synergistic effect (FIC<0.5). In contrast, three of the same four strains transformed with DNA fragments with a mutation in position A2142G were resistant to CLR (MIC>16 mg/L) and showed no synergism with amoxicillin (FIC>2).ConclusionsHere we demonstrate that in 100% of the in vitro transformed strains, a mutation at position A2143G leads to a synergistic effect between clarithromycin and amoxicillin, whereas a mutation at position at A2142G had no discernible effect.

Project description:Helicobacter pylori (H. pylori) classified as a class I carcinogen by the World Health Organization (WHO) plays an important role in the progression of chronic gastritis and the development of gastric cancer. A major bioactive component of Evodia rutaecarpa, evodiamine, has been known for its anti-bacterial effect and anti-cancer effects. However, the inhibitory effect of evodiamine against H. pylori is not yet known and the inhibitory mechanisms of evodiamine against gastric cancer cells are yet to be elucidated concretely. In this study, therefore, anti-bacterial effect of evodiamine on H. pylori growth and its inhibitory mechanisms as well as anti-inflammatory effects and its mechanisms of evodiamine on H. pylori-induced inflammation were investigated in vitr. Results of this study showed the growth of the H. pylori reference strains and clinical isolates were inhibited by evodiamine. It was considered one of the inhibitory mechanisms that evodiamine downregulated both gene expressions of replication and transcription machineries of H. pylori. Treatment of evodiamine also induced downregulation of urease and diminished translocation of cytotoxin-associated antigen A (CagA) and vacuolating cytotoxin A (VacA) proteins into gastric adenocarcinoma (AGS) cells. This may be resulted from the reduction of CagA and VacA expressions as well as the type IV secretion system (T4SS) components and secretion system subunit protein A (SecA) protein which are involved in translocation of CagA and VacA into host cells, respectively. In particular, evodiamine inhibited the activation of signaling proteins such as the nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) and the mitogen-activated protein kinase (MAPK) pathway induced by H. pylori infection. It consequently might contribute to reduction of interleukin (IL)-8 production in AGS cells. Collectively, these results suggest anti-bacterial and anti-inflammatory effects of evodiamine against H. pylori.

Dataset Information

Maturation of atypical ribosomal RNA precursors in Helicobacter pylori.

Publications

Maturation of atypical ribosomal RNA precursors in Helicobacter pylori.

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