RESUMO
The multicopy sRNA LhrC of the intracellular pathogen Listeria monocytogenes has been shown to be induced under infection-relevant conditions, but its physiological role and mechanism of action is not understood. In an attempt to pinpoint the exact terms of LhrC expression, cell envelope stress could be defined as a specific inducer of LhrC. In this process, the two-component system LisRK was shown to be indispensable for expression of all five copies of LhrC. lapB mRNA, encoding a cell wall associated protein that was recently identified as an important virulence factor, was disclosed to be directly bound by LhrC leading to an impediment of its translation. Although LhrC binds to Hfq, it does not require the RNA chaperone for stability or lapB mRNA interaction. The mechanism of LhrC-lapB mRNA binding was shown to involve three redundant CU-rich sites and a structural rearrangement in the sRNA. This study represents an extensive depiction of a so far uncharacterized multicopy sRNA and reveals interesting new aspects concerning its regulation, virulence association and mechanism of target binding.
Assuntos
Adesinas Bacterianas/genética , Regulação Bacteriana da Expressão Gênica , Listeria monocytogenes/genética , RNA Bacteriano/metabolismo , Pequeno RNA não Traduzido/metabolismo , Adesinas Bacterianas/metabolismo , Dosagem de Genes , Listeria monocytogenes/metabolismo , Listeria monocytogenes/patogenicidade , RNA Bacteriano/genética , RNA Bacteriano/fisiologia , RNA Mensageiro/metabolismo , Pequeno RNA não Traduzido/genética , Pequeno RNA não Traduzido/fisiologia , Estresse Fisiológico , Virulência/genéticaRESUMO
The Gram-positive bacterium Listeria monocytogenes is widely distributed in the environment and capable of causing food-borne infections in susceptible individuals. In this study, we investigated the cell envelope stress response in L. monocytogenes. Whole-genome transcriptional profiling was performed to investigate the response upon exposure to the cell wall antibiotic cefuroxime. Differential expression (at least twofold) of 558 genes was observed, corresponding to 20â% of the L. monocytogenes genome. The majority of genes that were strongly induced by cefuroxime exposure have cell-envelope-related functions, including the dlt operon and the gene encoding penicillin-binding protein PBPD2. A large overlap was observed between the cefuroxime stimulon and genes known to be induced in L. monocytogenes in blood and during intracellular infection, indicating that the cell envelope stress response is active at various stages of the infectious process. We analysed the roles of the two-component systems LisRK and CesRK in the cell envelope response, showing that activation of the most highly cefuroxime-induced genes was LisR- and CesR-dependent. In addition, multiple VirRS- and LiaSR-regulated genes were found to be induced in response to cefuroxime exposure. In total, 53â% of the genes upregulated at least fourfold by cefuroxime exposure are under positive control by one of the four two-component systems. Using genetic analyses, we showed that several genes of the cefuroxime stimulon contribute to the innate resistance of L. monocytogenes to cefuroxime and tolerance to other cell-envelope-perturbing conditions. Collectively, these findings demonstrate central roles for two-component systems in orchestrating the cell envelope stress response in L. monocytogenes.
Assuntos
Proteínas de Bactérias/metabolismo , Cefuroxima/farmacologia , Parede Celular/fisiologia , Listeria monocytogenes/fisiologia , Proteínas Quinases/metabolismo , Fatores de Transcrição/metabolismo , Ampicilina/farmacologia , Proteínas de Bactérias/genética , Sítios de Ligação , Perfilação da Expressão Gênica , Regulação Bacteriana da Expressão Gênica , Gentamicinas/farmacologia , Listeria monocytogenes/genética , Listeria monocytogenes/metabolismo , Testes de Sensibilidade Microbiana , Proteínas Quinases/genética , Deleção de Sequência , Fatores de Transcrição/genética , TranscriptomaRESUMO
The two-component system CesRK of Listeria monocytogenes responds to cell wall-acting antibiotics. We show here that CesRK controls the transcription of several cell envelope-related genes. The CesRK-dependent induction of these genes may be viewed as an attempt by L. monocytogenes to protect itself against the damaging effects of cell wall-acting antibiotics.
