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The influence of exoribonucleases in the regulation of stress related small RNAs
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De modo a poder colonizar um ser humano, a bactéria Escherichia coli tem de ser capaz de resistir tanto a condições de anaerobiose como a um pH de 2. Como resultado directo desta pressão selectiva, e de modo a permitir uma adaptação eficiente em ambientes instáveis, várias redes de regulação genética emergiram. Entre estas, a regulação pós-transcricional é crucial. Baseada nas acções concertadas de tanto as ribonucleases como dos sRNAs esta rede de regulação permite que a célula altere o seu programa genético de forma rápida e eficiente.
Neste trabalho determinámos como é que as exoribonucleases de E. coli (RNase II, RNase R e PNPase) e a proteína Hfq influenciam as vias de resposta a ambientes acídicos e anaeróbios. De facto, descobrirmos que a RNase II parece ser essencial no mecanismo geral de resposta ao choque acídico, com as células deficientes em RNase II a parar o seu crescimento após este. Determinámos ainda que tanto a RNase II como a Hfq são essênciais à expressão do sRNA ArrS, envolvido na adaptação a ambientes acídicos. Surpreendentemente, descobrimos também que tanto no mutante da RNase II como no da RNase R, o sRNA FnrS é expresso em condições aeróbias. Até hoje, este sRNA apenas tinha sido detectado em ambiente anaeróbio.
Neste trabalho mostramos que a RNase II é mais versátil do que previamente pensado, assumindo um lugar de destaque na regulação pós-transcricional da adaptação a ambientes ácidos. Demonstrámos também que tanto a RNase II como a RNase R estão envolvidas na regulação das vias respiratórias celulares. Curiosamente, revelamos ainda que a PNPase, considerada a principal exoribonuclease na degradação de sRNAs, não parece afectar o ArrS e FnrS. Com este trabalho, contribuímos para a compreensão dos mecanismos regulatórios responsaveis pela adaptação a condições de stress em E. coli.
Escherichia coli must be able to withstand anaerobic conditions and pH as low as 2 for several hours when it colonises a human. As a consequence of this selective pressure, and in order to be able to survive in such rapid changing environments, complex networks of genetic regulation have emerged. Post-transcriptional regulatory mechanisms are crucial in bacterial adaptation. Based on the concerted actions of both the ribonucleases and the sRNAs, these regulatory networks allow the cell to quickly and efficiently change their genetic programs. In this work, we determined how the E. coli exoribonucleases (RNase II, RNase R and PNPase) and the Hfq RNA chaperone influence the cellular anaerobic and acidic response pathways. We discovered that RNase II appears to be essential in the general acid shock response mechanism, with RNase II deficient cells indefinitely stopping their growth after acid shock. Moreover, we report that both RNase II and Hfq are required for the expression of the acid related sRNA ArrS. Surprisingly, we also discovered that in the RNase II and, to a lesser extent, in the RNase R mutant strains, the anaerobically induced sRNA FnrS is highly expressed in aerobic conditions. Until now, the expression of this sRNA had only been observed in an anaerobic environment. In this work, we demonstrate that RNase II is more versatile than previous thought, being a crucial post-transcriptional regulator in the adaptation to low pH environments. Furthermore, we also demonstrated that RNase II and RNase R are involved in the regulation of the respiratory pathways. Curiously, we also show that PNPase, considered the main exoribonuclease involved in sRNA degradation, does not influence either the ArrS or FnrS sRNAs. With this work, we improved our understanding on the regulatory mechanism that contribute to stress adaptation in E. coli.
Escherichia coli must be able to withstand anaerobic conditions and pH as low as 2 for several hours when it colonises a human. As a consequence of this selective pressure, and in order to be able to survive in such rapid changing environments, complex networks of genetic regulation have emerged. Post-transcriptional regulatory mechanisms are crucial in bacterial adaptation. Based on the concerted actions of both the ribonucleases and the sRNAs, these regulatory networks allow the cell to quickly and efficiently change their genetic programs. In this work, we determined how the E. coli exoribonucleases (RNase II, RNase R and PNPase) and the Hfq RNA chaperone influence the cellular anaerobic and acidic response pathways. We discovered that RNase II appears to be essential in the general acid shock response mechanism, with RNase II deficient cells indefinitely stopping their growth after acid shock. Moreover, we report that both RNase II and Hfq are required for the expression of the acid related sRNA ArrS. Surprisingly, we also discovered that in the RNase II and, to a lesser extent, in the RNase R mutant strains, the anaerobically induced sRNA FnrS is highly expressed in aerobic conditions. Until now, the expression of this sRNA had only been observed in an anaerobic environment. In this work, we demonstrate that RNase II is more versatile than previous thought, being a crucial post-transcriptional regulator in the adaptation to low pH environments. Furthermore, we also demonstrated that RNase II and RNase R are involved in the regulation of the respiratory pathways. Curiously, we also show that PNPase, considered the main exoribonuclease involved in sRNA degradation, does not influence either the ArrS or FnrS sRNAs. With this work, we improved our understanding on the regulatory mechanism that contribute to stress adaptation in E. coli.
Descrição
Palavras-chave
Microbiologia médica Bacteriologia Genética Escherichia coli Regulação pós-transcricional Exoribonucleases
Contexto Educativo
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Editora
Instituto de Higiene e Medicina Tropical