RESUMO
The prokaryotic Sm-like protein Hfq plays an essential role in the stability and function of trans-encoded small regulatory RNAs in enterobacteria that function in posttranscriptional control by base-pairing with cognate target mRNAs. Hfq associates with both regulatory RNA and target RNA, and its interaction promotes annealing. So far, mutational and structural studies have established that Escherichia coli Hfq contains two separate RNA binding sites that are part of the conserved N-terminal portion of the protein. Moreover, it has been suggested that the nonconserved C-terminal extension of E. coli Hfq might constitute a third RNA interaction surface with specificity for mRNA. However, the role of the C-terminus has not been fully resolved but is clearly important for a complete understanding of Hfq function in posttranscriptional regulation and RNA decay. Here we examined the ability of E. coli Hfq derivatives, consisting of the conserved core and short C-terminal extensions, to support the regulation of rpoS expression and riboregulation by various well-characterized small regulatory RNAs. Our data show that, in all cases tested, the truncated proteins are fully capable of promoting posttranscriptional control, indicating that the C-terminal tail of E. coli Hfq plays a small role or no role in riboregulation.
Assuntos
Proteínas de Escherichia coli/química , Proteínas de Escherichia coli/metabolismo , Fator Proteico 1 do Hospedeiro/química , Fator Proteico 1 do Hospedeiro/metabolismo , Motivos de Aminoácidos , Sequência de Aminoácidos , Proteínas de Bactérias/biossíntese , Proteínas de Bactérias/genética , Sequência de Bases , DNA Glicosilases/genética , DNA Glicosilases/metabolismo , Primers do DNA/genética , Escherichia coli/genética , Escherichia coli/metabolismo , Proteínas de Escherichia coli/genética , Inativação Gênica , Genes Bacterianos , Fator Proteico 1 do Hospedeiro/genética , Modelos Moleculares , Dados de Sequência Molecular , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/genética , Fragmentos de Peptídeos/metabolismo , Conformação Proteica , Estrutura Secundária de Proteína , Processamento Pós-Transcricional do RNA , RNA Bacteriano/genética , RNA Bacteriano/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Fator sigma/biossíntese , Fator sigma/genéticaRESUMO
Small trans-encoded RNAs (sRNAs) modulate the translation and decay of mRNAs in bacteria. In Gram-negative species, antisense regulation by trans-encoded sRNAs relies on the Sm-like protein Hfq. In contrast to this, Hfq is dispensable for sRNA-mediated riboregulation in the Gram-positive species studied thus far. Here, we provide evidence for Hfq-dependent translational repression in the Gram-positive human pathogen Listeria monocytogenes, which is known to encode at least 50 sRNAs. We show that the Hfq-binding sRNA LhrA controls the translation and degradation of its target mRNA by an antisense mechanism, and that Hfq facilitates the binding of LhrA to its target. The work presented here provides the first experimental evidence for Hfq-dependent riboregulation in a Gram-positive bacterium. Our findings indicate that modulation of translation by trans-encoded sRNAs may occur by both Hfq-dependent and -independent mechanisms, thus adding another layer of complexity to sRNA-mediated riboregulation in Gram-positive species.
Assuntos
Regulação Bacteriana da Expressão Gênica , Fator Proteico 1 do Hospedeiro/fisiologia , Listeria monocytogenes/genética , RNA Antissenso/química , RNA não Traduzido/química , Pareamento de Bases , Sequência de Bases , Fator Proteico 1 do Hospedeiro/genética , Fator Proteico 1 do Hospedeiro/metabolismo , Listeria monocytogenes/metabolismo , Dados de Sequência Molecular , Mutação , Iniciação Traducional da Cadeia Peptídica , Biossíntese de Proteínas , Estabilidade de RNA , RNA Antissenso/genética , RNA Mensageiro/química , RNA Mensageiro/metabolismo , RNA não Traduzido/genéticaRESUMO
In Listeria monocytogenes, the alternative sigma factor sigma(B) plays important roles in stress tolerance and virulence. Here, we present the identification of SbrA, a novel small noncoding RNA that is produced in a sigma(B)-dependent manner. This finding adds the sigma(B) regulon to the growing list of stress-induced regulatory circuits that include small noncoding RNAs.