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Role of RpoS in Regulating Stationary Phase Salmonella Typhimurium Pathogenesis-Related Stress Responses under Physiological Low Fluid Shear Force Conditions. mSphere 2022; 7:e0021022. [PMID: 35913142 PMCID: PMC9429890 DOI: 10.1128/msphere.00210-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The discovery that biomechanical forces regulate microbial virulence was established with the finding that physiological low fluid shear (LFS) forces altered gene expression, stress responses, and virulence of the enteric pathogen Salmonella enterica serovar Typhimurium during the log phase. These log phase LFS-induced phenotypes were independent of the master stress response regulator, RpoS (σS). Given the central importance of RpoS in regulating stationary-phase stress responses of S. Typhimurium cultured under conventional shake flask and static conditions, we examined its role in stationary-phase cultures grown under physiological LFS. We constructed an isogenic rpoS mutant derivative of wild-type S. Typhimurium and compared the ability of these strains to survive in vitro pathogenesis-related stresses that mimic those encountered in the infected host and environment. We also compared the ability of these strains to colonize (adhere, invade, and survive within) human intestinal epithelial cell cultures. Unexpectedly, LFS-induced resistance of stationary-phase S. Typhimurium cultures to acid and bile salts stresses did not rely on RpoS. Likewise, RpoS was dispensable for stationary-phase LFS cultures to adhere to and survive within intestinal epithelial cells. In contrast, the resistance of these cultures to challenges of oxidative and thermal stresses, and their invasion into intestinal epithelial cells was influenced by RpoS. These findings expand our mechanistic understanding of how physiological fluid shear forces modulate stationary-phase S. Typhimurium physiology in unexpected ways and provide clues into microbial mechanobiology and nuances of Salmonella responses to microenvironmental niches in the infected host. IMPORTANCE Bacterial pathogens respond dynamically to a variety of stresses in the infected host, including physical forces of fluid flow (fluid shear) across their surfaces. While pathogens experience wide fluctuations in fluid shear during infection, little is known about how these forces regulate microbial pathogenesis. This is especially important for stationary-phase bacterial growth, which is a critical period to understand microbial resistance, survival, and infection potential, and is regulated in many bacteria by the general stationary-phase stress response protein RpoS. Here, we showed that, unlike conventional culture conditions, several stationary-phase Salmonella pathogenic stress responses were not impacted by RpoS when bacteria were cultured under fluid shear conditions relevant to those encountered in the intestine of the infected host. These findings offer new insight into how physiological fluid shear forces encountered by Salmonella during infection might impact pathogenic responses in unexpected ways that are relevant to their disease-causing ability.
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Alipov AA, Lekontseva NV, Mikhailina AO, Fando MS, Tishchenko SV, Nikulin AD. Structure of a Mutant Form of Translation Regulator Hfq with the Extended Loop L4. CRYSTALLOGR REP+ 2021. [DOI: 10.1134/s1063774521050023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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3
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Sonnleitner E, Wulf A, Campagne S, Pei XY, Wolfinger MT, Forlani G, Prindl K, Abdou L, Resch A, Allain FHT, Luisi BF, Urlaub H, Bläsi U. Interplay between the catabolite repression control protein Crc, Hfq and RNA in Hfq-dependent translational regulation in Pseudomonas aeruginosa. Nucleic Acids Res 2019; 46:1470-1485. [PMID: 29244160 PMCID: PMC5815094 DOI: 10.1093/nar/gkx1245] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Accepted: 12/01/2017] [Indexed: 12/23/2022] Open
Abstract
In Pseudomonas aeruginosa the RNA chaperone Hfq and the catabolite repression control protein (Crc) act as post-transcriptional regulators during carbon catabolite repression (CCR). In this regard Crc is required for full-fledged Hfq-mediated translational repression of catabolic genes. RNAseq based transcriptome analyses revealed a significant overlap between the Crc and Hfq regulons, which in conjunction with genetic data supported a concerted action of both proteins. Biochemical and biophysical approaches further suggest that Crc and Hfq form an assembly in the presence of RNAs containing A-rich motifs, and that Crc interacts with both, Hfq and RNA. Through these interactions, Crc enhances the stability of Hfq/Crc/RNA complexes, which can explain its facilitating role in Hfq-mediated translational repression. Hence, these studies revealed for the first time insights into how an interacting protein can modulate Hfq function. Moreover, Crc is shown to interfere with binding of a regulatory RNA to Hfq, which bears implications for riboregulation. These results are discussed in terms of a working model, wherein Crc prioritizes the function of Hfq toward utilization of favored carbon sources.
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Affiliation(s)
- Elisabeth Sonnleitner
- Department of Microbiology, Immunobiology and Genetics, Max F. Perutz Laboratories, University of Vienna, Vienna Biocenter, Dr. Bohrgasse 9, 1030 Vienna, Austria
| | - Alexander Wulf
- Biophysical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Sébastien Campagne
- Institute of Molecular Biology and Biophysics, ETH Zürich, 8093 Zürich, Switzerland
| | - Xue-Yuan Pei
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
| | - Michael T Wolfinger
- Institute of Theoretical Chemistry, University of Vienna, 1090 Vienna, Austria.,Center for Anatomy and Cell Biology, Medical University of Vienna, 1090 Vienna, Austria
| | - Giada Forlani
- Department of Microbiology, Immunobiology and Genetics, Max F. Perutz Laboratories, University of Vienna, Vienna Biocenter, Dr. Bohrgasse 9, 1030 Vienna, Austria
| | - Konstantin Prindl
- Department of Microbiology, Immunobiology and Genetics, Max F. Perutz Laboratories, University of Vienna, Vienna Biocenter, Dr. Bohrgasse 9, 1030 Vienna, Austria
| | - Laetitia Abdou
- Department of Fundamental Microbiology, University of Lausanne, 1015 Lausanne, Switzerland
| | - Armin Resch
- Department of Microbiology, Immunobiology and Genetics, Max F. Perutz Laboratories, University of Vienna, Vienna Biocenter, Dr. Bohrgasse 9, 1030 Vienna, Austria
| | - Frederic H-T Allain
- Institute of Molecular Biology and Biophysics, ETH Zürich, 8093 Zürich, Switzerland
| | - Ben F Luisi
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
| | - Henning Urlaub
- Biophysical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany.,Bioanalytics, Institute for Clinical Chemistry, University Medical Center Göttingen, 37075 Göttingen, Germany
| | - Udo Bläsi
- Department of Microbiology, Immunobiology and Genetics, Max F. Perutz Laboratories, University of Vienna, Vienna Biocenter, Dr. Bohrgasse 9, 1030 Vienna, Austria
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4
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Altuvia Y, Bar A, Reiss N, Karavani E, Argaman L, Margalit H. In vivo cleavage rules and target repertoire of RNase III in Escherichia coli. Nucleic Acids Res 2019; 46:10380-10394. [PMID: 30113670 PMCID: PMC6212723 DOI: 10.1093/nar/gky684] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 07/18/2018] [Indexed: 12/02/2022] Open
Abstract
Bacterial RNase III plays important roles in the processing and degradation of RNA transcripts. A major goal is to identify the cleavage targets of this endoribonuclease at a transcriptome-wide scale and delineate its in vivo cleavage rules. Here we applied to Escherichia coli grown to either exponential or stationary phase a tailored RNA-seq-based technology, which allows transcriptome-wide mapping of RNase III cleavage sites at a nucleotide resolution. Our analysis of the large-scale in vivo cleavage data substantiated the established cleavage pattern of a double cleavage in an intra-molecular stem structure, leaving 2-nt-long 3′ overhangs, and refined the base-pairing preferences in the cleavage site vicinity. Intriguingly, we observed that the two stem positions between the cleavage sites are highly base-paired, usually involving at least one G-C or C-G base pair. We present a clear distinction between intra-molecular stem structures that are RNase III substrates and intra-molecular stem structures randomly selected across the transcriptome, emphasizing the in vivo specificity of RNase III. Our study provides a comprehensive map of the cleavage sites in both intra-molecular and inter-molecular duplex substrates, providing novel insights into the involvement of RNase III in post-transcriptional regulation in the bacterial cell.
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Affiliation(s)
- Yael Altuvia
- Department of Microbiology and Molecular Genetics, Institute for Medical Research Israel-Canada, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem 9112102, Israel
| | - Amir Bar
- Department of Microbiology and Molecular Genetics, Institute for Medical Research Israel-Canada, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem 9112102, Israel
| | - Niv Reiss
- Department of Microbiology and Molecular Genetics, Institute for Medical Research Israel-Canada, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem 9112102, Israel
| | - Ehud Karavani
- Department of Microbiology and Molecular Genetics, Institute for Medical Research Israel-Canada, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem 9112102, Israel
| | - Liron Argaman
- Department of Microbiology and Molecular Genetics, Institute for Medical Research Israel-Canada, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem 9112102, Israel
| | - Hanah Margalit
- Department of Microbiology and Molecular Genetics, Institute for Medical Research Israel-Canada, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem 9112102, Israel
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5
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Kim W, Choi JS, Kim D, Shin D, Suk S, Lee Y. Mechanisms for Hfq-Independent Activation of rpoS by DsrA, a Small RNA, in Escherichia coli. Mol Cells 2019; 42:426-439. [PMID: 31085808 PMCID: PMC6537650 DOI: 10.14348/molcells.2019.0040] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Accepted: 03/11/2019] [Indexed: 01/08/2023] Open
Abstract
Many small RNAs (sRNAs) regulate gene expression by base pairing to their target messenger RNAs (mRNAs) with the help of Hfq in Escherichia coli. The sRNA DsrA activates translation of the rpoS mRNA in an Hfq-dependent manner, but this activation ability was found to partially bypass Hfq when DsrA is overproduced. The precise mechanism by which DsrA bypasses Hfq is unknown. In this study, we constructed strains lacking all three rpoS-activating sRNAs (i.e., ArcZ, DsrA, and RprA) in hfq+ and Hfq- backgrounds, and then artificially regulated the cellular DsrA concentration in these strains by controlling its ectopic expression. We then examined how the expression level of rpoS was altered by a change in the concentration of DsrA. We found that the translation and stability of the rpoS mRNA are both enhanced by physiological concentrations of DsrA regardless of Hfq, but that depletion of Hfq causes a rapid degradation of DsrA and thereby decreases rpoS mRNA stability. These results suggest that the observed Hfq dependency of DsrA-mediated rpoS activation mainly results from the destabilization of DsrA in the absence of Hfq, and that DsrA itself contributes to the translational activation and stability of the rpoS mRNA in an Hfq-independent manner.
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Affiliation(s)
- Wonkyong Kim
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141,
Korea
| | - Jee Soo Choi
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141,
Korea
| | - Daun Kim
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141,
Korea
| | - Doohang Shin
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141,
Korea
| | - Shinae Suk
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141,
Korea
| | - Younghoon Lee
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141,
Korea
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6
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Pei XY, Dendooven T, Sonnleitner E, Chen S, Bläsi U, Luisi BF. Architectural principles for Hfq/Crc-mediated regulation of gene expression. eLife 2019; 8:e43158. [PMID: 30758287 PMCID: PMC6422490 DOI: 10.7554/elife.43158] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Accepted: 02/11/2019] [Indexed: 12/24/2022] Open
Abstract
In diverse bacterial species, the global regulator Hfq contributes to post-transcriptional networks that control expression of numerous genes. Hfq of the opportunistic pathogen Pseudomonas aeruginosa inhibits translation of target transcripts by forming a regulatory complex with the catabolite repression protein Crc. This repressive complex acts as part of an intricate mechanism of preferred nutrient utilisation. We describe high-resolution cryo-EM structures of the assembly of Hfq and Crc bound to the translation initiation site of a target mRNA. The core of the assembly is formed through interactions of two cognate RNAs, two Hfq hexamers and a Crc pair. Additional Crc protomers are recruited to the core to generate higher-order assemblies with demonstrated regulatory activity in vivo. This study reveals how Hfq cooperates with a partner protein to regulate translation, and provides a structural basis for an RNA code that guides global regulators to interact cooperatively and regulate different RNA targets.
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Affiliation(s)
- Xue Yuan Pei
- Department of BiochemistryUniversity of CambridgeCambridgeUnited Kingdom
| | - Tom Dendooven
- Department of BiochemistryUniversity of CambridgeCambridgeUnited Kingdom
| | - Elisabeth Sonnleitner
- Department of Microbiology, Immunobiology and Genetics, Max F Perutz Laboratories, Center of Molecular BiologyUniversity of Vienna, Vienna BiocenterViennaAustria
| | - Shaoxia Chen
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
| | - Udo Bläsi
- Department of Microbiology, Immunobiology and Genetics, Max F Perutz Laboratories, Center of Molecular BiologyUniversity of Vienna, Vienna BiocenterViennaAustria
| | - Ben F Luisi
- Department of BiochemistryUniversity of CambridgeCambridgeUnited Kingdom
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7
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Maier LK, Benz J, Fischer S, Alstetter M, Jaschinski K, Hilker R, Becker A, Allers T, Soppa J, Marchfelder A. Deletion of the Sm1 encoding motif in the lsm gene results in distinct changes in the transcriptome and enhanced swarming activity of Haloferax cells. Biochimie 2015; 117:129-37. [DOI: 10.1016/j.biochi.2015.02.023] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Accepted: 02/26/2015] [Indexed: 01/08/2023]
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8
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Chattopadhyay MK, Keembiyehetty CN, Chen W, Tabor H. Polyamines Stimulate the Level of the σ38 Subunit (RpoS) of Escherichia coli RNA Polymerase, Resulting in the Induction of the Glutamate Decarboxylase-dependent Acid Response System via the gadE Regulon. J Biol Chem 2015; 290:17809-17821. [PMID: 26025365 DOI: 10.1074/jbc.m115.655688] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Indexed: 02/02/2023] Open
Abstract
To study the physiological roles of polyamines, we carried out a global microarray analysis on the effect of adding polyamines to an Escherichia coli mutant that lacks polyamines because of deletions in the genes in the polyamine biosynthetic pathway. Previously, we have reported that the earliest response to polyamine addition is the increased expression of the genes for the glutamate-dependent acid resistance system (GDAR). We also presented preliminary evidence for the involvement of rpoS and gadE regulators. In the current study, further confirmation of the regulatory roles of rpoS and gadE is shown by a comparison of genome-wide expression profiling data from a series of microarrays comparing the genes induced by polyamine addition to polyamine-free rpoS(+)/gadE(+) cells with genes induced by polyamine addition to polyamine-free ΔrpoS/gadE(+) and rpoS(+)/ΔgadE cells. The results indicate that most of the genes in the E. coli GDAR system that are induced by polyamines require rpoS and gadE. Our data also show that gadE is the main regulator of GDAR and other acid fitness island genes. Both polyamines and rpoS are necessary for the expression of gadE gene from the three promoters of gadE (P1, P2, and P3). The most important effect of polyamine addition is the very rapid increase in the level of RpoS sigma factor. Our current hypothesis is that polyamines increase the level of RpoS protein and that this increased RpoS level is responsible for the stimulation of gadE expression, which in turn induces the GDAR system in E. coli.
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Affiliation(s)
- Manas K Chattopadhyay
- Laboratory of Biochemistry and Genetics, NIDDK, National Institutes of Health, Bethesda, Maryland 20892.
| | | | - Weiping Chen
- Genomic Core Facility, NIDDK, National Institutes of Health, Bethesda, Maryland 20892
| | - Herbert Tabor
- Laboratory of Biochemistry and Genetics, NIDDK, National Institutes of Health, Bethesda, Maryland 20892
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9
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Obregon KA, Hoch CT, Sukhodolets MV. Sm-like protein Hfq: Composition of the native complex, modifications, and interactions. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2015; 1854:950-66. [PMID: 25896386 DOI: 10.1016/j.bbapap.2015.03.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Revised: 12/25/2014] [Accepted: 03/02/2015] [Indexed: 01/15/2023]
Abstract
The bacterial Sm-like protein Hfq has been linked functionally to reactions that involve RNA; however, its explicit role and primary cellular localization remain elusive. We carried out a detailed biochemical characterization of native Escherichia coli Hfq obtained through methods that preserve its posttranslational modifications. ESI-MS analyses indicate modifications in 2-3 subunits/hexamer with a molecular mass matching that of an oxidized C:18 lipid. We show that the majority of cellular Hfq cannot be extracted without detergents and that purified Hfq can be retained on hydrophobic matrices. Analyses of purified Hfq and the native Hfq complexes observed in whole-cell E. coli extracts indicate the existence of dodecameric assemblies likely stabilized by interlocking C-terminal polypeptides originating from separate Hfq hexamers and/or accessory nucleic acid. We demonstrate that cellular Hfq is redistributed between transcription complexes and an insoluble fraction that includes protein complexes harboring polynucleotide phosphorylase (PNP). This distribution pattern is consistent with a function at the interface of the apparatuses responsible for synthesis and degradation of RNA. Taken together with the results of prior studies, these results suggest that Hfq could function as an anchor/coupling factor responsible for de-solubilization of RNA and its tethering to the degradosome complex.
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Affiliation(s)
- Karla A Obregon
- Department of Chemistry and Biochemistry, Lamar University, Beaumont, TX 77710, USA
| | - Connor T Hoch
- Department of Chemistry and Biochemistry, Lamar University, Beaumont, TX 77710, USA
| | - Maxim V Sukhodolets
- Department of Chemistry and Biochemistry, Lamar University, Beaumont, TX 77710, USA.
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10
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11
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Hämmerle H, Večerek B, Resch A, Bläsi U. Duplex formation between the sRNA DsrA and rpoS mRNA is not sufficient for efficient RpoS synthesis at low temperature. RNA Biol 2013; 10:1834-41. [PMID: 24448230 DOI: 10.4161/rna.27100] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
At low temperatures the Escherichia coli rpoS mRNA, encoding the stationary phase sigma factor RpoS, forms an intramolecular secondary structure (iss) that impedes translation initiation. Under these conditions the small RNA DsrA, which is stabilzed by Hfq, forms a duplex with rpoS mRNA sequences opposite of the ribosome-binding site (rbs). Both the DEAD box helicase CsdA and Hfq have been implicated in DsrA·rpoS duplex formation. Hfq binding to A-rich sequences in the rpoS leader has been suggested to restructure the mRNA, and thereby to accelerate DsrA·rpoS duplex formation, which, in turn, was deemed to free the rpoS rbs and to permit ribosome loading on the mRNA. Several experiments designed to elucidate the role of Hfq in DsrA-mediated translational activation of rpoS mRNA have been conducted in vitro. Here, we assessed RpoS synthesis in vivo to further study the role of Hfq in rpoS regulation. We show that RpoS synthesis was reduced when DsrA was ectopically overexpressed at 24 °C in the absence of Hfq despite of DsrA·rpoS duplex formation. This observation indicated that DsrA·rpoS annealing may not be sufficient for efficient ribosome loading on rpoS mRNA. In addition, a HfqG29A mutant protein was employed, which is deficient in binding to A-rich sequences present in the rpoS leader but proficient in DsrA binding. We show that DsrA·rpoS duplex formation occurs in the presence of the HfqG29A mutant protein at low temperature, whereas synthesis of RpoS was greatly diminished. RNase T1 footprinting studies of DsrA·rpoS duplexes in the absence and presence of Hfq or HfqG29A indicated that Hfq is required to resolve a stem-loop structure in the immediate coding region of rpoS mRNA. These in vivo studies corroborate the importance of the A-rich sequences in the rpoS leader and strongly suggest that Hfq, besides stabilizing DsrA and accelerating DsrA·rpoS duplex formation, is also required to convert the rpoS mRNA into a translationally competent form.
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Affiliation(s)
- Hermann Hämmerle
- Department of Microbiology, Immunobiology and Genetics, Max F. Perutz Laboratories, Centre of Molecular Biology, University of Vienna, A-1030 Vienna, Austria
| | - Branislav Večerek
- Department of Microbiology, Immunobiology and Genetics, Max F. Perutz Laboratories, Centre of Molecular Biology, University of Vienna, A-1030 Vienna, Austria; Institute of Microbiology, Academy of Sciences of the Czech Republic, Vídeňská 1083, Prague 4-Krč, Czech Republic
| | - Armin Resch
- Department of Microbiology, Immunobiology and Genetics, Max F. Perutz Laboratories, Centre of Molecular Biology, University of Vienna, A-1030 Vienna, Austria
| | - Udo Bläsi
- Department of Microbiology, Immunobiology and Genetics, Max F. Perutz Laboratories, Centre of Molecular Biology, University of Vienna, A-1030 Vienna, Austria
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12
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Chattopadhyay MK, Tabor H. Polyamines are critical for the induction of the glutamate decarboxylase-dependent acid resistance system in Escherichia coli. J Biol Chem 2013; 288:33559-33570. [PMID: 24097985 DOI: 10.1074/jbc.m113.510552] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
As part of our studies on the biological functions of polyamines, we have used a mutant of Escherichia coli that lacks all the genes for polyamine biosynthesis for a global transcriptional analysis on the effect of added polyamines. The most striking early response to the polyamine addition is the increased expression of the genes for the glutamate-dependent acid resistance system (GDAR) that is important for the survival of the bacteria when passing through the acid environment of the stomach. Not only were the two genes for glutamate decarboxylases (gadA and gadB) and the gene for glutamate-γ-aminobutyrate antiporter (gadC) induced by the polyamine addition, but the various genes involved in the regulation of this system were also induced. We confirmed the importance of polyamines for the induction of the GDAR system by direct measurement of glutamate decarboxylase activity and acid survival. The effect of deletions of the regulatory genes on the GDAR system and the effects of overproduction of two of these genes were also studied. Strikingly, overproduction of the alternative σ factor rpoS and of the regulatory gene gadE resulted in very high levels of glutamate decarboxylase and almost complete protection against acid stress even in the absence of any polyamines. Thus, these data show that a major function of polyamines in E. coli is protection against acid stress by increasing the synthesis of glutamate decarboxylase, presumably by increasing the levels of the rpoS and gadE regulators.
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Affiliation(s)
- Manas K Chattopadhyay
- Laboratory of Biochemistry and Genetics, NIDDK, National Institutes of Health, Bethesda, Maryland 20892.
| | - Herbert Tabor
- Laboratory of Biochemistry and Genetics, NIDDK, National Institutes of Health, Bethesda, Maryland 20892
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13
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Jin Y, Wu J, Li Y, Cai Z, Huang JD. Modification of the RpoS network with a synthetic small RNA. Nucleic Acids Res 2013; 41:8332-40. [PMID: 23842672 PMCID: PMC3783183 DOI: 10.1093/nar/gkt604] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Translation of the sigma factor RpoS is activated by DsrA, RprA and ArcA, three small non-coding sRNAs (sRNA) that expose the ribosome-binding site (RBS) by opening up an inhibitory loop. In the RpoS network, no sRNAs have been found to pair with the RBS, a most common sRNA target site in bacteria. Here, we generate Ribo-0, an artificial sRNA, which represses rpoS translation by pairing with the RBS. Ribo-0 bypasses the RNA chaperon Hfq but requires the RBS to be loosely blocked. Ribo-0 interacts with DsrA and reshapes the RpoS network. Specifically, in the intact RpoS network, DsrA activates rpoS translation by freeing up the RBS. In the modified RpoS network where Ribo-0 is introduced, the DsrA-caused RBS exposure facilitates Ribo-0 binding, thereby strengthening Ribo-0 inhibition. In other words, Ribo-0 changes DsrA from an activator to an accomplice for repressing rpoS translation. This work presents an artificial mechanism of rpoS regulation, reveals mutual effects of native and synthetic players and demonstrates genetic context-dependency of their functions.
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Affiliation(s)
- Ye Jin
- Department of Biochemistry, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pok Fu Lam, Hong Kong SAR, People's Republic of China, GIAT-HKU joint Center for Synthetic Biology Engineering Research, Guangzhou Institute of Advanced Technology, Chinese Academy of Sciences, Haibin Road 1121, Nansha district, Guangzhou, Guangdong province, People's Republic of China, Guangdong and Shenzhen Key Laboratory of Male Reproductive Medicine and Genetics, Institute of Urology, Peking University Shenzhen Hospital, Shenzhen PKU-HKUST Medical Center, Shenzhen, China and Shenzhen Second People's Hospital, the First Affiliated Hospital of Shenzhen University, Shenzhen, Guangdong 518035, China
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14
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Rochat T, Bouloc P, Repoila F. Gene expression control by selective RNA processing and stabilization in bacteria. FEMS Microbiol Lett 2013; 344:104-13. [PMID: 23617839 DOI: 10.1111/1574-6968.12162] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Accepted: 04/22/2013] [Indexed: 11/27/2022] Open
Abstract
RNA maturation is a key event regulating genes at post-transcriptional level. In bacteria, it is employed to adjust the amounts of proteins and functional RNAs, often in response to environmental constraints. During the process of RNA maturation, enzymes and factors that would otherwise promote RNA degradation convert a labile RNA into a stable and biologically functional molecule.
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Affiliation(s)
- Tatiana Rochat
- INRA, UR892, Virologie et Immunologie Moléculaires, Jouy-en-Josas, France
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15
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ncRNAs and thermoregulation: a view in prokaryotes and eukaryotes. FEBS Lett 2012; 586:4061-9. [PMID: 23098758 DOI: 10.1016/j.febslet.2012.10.018] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Revised: 10/09/2012] [Accepted: 10/10/2012] [Indexed: 11/24/2022]
Abstract
During cellular stress response, a widespread inhibition of transcription and blockade of splicing and other post-transcriptional processing is detected, while certain specific genes are induced. In particular, free-living cells constantly monitor temperature. When the thermal condition changes, they activate a set of genes coding for proteins that participate in the response. Non-coding RNAs, ncRNAs, and conformational changes in specific regions of mRNAs seem also to be crucial regulators that enable the cell to adjust its physiology to environmental changes. They exert their effects following the same principles in all organisms and may affect all steps of gene expression. These ncRNAs and structural elements as related to thermal stress response in bacteria are reviewed. The resemblances to eukaryotic ncRNAs are highlighted.
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16
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Multiple activities of RNA-binding proteins S1 and Hfq. Biochimie 2012; 94:1544-53. [DOI: 10.1016/j.biochi.2012.02.010] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2011] [Accepted: 02/10/2012] [Indexed: 01/16/2023]
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17
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Murina VN, Nikulin AD. RNA-binding Sm-like proteins of bacteria and archaea. similarity and difference in structure and function. BIOCHEMISTRY (MOSCOW) 2012; 76:1434-49. [PMID: 22339597 DOI: 10.1134/s0006297911130050] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
RNA-binding proteins play a significant role in many processes of RNA metabolism, such as splicing and processing, regulation of DNA transcription and RNA translation, etc. Among the great number of RNA-binding proteins, so-called RNA-chaperones occupy an individual niche; they were named for their ability to assist RNA molecules to gain their accurate native spatial structure. When binding with RNAs, they possess the capability of altering (melting) their secondary structure, thus providing a possibility for formation of necessary intramolecular contacts between individual RNA sites for proper folding. These proteins also have an additional helper function in RNA-RNA and RNA-protein interactions. Members of such class of the RNA-binding protein family are Sm and Sm-like proteins (Sm-Like, LSm). The presence of these proteins in bacteria, archaea, and eukaryotes emphasizes their biological significance. These proteins are now attractive for researchers because of their implication in many processes associated with RNAs in bacterial and archaeal cells. This review is focused on a comparison of architecture of bacterial and archaeal LSm proteins and their interaction with different RNA molecules.
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Affiliation(s)
- V N Murina
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, Moscow Region, Russia
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18
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Sobrero P, Valverde C. The bacterial protein Hfq: much more than a mere RNA-binding factor. Crit Rev Microbiol 2012; 38:276-99. [DOI: 10.3109/1040841x.2012.664540] [Citation(s) in RCA: 116] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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19
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RelA protein stimulates the activity of RyhB small RNA by acting on RNA-binding protein Hfq. Proc Natl Acad Sci U S A 2012; 109:4621-6. [PMID: 22393021 DOI: 10.1073/pnas.1113113109] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The conserved RNA-binding protein Hfq and its associated small regulatory RNAs (sRNAs) are increasingly recognized as the players of a large network of posttranscriptional control of gene expression in Gram-negative bacteria. The role of Hfq in this network is to facilitate base pairing between sRNAs and their trans-encoded target mRNAs. Although the number of known sRNA-mRNA interactions has grown steadily, cellular factors that influence Hfq, the mediator of these interactions, have remained unknown. We report that RelA, a protein long known as the central regulator of the bacterial-stringent response, acts on Hfq and thereby affects the physiological activity of RyhB sRNA as a regulator of iron homeostasis. RyhB requires RelA in vivo to arrest growth during iron depletion and to down-regulate a subset of its target mRNAs (fdoG, nuoA, and sodA), whereas the sodB and sdhC targets are barely affected by RelA. In vitro studies with recombinant proteins show that RelA enhances multimerization of Hfq monomers and stimulates Hfq binding of RyhB and other sRNAs. Hfq from polysomes extracted from wild-type cells binds RyhB in vitro, whereas Hfq from polysomes of a relA mutant strain shows no binding. We propose that, by increasing the level of the hexameric form of Hfq, RelA enables binding of RNAs whose affinity for Hfq is low. Our results suggest that, under specific conditions and/or environments, Hfq concentrations are limiting for RNA binding, which thereby provides an opportunity for cellular proteins such as RelA to impact sRNA-mediated responses by modulating the activity of Hfq.
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20
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Abstract
In their stressful natural environments, bacteria often are in stationary phase and use their limited resources for maintenance and stress survival. Underlying this activity is the general stress response, which in Escherichia coli depends on the σS (RpoS) subunit of RNA polymerase. σS is closely related to the vegetative sigma factor σ70 (RpoD), and these two sigmas recognize similar but not identical promoter sequences. During the postexponential phase and entry into stationary phase, σS is induced by a fine-tuned combination of transcriptional, translational, and proteolytic control. In addition, regulatory "short-cuts" to high cellular σS levels, which mainly rely on the rapid inhibition of σS proteolysis, are triggered by sudden starvation for various nutrients and other stressful shift conditons. σS directly or indirectly activates more than 500 genes. Additional signal input is integrated by σS cooperating with various transcription factors in complex cascades and feedforward loops. Target gene products have stress-protective functions, redirect metabolism, affect cell envelope and cell shape, are involved in biofilm formation or pathogenesis, or can increased stationary phase and stress-induced mutagenesis. This review summarizes these diverse functions and the amazingly complex regulation of σS. At the molecular level, these processes are integrated with the partitioning of global transcription space by sigma factor competition for RNA polymerase core enzyme and signaling by nucleotide second messengers that include cAMP, (p)ppGpp, and c-di-GMP. Physiologically, σS is the key player in choosing between a lifestyle associated with postexponential growth based on nutrient scavenging and motility and a lifestyle focused on maintenance, strong stress resistance, and increased adhesiveness. Finally, research with other proteobacteria is beginning to reveal how evolution has further adapted function and regulation of σS to specific environmental niches.
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21
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Abstract
Hfq is an RNA-binding protein that is common to diverse bacterial lineages and has key roles in the control of gene expression. By facilitating the pairing of small RNAs with their target mRNAs, Hfq affects the translation and turnover rates of specific transcripts and contributes to complex post-transcriptional networks. These functions of Hfq can be attributed to its ring-like oligomeric architecture, which presents two non-equivalent binding surfaces that are capable of multiple interactions with RNA molecules. Distant homologues of Hfq occur in archaea and eukaryotes, reflecting an ancient origin for the protein family and hinting at shared functions. In this Review, we describe the salient structural and functional features of Hfq and discuss possible mechanisms by which this protein can promote RNA interactions to catalyse specific and rapid regulatory responses in vivo.
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22
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Negative effect of glucose on ompA mRNA stability: a potential role of cyclic AMP in the repression of hfq in Escherichia coli. J Bacteriol 2011; 193:5833-40. [PMID: 21840983 DOI: 10.1128/jb.05359-11] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Glucose is a carbon source that is capable of modulating the level of cyclic AMP (cAMP)-regulated genes. In the present study, we found that the stability of ompA mRNA was reduced in Escherichia coli when glucose (40 mM) was present in Luria-Bertani (LB) medium. This effect was associated with a low level of cAMP induced by the glucose. The results were confirmed with an adenylyl cyclase mutant with low levels of cAMP that are not modulated by glucose. Northern blot and Western blot analyses revealed that the host factor I (Hfq) (both mRNA and protein) levels were downregulated in the presence of cAMP. Furthermore, we showed that a complex of cAMP receptor protein (CRP) and cAMP binds to a specific P3(hfq) promoter region of hfq and regulates hfq expression. The regulation of the hfq gene was confirmed in vivo using an hfq-deficient mutant transformed with an exogenous hfq gene containing the promoter. These results demonstrated that expression of hfq was repressed by the CRP-cAMP complex. The presence of glucose resulted in increased Hfq protein levels, which decreased ompA mRNA stability. An additional experiment showed that cAMP also increased the stability of fur mRNA. Taken together, these results suggested that the repression of Hfq by cAMP may contribute to the stability of other mRNA in E. coli.
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Fonseca P, Moreno R, Rojo F. Growth of Pseudomonas putida at low temperature: global transcriptomic and proteomic analyses. ENVIRONMENTAL MICROBIOLOGY REPORTS 2011; 3:329-339. [PMID: 23761279 DOI: 10.1111/j.1758-2229.2010.00229.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
In its natural habitats (soil, water and rhizosphere), Pseudomonas putida can suffer frequent and long-term changes in temperature that affect its growth and survival. Pseudomonas putida KT2440, a well-characterized model strain, grows optimally at 30°C but can proliferate at temperatures as low as 4°C. However, little information is available on the physiological changes that occur when P. putida grows at low temperatures. To investigate this area, the transcriptome and proteome profiles of cells exponentially growing in a complex medium at 10°C were compared with those of cells exponentially growing at 30°C. Low temperature modified the expression of at least 266 genes (some 5% of the genome). Many of the genes showing differential expression were involved in energy metabolism or in the transport and binding of substrates, although genes implicated in other cellular functions were also affected. Several changes seemed directed towards neutralizing problems created by low temperature, such as increased protein misfolding, the increased stability of DNA/RNA secondary structures, reduced membrane fluidity and a reduced growth rate. The present results improve our understanding of the P. putida lifestyle at low temperature, which may be relevant for its applications in bioremediation and in promotion of plant growth.
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Affiliation(s)
- Pilar Fonseca
- Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología, CSIC, Campus UAM, Cantoblanco, 28049 Madrid, Spain
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24
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Olejniczak M. Despite similar binding to the Hfq protein regulatory RNAs widely differ in their competition performance. Biochemistry 2011; 50:4427-40. [PMID: 21510661 DOI: 10.1021/bi102043f] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The binding of nine noncoding regulatory RNAs (sRNAs) to the E. coli Hfq protein was compared using a high-throughput double filter retention assay. Despite the fact that these sRNAs have different lengths, sequences and secondary structures their Hfq binding affinities were surprisingly uniform. The analysis of sRNAs binding to Hfq mutants showed that the proximal face of Hfq, known as the binding site for DsrA RNA, is a universal sRNA binding site. Moreover, all sRNAs bound Hfq with similar association rates limited only by the rate of diffusion, while the rates of dissociation, measured in the dilution experiments, were uniformly slow. Despite that, the data showed that there was a hierarchy of sRNAs in regard to their performance in competition for access to Hfq and in their ability to facilitate the dissociation of other sRNAs from Hfq. The sRNAs also differed in their salt dependence of binding to this protein. Overall, the results suggest that despite the uniform binding of different sRNAs to the same site on Hfq their exchange on this protein is dependent on the identities of the competing sRNAs.
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Affiliation(s)
- Mikołaj Olejniczak
- Institute of Bioorganic Chemistry, Polish Academy of Sciences , Noskowskiego 12/14, Poznań, Poland.
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25
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Beich-Frandsen M, Vecerek B, Konarev PV, Sjöblom B, Kloiber K, Hämmerle H, Rajkowitsch L, Miles AJ, Kontaxis G, Wallace BA, Svergun DI, Konrat R, Bläsi U, Djinovic-Carugo K. Structural insights into the dynamics and function of the C-terminus of the E. coli RNA chaperone Hfq. Nucleic Acids Res 2011; 39:4900-15. [PMID: 21330354 PMCID: PMC3113564 DOI: 10.1093/nar/gkq1346] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The hexameric Escherichia coli RNA chaperone Hfq (Hfq(Ec)) is involved in riboregulation of target mRNAs by small trans-encoded RNAs. Hfq proteins of different bacteria comprise an evolutionarily conserved core, whereas the C-terminus is variable in length. Although the structure of the conserved core has been elucidated for several Hfq proteins, no structural information has yet been obtained for the C-terminus. Using bioinformatics, nuclear magnetic resonance spectroscopy, synchrotron radiation circular dichroism (SRCD) spectroscopy and small angle X-ray scattering we provide for the first time insights into the conformation and dynamic properties of the C-terminal extension of Hfq(Ec). These studies indicate that the C-termini are flexible and extend laterally away from the hexameric core, displaying in this way features typical of intrinsically disordered proteins that facilitate intermolecular interactions. We identified a minimal, intrinsically disordered region of the C-terminus supporting the interactions with longer RNA fragments. This minimal region together with rest of the C-terminal extension provides a flexible moiety capable of tethering long and structurally diverse RNA molecules. Furthermore, SRCD spectroscopy supported the hypothesis that RNA fragments exceeding a certain length interact with the C-termini of Hfq(Ec).
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Affiliation(s)
- Mads Beich-Frandsen
- Department of Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, Campus Vienna Biocenter 5, A-1030 Vienna, Austria
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26
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Abstract
Small RNAs (sRNAs) regulate diverse pathways, including stress responses, virulence, and metabolism in Escherichia coli. At the center of this large sRNA regulatory network is the Hfq protein. Hfq mediates the binding of sRNAs to their target mRNAs; without Hfq, most sRNAs cannot efficiently regulate target mRNA expression. Here, we show in vivo that Hfq can be a limiting factor for sRNA activity and that it can be easily depleted, causing disruption of the sRNA network. Depletion of the available Hfq can occur when sRNAs and target mRNAs are transcribed at high levels without their partners, resulting in the sequestration of Hfq into sRNA-Hfq and target mRNA-Hfq complexes. This can be avoided by coordinating the transcription of sRNAs with their target mRNAs so that they are turned on and off together to maximize duplex formation and minimize Hfq sequestration. Therefore, the limited availability of Hfq results in a highly interdependent sRNA network, wherein the activity of each sRNA depends on the activity of the other sRNAs and target mRNAs in the network.
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27
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Fender A, Elf J, Hampel K, Zimmermann B, Wagner EGH. RNAs actively cycle on the Sm-like protein Hfq. Genes Dev 2010; 24:2621-6. [PMID: 21123649 DOI: 10.1101/gad.591310] [Citation(s) in RCA: 131] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Hfq, a protein required for small RNA (sRNA)-mediated regulation in bacteria, binds RNA with low-nanomolar K(d) values and long half-lives of complexes (>100 min). This cannot be reconciled with the 1- 2-min response time of regulation in vivo. We show that RNAs displace each other on Hfq on a short time scale by RNA concentration-driven (active) cycling. Already at submicromolar concentrations of competitor RNA, half-lives of RNA-Hfq complexes are ≈1 min. We propose that competitor RNA associates transiently with RNA-Hfq complexes, RNAs exchange binding sites, and one of the RNAs eventually dissociates. This solves the "strong binding-high turnover" paradox and permits efficient use of the Hfq pool.
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Affiliation(s)
- Aurélie Fender
- Department of Cell and Molecular Biology, Biomedical Center, Uppsala University, Sweden
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28
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Resch A, Većerek B, Palavra K, Bläsi U. Requirement of the CsdA DEAD-box helicase for low temperature riboregulation of rpoS mRNA. RNA Biol 2010; 7:796-802. [PMID: 21045550 DOI: 10.4161/rna.7.6.13768] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The ribosome binding site of Escherichia coli rpoS mRNA, encoding the stationary sigma-factor RpoS, is sequestered by an inhibitory stem-loop structure (iss). Translational activation of rpoS mRNA at low temperature and during exponential growth includes Hfq-facilitated duplex formation between rpoS and the small regulatory RNA DsrA as well as a concomitant re-direction of RNAse III cleavage in the 5´-untranslated region of rpoS upon DsrA·rpoS annealing. In this way, DsrA-mediated regulation does not only activate rpoS translation by disrupting the inhibitory secondary structure but also stabilizes the rpoS transcript. Although minor structural changes by Hfq have been observed in rpoS mRNA, a prevailing question concerns unfolding of the iss in rpoS at low growth temperature. Here, we have identified the DEAD-box helicase CsdA as an ancillary factor required for low temperature activation of RpoS synthesis by DsrA. The lack of RpoS synthesis observed in the csdA mutant strain at low growth temperature could be attributed to a lack of duplex formation between rpoS and DsrA, showing that at low temperature the sole action of Hfq is not sufficient to permit DsrA·rpoS annealing. An interactome study has previously indicated an association between Hfq and CsdA. However, immunological assays did not reveal a physical interaction between Hfq and CsdA. These findings add to a model, wherein Hfq binds upstream of the rpoS iss and presents DsrA in a conformation receptive to annealing. Melting of the iss by CsdA may then permit DsrA·rpoS duplex formation, and consequently rpoS translation.
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Affiliation(s)
- Armin Resch
- Department of Microbiology, University of Vienna, Vienna, Austria
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29
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Podkaminski D, Vogel J. Small RNAs promote mRNA stability to activate the synthesis of virulence factors. Mol Microbiol 2010; 78:1327-31. [PMID: 21143308 DOI: 10.1111/j.1365-2958.2010.07428.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Although most bacterial small RNAs act to repress target mRNAs, some also activate messengers. The predominant mode of activation has been seen in 'anti-antisense' regulation whereby a small RNA prevents the formation of an inhibitory 5' mRNA structure that otherwise impairs translational initiation and protein synthesis. The translational activation might also stabilize the target yet this was considered a secondary effect in the examples known thus far. Two recent papers in Molecular Microbiology investigate post-transcriptional activation of collagenase mRNA by Clostridium VR-RNA, and streptokinase mRNA by Streptococcus FasX RNA, to suggest that small RNAs exert positive regulation of virulence genes primarily at the level of mRNA stabilization.
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Affiliation(s)
- Dimitri Podkaminski
- Institute for Molecular Infection Biology, University of Würzburg, 97080 Würzburg, Germany
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30
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Madhugiri R, Basineni SR, Klug G. Turn-over of the small non-coding RNA RprA in E. coli is influenced by osmolarity. Mol Genet Genomics 2010; 284:307-18. [PMID: 20717695 DOI: 10.1007/s00438-010-0568-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2010] [Accepted: 07/27/2010] [Indexed: 11/28/2022]
Abstract
The sRNA RprA is known to activate rpoS translation in E. coli in an osmolarity-dependent manner. We asked whether RprA stability contributes to osmolarity-dependent regulation and how the RNA binding protein Hfq and the major E. coli endonucleases contribute to this turn-over. The study reveals that osmolarity-dependent turn-over of RprA indeed contributes to its osmolarity-dependent abundance. RprA is stabilized by the RNA chaperone Hfq and in absence of Hfq its turn-over is no longer osmolarity-dependent. The stability of the RprA target mRNA rpoS shows a lower extent of osmolarity dependence, which differs from the profile observed for RprA. Thus, the effect of sucrose is specific for individual RNAs. We can attribute a role of the endoribonuclease RNase E in turn-over of RprA and an indirect effect of the endoribonuclease III in vivo. In addition, RprA is stabilized by the presence of rpoS suggesting that hybrid formation with its target may protect it against ribonucleases. In vitro RprA is cleaved by the RNase E containing degradosome and by RNase III and rpoS interferes with RNase III cleavage. We also show that temperature affects the stabilities of the sRNAs binding to rpoS and of rpoS mRNA itself differentially and that higher stability of DsrA with decreasing temperature may contribute to its high abundance at lower temperatures. This study demonstrates that environmental parameters can affect the stability of sRNAs and consequently their abundance.
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Affiliation(s)
- Ramakanth Madhugiri
- Institut für Mikrobiologie und Molekularbiologie, University of Giessen, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany
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31
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Abstract
Bacterial small noncoding RNAs carry out both positive and negative regulation of gene expression by pairing with mRNAs; in Escherichia coli, this regulation often requires the RNA chaperone Hfq. Three small regulatory RNAs (sRNAs), DsrA, RprA, and ArcZ, positively regulate translation of the sigma factor RpoS, each pairing with the 5' leader to open up an inhibitory hairpin. In vitro, rpoS interaction with sRNAs depends upon an (AAN)(4) Hfq-binding site upstream of the pairing region. Here we show that both Hfq and this Hfq binding site are required for RprA or ArcZ to act in vivo and to form a stable complex with rpoS mRNA in vitro; both were partially dispensable for DsrA at 37 degrees C. ArcZ sRNA is processed from 121 nt to a stable 56 nt species that contains the pairing region; only the 56 nt ArcZ makes a strong Hfq-dependent complex with rpoS. For each of these sRNAs, the stability of the sRNA*mRNA complexes, rather than their rate of formation, best predicted in vivo activity. These studies demonstrate that binding of Hfq to the rpoS mRNA is critical for sRNA regulation under normal conditions, but if the stability of the sRNA*mRNA complex is sufficiently high, the requirement for Hfq can be bypassed.
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