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Bouillet S, Bauer TS, Gottesman S. RpoS and the bacterial general stress response. Microbiol Mol Biol Rev 2024; 88:e0015122. [PMID: 38411096 PMCID: PMC10966952 DOI: 10.1128/mmbr.00151-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/28/2024] Open
Abstract
SUMMARYThe general stress response (GSR) is a widespread strategy developed by bacteria to adapt and respond to their changing environments. The GSR is induced by one or multiple simultaneous stresses, as well as during entry into stationary phase and leads to a global response that protects cells against multiple stresses. The alternative sigma factor RpoS is the central GSR regulator in E. coli and conserved in most γ-proteobacteria. In E. coli, RpoS is induced under conditions of nutrient deprivation and other stresses, primarily via the activation of RpoS translation and inhibition of RpoS proteolysis. This review includes recent advances in our understanding of how stresses lead to RpoS induction and a summary of the recent studies attempting to define RpoS-dependent genes and pathways.
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Affiliation(s)
- Sophie Bouillet
- Laboratory of Molecular Biology, Center for Cancer Research, NCI, Bethesda, Maryland, USA
| | - Taran S. Bauer
- Laboratory of Molecular Biology, Center for Cancer Research, NCI, Bethesda, Maryland, USA
| | - Susan Gottesman
- Laboratory of Molecular Biology, Center for Cancer Research, NCI, Bethesda, Maryland, USA
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2
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Bouillet S, Hamdallah I, Majdalani N, Tripathi A, Gottesman S. A negative feedback loop is critical for recovery of RpoS after stress in Escherichia coli. PLoS Genet 2024; 20:e1011059. [PMID: 38466775 PMCID: PMC10957080 DOI: 10.1371/journal.pgen.1011059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Revised: 03/21/2024] [Accepted: 01/17/2024] [Indexed: 03/13/2024] Open
Abstract
RpoS is an alternative sigma factor needed for the induction of the general stress response in many gammaproteobacteria. Tight regulation of RpoS levels and activity is required for bacterial growth and survival under stress. In Escherichia coli, various stresses lead to higher levels of RpoS due to increased translation and decreased degradation. During non-stress conditions, RpoS is unstable, because the adaptor protein RssB delivers RpoS to the ClpXP protease. RpoS degradation is prevented during stress by the sequestration of RssB by anti-adaptors, each of which is induced in response to specific stresses. Here, we examined how the stabilization of RpoS is reversed during recovery of the cell from stress. We found that RpoS degradation quickly resumes after recovery from phosphate starvation, carbon starvation, and when transitioning from stationary phase back to exponential phase. This process is in part mediated by the anti-adaptor IraP, known to promote RpoS stabilization during phosphate starvation via the sequestration of adaptor RssB. The rapid recovery from phosphate starvation is dependent upon a feedback loop in which RpoS transcription of rssB, encoding the adaptor protein, plays a critical role. Crl, an activator of RpoS that specifically binds to and stabilizes the complex between the RNA polymerase and RpoS, is also required for the feedback loop to function efficiently, highlighting a critical role for Crl in restoring RpoS basal levels.
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Affiliation(s)
- Sophie Bouillet
- Laboratory of Molecular Biology, Center for Cancer Research, NCI, NIH, Bethesda, Maryland, United States of America
| | - Issam Hamdallah
- Laboratory of Molecular Biology, Center for Cancer Research, NCI, NIH, Bethesda, Maryland, United States of America
| | - Nadim Majdalani
- Laboratory of Molecular Biology, Center for Cancer Research, NCI, NIH, Bethesda, Maryland, United States of America
| | - Arti Tripathi
- Laboratory of Molecular Biology, Center for Cancer Research, NCI, NIH, Bethesda, Maryland, United States of America
| | - Susan Gottesman
- Laboratory of Molecular Biology, Center for Cancer Research, NCI, NIH, Bethesda, Maryland, United States of America
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3
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Jeong GJ, Khan F, Tabassum N, Kim YM. Cellular and physiological roles of sigma factors in Vibrio spp.: A comprehensive review. Int J Biol Macromol 2024; 254:127833. [PMID: 37918595 DOI: 10.1016/j.ijbiomac.2023.127833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Revised: 10/30/2023] [Accepted: 10/30/2023] [Indexed: 11/04/2023]
Abstract
Vibrio species are motile gram-negative bacteria commonly found in aquatic environments. Vibrio species include pathogenic as well as non-pathogenic strains. Pathogenic Vibrio species have been reported in invertebrates and humans, whereas non-pathogenic strains are involved in symbiotic relationships with their eukaryotic hosts. These bacteria are also able to adapt to fluctuations in temperature, salinity, and pH, in addition to oxidative stress, and osmotic pressure in aquatic ecosystems. Moreover, they have also developed protective mechanisms against the immune systems of their hosts. Vibrio species accomplish adaptation to changing environments outside or inside the host by altering their gene expression profiles. To this end, several sigma factors specifically regulate gene expression, particularly under stressful environmental conditions. Moreover, other sigma factors are associated with biofilm formation and virulence as well. This review discusses different types of sigma and anti-sigma factors of Vibrio species involved in virulence and regulation of gene expression upon changes in environmental conditions. The evolutionary relationships between sigma factors with various physiological roles in Vibrio species are also discussed extensively.
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Affiliation(s)
- Geum-Jae Jeong
- Department of Food Science and Technology, Pukyong National University, Busan 48513, Republic of Korea
| | - Fazlurrahman Khan
- Institute of Fisheries Sciences, Pukyong National University, Busan 48513, Republic of Korea; Marine Integrated Biomedical Technology Center, The National Key Research Institutes in Universities, Pukyong National University, Busan 48513, Republic of Korea; Research Center for Marine Integrated Bionics Technology, Pukyong National University, Busan 48513, Republic of Korea.
| | - Nazia Tabassum
- Marine Integrated Biomedical Technology Center, The National Key Research Institutes in Universities, Pukyong National University, Busan 48513, Republic of Korea; Research Center for Marine Integrated Bionics Technology, Pukyong National University, Busan 48513, Republic of Korea
| | - Young-Mog Kim
- Department of Food Science and Technology, Pukyong National University, Busan 48513, Republic of Korea; Marine Integrated Biomedical Technology Center, The National Key Research Institutes in Universities, Pukyong National University, Busan 48513, Republic of Korea; Research Center for Marine Integrated Bionics Technology, Pukyong National University, Busan 48513, Republic of Korea.
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Brugger C, Schwartz J, Novick S, Tong S, Hoskins JR, Majdalani N, Kim R, Filipovski M, Wickner S, Gottesman S, Griffin PR, Deaconescu AM. Structure of phosphorylated-like RssB, the adaptor delivering σ s to the ClpXP proteolytic machinery, reveals an interface switch for activation. J Biol Chem 2023; 299:105440. [PMID: 37949227 PMCID: PMC10755785 DOI: 10.1016/j.jbc.2023.105440] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Revised: 10/15/2023] [Accepted: 10/18/2023] [Indexed: 11/12/2023] Open
Abstract
In enterobacteria such as Escherichia coli, the general stress response is mediated by σs, the stationary phase dissociable promoter specificity subunit of RNA polymerase. σs is degraded by ClpXP during active growth in a process dependent on the RssB adaptor, which is thought to be stimulated by the phosphorylation of a conserved aspartate in its N-terminal receiver domain. Here we present the crystal structure of full-length RssB bound to a beryllofluoride phosphomimic. Compared to the structure of RssB bound to the IraD anti-adaptor, our new RssB structure with bound beryllofluoride reveals conformational differences and coil-to-helix transitions in the C-terminal region of the RssB receiver domain and in the interdomain segmented helical linker. These are accompanied by masking of the α4-β5-α5 (4-5-5) "signaling" face of the RssB receiver domain by its C-terminal domain. Critically, using hydrogen-deuterium exchange mass spectrometry, we identify σs-binding determinants on the 4-5-5 face, implying that this surface needs to be unmasked to effect an interdomain interface switch and enable full σs engagement and hand-off to ClpXP. In activated receiver domains, the 4-5-5 face is often the locus of intermolecular interactions, but its masking by intramolecular contacts upon phosphorylation is unusual, emphasizing that RssB is a response regulator that undergoes atypical regulation.
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Affiliation(s)
- Christiane Brugger
- Laboratories of Molecular Medicine, Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, USA
| | - Jacob Schwartz
- Laboratories of Molecular Medicine, Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, USA
| | - Scott Novick
- Department of Molecular Medicine, The Wertheim UF Scripps Institute for Biomedical Innovation and Technology, University of Florida, Jupiter, Florida, USA
| | - Song Tong
- Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Joel R Hoskins
- Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Nadim Majdalani
- Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Rebecca Kim
- Laboratories of Molecular Medicine, Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, USA
| | - Martin Filipovski
- Laboratories of Molecular Medicine, Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, USA
| | - Sue Wickner
- Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Susan Gottesman
- Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Patrick R Griffin
- Department of Molecular Medicine, The Wertheim UF Scripps Institute for Biomedical Innovation and Technology, University of Florida, Jupiter, Florida, USA
| | - Alexandra M Deaconescu
- Laboratories of Molecular Medicine, Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, USA.
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5
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Bouillet S, Hamdallah I, Majdalani N, Tripathi A, Gottesman S. A negative feedback loop is critical for recovery of RpoS after stress in Escherichia coli.. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.09.566509. [PMID: 38077006 PMCID: PMC10705548 DOI: 10.1101/2023.11.09.566509] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/22/2023]
Abstract
RpoS is an alternative sigma factor needed for the induction of the general stress response in many gammaproteobacteria. Tight regulation of RpoS levels and activity is required for bacterial growth and survival under stress. In Escherichia coli, various stresses lead to higher levels of RpoS due to increased translation and decreased degradation. During non-stress conditions, RpoS is unstable, because the adaptor protein RssB delivers RpoS to the ClpXP protease. RpoS degradation is prevented during stress by the sequestration of RssB by anti-adaptors, each of which is induced in response to specific stresses. Here, we examined how the stabilization of RpoS is reversed during recovery of the cell from stress. We found that RpoS degradation quickly resumes after recovery from phosphate starvation, carbon starvation, and when transitioning from stationary phase back to exponential phase. This process is in part mediated by the anti-adaptor IraP, known to promote RpoS stabilization during phosphate starvation via the sequestration of adaptor RssB. The rapid recovery from phosphate starvation is dependent upon a feedback loop in which RpoS transcription of rssB, encoding the adaptor protein, plays a critical role. Crl, an activator of RpoS that specifically binds to and stabilizes the complex between the RNA polymerase and RpoS, is also required for the feedback loop to function efficiently, highlighting a critical role for Crl in restoring RpoS basal levels.
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Affiliation(s)
- Sophie Bouillet
- Laboratory of Molecular Biology, Center for Cancer Research, NCI, NIH, Bethesda, Maryland
| | - Issam Hamdallah
- Laboratory of Molecular Biology, Center for Cancer Research, NCI, NIH, Bethesda, Maryland
| | - Nadim Majdalani
- Laboratory of Molecular Biology, Center for Cancer Research, NCI, NIH, Bethesda, Maryland
| | - Arti Tripathi
- Laboratory of Molecular Biology, Center for Cancer Research, NCI, NIH, Bethesda, Maryland
| | - Susan Gottesman
- Laboratory of Molecular Biology, Center for Cancer Research, NCI, NIH, Bethesda, Maryland
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6
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Valencia EY, Barros JP, Ferenci T, Spira B. A Broad Continuum of E. coli Traits in Nature Associated with the Trade-off Between Self-preservation and Nutritional Competence. MICROBIAL ECOLOGY 2022; 83:68-82. [PMID: 33846820 DOI: 10.1007/s00248-021-01751-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Accepted: 04/05/2021] [Indexed: 06/12/2023]
Abstract
A trade-off between reproduction and survival is a characteristic of many organisms. In bacteria, growth is constrained when cellular resources are channelled towards environmental stress protection. At the core of this trade-off in Escherichia coli is RpoS, a sigma factor that diverts transcriptional resources towards general stress resistance. The constancy of RpoS levels in natural isolates is unknown. A uniform RpoS content in E. coli would impart a narrow range of resistance properties to the species, whereas a diverse set of RpoS levels in nature should result in a diverse range of stress susceptibilities. We explore the diversity of trade-off settings and phenotypes by measuring the level of RpoS protein in strains of E. coli cohabiting in a natural environment. Strains from a stream polluted with domestic waste were investigated in monthly samples. Analyses included E. coli phylogroup classification, RpoS protein level, RpoS-dependent stress phenotypes and the sequencing of rpoS mutations. The most striking finding was the continuum of RpoS levels, with a 100-fold range of RpoS amounts consistently found in individuals in the stream. Approximately 1.8% of the sampled strains carried null or non-synonymous mutations in rpoS. The natural isolates also exhibited a broad (>100-fold) range of stress resistance responses. Our results are consistent with the view that a multiplicity of survival-multiplication trade-off settings is a feature of the species E. coli. The phenotypic diversity resulting from the trade-off permits bet-hedging and the adaptation of E. coli strains to a very broad range of environments.
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Affiliation(s)
- Estela Ynes Valencia
- Departamento de Microbiologia, Instituto de Ciências Biomédicas Universidade de São Paulo, São Paulo, SP, Brazil
| | - Jackeline Pinheiro Barros
- Departamento de Microbiologia, Instituto de Ciências Biomédicas Universidade de São Paulo, São Paulo, SP, Brazil
| | - Thomas Ferenci
- School of Life and Environmental Sciences, University of Sydney, 6/403 Pacific Highway, Sydney, New South Wales, 2070, Australia
| | - Beny Spira
- Departamento de Microbiologia, Instituto de Ciências Biomédicas Universidade de São Paulo, São Paulo, SP, Brazil.
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7
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Schwartz J, Son J, Brugger C, Deaconescu AM. Phospho-dependent signaling during the general stress response by the atypical response regulator and ClpXP adaptor RssB. Protein Sci 2021; 30:899-907. [PMID: 33599047 DOI: 10.1002/pro.4047] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2021] [Revised: 02/12/2021] [Accepted: 02/12/2021] [Indexed: 11/05/2022]
Abstract
In the model organism Escherichia coli and related species, the general stress response relies on tight regulation of the intracellular levels of the promoter specificity subunit RpoS. RpoS turnover is exclusively dependent on RssB, a two-domain response regulator that functions as an adaptor that delivers RpoS to ClpXP for proteolysis. Here, we report crystal structures of the receiver domain of RssB both in its unphosphorylated form and bound to the phosphomimic BeF3 - . Surprisingly, we find only modest differences between these two structures, suggesting that truncating RssB may partially activate the receiver domain to a "meta-active" state. Our structural and sequence analysis points to RssB proteins not conforming to either the Y-T coupling scheme for signaling seen in prototypical response regulators, such as CheY, or to the signaling model of the less understood FATGUY proteins.
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Affiliation(s)
- Jacob Schwartz
- Department of Molecular Biology, Cell Biology and Biochemistry, Laboratories of Molecular Medicine Brown University, Providence, Rhode Island, USA
| | - Jonghyeon Son
- Department of Molecular Biology, Cell Biology and Biochemistry, Laboratories of Molecular Medicine Brown University, Providence, Rhode Island, USA
| | - Christiane Brugger
- Department of Molecular Biology, Cell Biology and Biochemistry, Laboratories of Molecular Medicine Brown University, Providence, Rhode Island, USA
| | - Alexandra M Deaconescu
- Department of Molecular Biology, Cell Biology and Biochemistry, Laboratories of Molecular Medicine Brown University, Providence, Rhode Island, USA
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8
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Wang Z, Zhao S, Li Y, Zhang K, Mo F, Zhang J, Hou Y, He L, Liu Z, Wang Y, Xu Y, Wang H, Buck M, Matthews SJ, Liu B. RssB-mediated σ S Activation is Regulated by a Two-Tier Mechanism via Phosphorylation and Adaptor Protein - IraD. J Mol Biol 2021; 433:166757. [PMID: 33346011 DOI: 10.1016/j.jmb.2020.166757] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2020] [Revised: 12/03/2020] [Accepted: 12/07/2020] [Indexed: 11/15/2022]
Abstract
Regulation of bacterial stress responding σS is a sophisticated process and mediated by multiple interacting partners. Controlled proteolysis of σS is regulated by RssB which maintains minimal level of σS during exponential growth but then elevates σS level while facing stresses. Bacteria developed different strategies to regulate activity of RssB, including phosphorylation of itself and production of anti-adaptors. However, the function of phosphorylation is controversial and the mechanism of anti-adaptors preventing RssB-σS interaction remains elusive. Here, we demonstrated the impact of phosphorylation on the activity of RssB and built the RssB-σS complex model. Importantly, we showed that the phosphorylation site - D58 is at the interface of RssB-σS complex. Hence, mutation or phosphorylation of D58 would weaken the interaction of RssB with σS. We found that the anti-adaptor protein IraD has higher affinity than σS to RssB and its binding interface on RssB overlaps with that for σS. And IraD-RssB complex is preferred over RssB-σS in solution, regardless of the phosphorylation state of RssB. Our study suggests that RssB possesses a two-tier mechanism for regulating σS. First, phosphorylation of RssB provides a moderate and reversible tempering of its activity, followed by a specific and robust inhibition via the anti-adaptor interaction.
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Affiliation(s)
- Zhihao Wang
- BioBank, The First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi 710061, China; Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, SW7 2AZ London, United Kingdom
| | - Siyu Zhao
- BioBank, The First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi 710061, China
| | - Yanqing Li
- BioBank, The First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi 710061, China
| | - Kaining Zhang
- BioBank, The First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi 710061, China
| | - Fei Mo
- School of Pharmacy, Xi'an Jiaotong University, Xi'an 710061, China
| | - Jiye Zhang
- School of Pharmacy, Xi'an Jiaotong University, Xi'an 710061, China
| | - Yajing Hou
- School of Pharmacy, Xi'an Jiaotong University, Xi'an 710061, China
| | - Langchong He
- School of Pharmacy, Xi'an Jiaotong University, Xi'an 710061, China
| | - Zhijun Liu
- National Facility for Protein Science, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210, China
| | - Yawen Wang
- BioBank, The First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi 710061, China
| | - Yingqi Xu
- Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, SW7 2AZ London, United Kingdom
| | - Hongliang Wang
- School of Pharmacy, Xi'an Jiaotong University, Xi'an 710061, China
| | - Martin Buck
- Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, SW7 2AZ London, United Kingdom
| | - Steve J Matthews
- Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, SW7 2AZ London, United Kingdom
| | - Bing Liu
- BioBank, The First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi 710061, China; Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, SW7 2AZ London, United Kingdom; Instrument Analysis Center of Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China.
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Micevski D, Zeth K, Mulhern TD, Schuenemann VJ, Zammit JE, Truscott KN, Dougan DA. Insight into the RssB-Mediated Recognition and Delivery of σ s to the AAA+ Protease, ClpXP. Biomolecules 2020; 10:E615. [PMID: 32316259 PMCID: PMC7226468 DOI: 10.3390/biom10040615] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 03/18/2020] [Accepted: 04/11/2020] [Indexed: 11/23/2022] Open
Abstract
In Escherichia coli, SigmaS (σS) is the master regulator of the general stress response. The cellular levels of σS are controlled by transcription, translation and protein stability. The turnover of σS, by the AAA+ protease (ClpXP), is tightly regulated by a dedicated adaptor protein, termed RssB (Regulator of Sigma S protein B)-which is an atypical member of the response regulator (RR) family. Currently however, the molecular mechanism of σS recognition and delivery by RssB is only poorly understood. Here we describe the crystal structures of both RssB domains (RssBN and RssBC) and the SAXS analysis of full-length RssB (both free and in complex with σS). Together with our biochemical analysis we propose a model for the recognition and delivery of σS by this essential adaptor protein. Similar to most bacterial RRs, the N-terminal domain of RssB (RssBN) comprises a typical mixed (βα)5-fold. Although phosphorylation of RssBN (at Asp58) is essential for high affinity binding of σS, much of the direct binding to σS occurs via the C-terminal effector domain of RssB (RssBC). In contrast to most RRs the effector domain of RssB forms a β-sandwich fold composed of two sheets surrounded by α-helical protrusions and as such, shares structural homology with serine/threonine phosphatases that exhibit a PPM/PP2C fold. Our biochemical data demonstrate that this domain plays a key role in both substrate interaction and docking to the zinc binding domain (ZBD) of ClpX. We propose that RssB docking to the ZBD of ClpX overlaps with the docking site of another regulator of RssB, the anti-adaptor IraD. Hence, we speculate that docking to ClpX may trigger release of its substrate through activation of a "closed" state (as seen in the RssB-IraD complex), thereby coupling adaptor docking (to ClpX) with substrate release. This competitive docking to RssB would prevent futile interaction of ClpX with the IraD-RssB complex (which lacks a substrate). Finally, substrate recognition by RssB appears to be regulated by a key residue (Arg117) within the α5 helix of the N-terminal domain. Importantly, this residue is not directly involved in σS interaction, as σS binding to the R117A mutant can be restored by phosphorylation. Likewise, R117A retains the ability to interact with and activate ClpX for degradation of σS, both in the presence and absence of acetyl phosphate. Therefore, we propose that this region of RssB (the α5 helix) plays a critical role in driving interaction with σS at a distal site.
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Affiliation(s)
- Dimce Micevski
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne 3086, Victoria, Australia; (D.M.); (J.E.Z.)
| | - Kornelius Zeth
- Department of Protein Evolution, Max-Planck-Institute for Developmental Biology, D-72076 Tübingen, Germany; (K.Z.); (V.J.S.)
- Department of Science and Environment, Roskilde University, DK-4000 Roskilde, Denmark
| | - Terrence D. Mulhern
- Department of Biochemistry and Molecular Biology, The University of Melbourne, Parkville 3010, Victoria, Australia;
| | - Verena J. Schuenemann
- Department of Protein Evolution, Max-Planck-Institute for Developmental Biology, D-72076 Tübingen, Germany; (K.Z.); (V.J.S.)
| | - Jessica E. Zammit
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne 3086, Victoria, Australia; (D.M.); (J.E.Z.)
| | - Kaye N. Truscott
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne 3086, Victoria, Australia; (D.M.); (J.E.Z.)
| | - David A. Dougan
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne 3086, Victoria, Australia; (D.M.); (J.E.Z.)
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10
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Abstract
Phosphorus is required for many biological molecules and essential functions, including DNA replication, transcription of RNA, protein translation, posttranslational modifications, and numerous facets of metabolism. In order to maintain the proper level of phosphate for these processes, many bacteria adapt to changes in environmental phosphate levels. The mechanisms for sensing phosphate levels and adapting to changes have been extensively studied for multiple organisms. The phosphate response of Escherichia coli alters the expression of numerous genes, many of which are involved in the acquisition and scavenging of phosphate more efficiently. This review shares findings on the mechanisms by which E. coli cells sense and respond to changes in environmental inorganic phosphate concentrations by reviewing the genes and proteins that regulate this response. The PhoR/PhoB two-component signal transduction system is central to this process and works in association with the high-affinity phosphate transporter encoded by the pstSCAB genes and the PhoU protein. Multiple models to explain how this process is regulated are discussed.
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11
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Under Elevated c-di-GMP in Escherichia coli, YcgR Alters Flagellar Motor Bias and Speed Sequentially, with Additional Negative Control of the Flagellar Regulon via the Adaptor Protein RssB. J Bacteriol 2019; 202:JB.00578-19. [PMID: 31611290 DOI: 10.1128/jb.00578-19] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Accepted: 10/11/2019] [Indexed: 12/19/2022] Open
Abstract
In Escherichia coli and Salmonella, the c-di-GMP effector YcgR inhibits flagellar motility by interacting directly with the motor to alter both its bias and speed. Here, we demonstrate that in both of these bacteria, YcgR acts sequentially, altering motor bias first and then decreasing motor speed. We show that when c-di-GMP levels are high, deletion of ycgR restores wild-type motor behavior in E. coli, indicating that YcgR is the only motor effector in this bacterium. Yet, motility and chemotaxis in soft agar do not return to normal, suggesting that there is a second mechanism that inhibits motility under these conditions. In Salmonella, c-di-GMP-induced synthesis of extracellular cellulose has been reported to entrap flagella and to be responsible for the YcgR-independent motility defect. We found that this is not the case in E. coli Instead, we found through reversion analysis that deletion of rssB, which codes for a response regulator/adaptor protein that normally directs ClpXP protease to target σS for degradation, restored wild-type motility in the ycgR mutant. Our data suggest that high c-di-GMP levels may promote altered interactions between these proteins to downregulate flagellar gene expression.IMPORTANCE Flagellum-driven motility has been studied in E. coli and Salmonella for nearly half a century. Over 60 genes control flagellar assembly and function. The expression of these genes is regulated at multiple levels in response to a variety of environmental signals. Cues that elevate c-di-GMP levels, however, inhibit motility by direct binding of the effector YcgR to the flagellar motor. In this study conducted mainly in E. coli, we show that YcgR is the only effector of motor control and tease out the order of YcgR-mediated events. In addition, we find that the σS regulator protein RssB contributes to negative regulation of flagellar gene expression when c-di-GMP levels are elevated.
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12
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Wang Z, Zhao S, Jiang S, Wang Y, Buck M, Matthews S, Liu B. Resonance assignments of N-terminal receiver domain of sigma factor S regulator RssB from Escherichia coli. BIOMOLECULAR NMR ASSIGNMENTS 2019; 13:333-337. [PMID: 31228091 DOI: 10.1007/s12104-019-09901-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Accepted: 06/18/2019] [Indexed: 06/09/2023]
Abstract
Sigma factor S (σS) are master regulator responsible for the survival of bacteria under extreme conditions. Bacteria start specific gene expression via σS promoter recognition, activating various responses to cope with external conditions. Although this self-protection mechanism is vital for bacteria to propagate and evolve, there are many puzzling research questions to be answered. For example, while interactions between σS, transcription regulator RssB, and anti-adaptor Ira proteins are believed to be responsible for controlling the cellular level of σS, their competition mechanism among them remains elusive. Furthermore, there are still debates on the location of the interface of Ira proteins and RssB and whether phosphorylation on the receiver domain is essential for σS activation remains elusive. While there is one crystal structure for the Escherichia coli receiver domain deposited in the database, the missing regions in the structure become an obstacle for functional and interactive studies. Despite attempts, there is no structure for any protein complex in this important biological process, making it one overlooked area in bacterial transcription. Here, using solution-state NMR, our near-complete resonance assignment for the receiver domain of E. coli RssB provides a basis for future structure determination and interaction studies with its many known and putative ligands.
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Affiliation(s)
- Zhihao Wang
- BioBank, The First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi, 710061, China
- Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London, SW7 2AZ, UK
| | - Siyu Zhao
- BioBank, The First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi, 710061, China
| | - Songzi Jiang
- National Facility for Protein Science, Zhangjiang Laboratory, Chinese Academy of Sciences, Shanghai, 201210, China
| | - Yawen Wang
- BioBank, The First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi, 710061, China
| | - Martin Buck
- Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London, SW7 2AZ, UK
| | - Steve Matthews
- Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London, SW7 2AZ, UK
| | - Bing Liu
- BioBank, The First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi, 710061, China.
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13
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Gottesman S. Trouble is coming: Signaling pathways that regulate general stress responses in bacteria. J Biol Chem 2019; 294:11685-11700. [PMID: 31197038 DOI: 10.1074/jbc.rev119.005593] [Citation(s) in RCA: 142] [Impact Index Per Article: 28.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Bacteria can rapidly and reversibly respond to changing environments via complex transcriptional and post-transcriptional regulatory mechanisms. Many of these adaptations are specific, with the regulatory output tailored to the inducing signal (for instance, repairing damage to cell components or improving acquisition and use of growth-limiting nutrients). However, the general stress response, activated in bacterial cells entering stationary phase or subjected to nutrient depletion or cellular damage, is unique in that its common, broad output is induced in response to many different signals. In many different bacteria, the key regulator for the general stress response is a specialized sigma factor, the promoter specificity subunit of RNA polymerase. The availability or activity of the sigma factor is regulated by complex regulatory circuits, the majority of which are post-transcriptional. In Escherichia coli, multiple small regulatory RNAs, each made in response to a different signal, positively regulate translation of the general stress response sigma factor RpoS. Stability of RpoS is regulated by multiple anti-adaptor proteins that are also synthesized in response to different signals. In this review, the modes of signaling to and levels of regulation of the E. coli general stress response are discussed. They are also used as a basis for comparison with the general stress response in other bacteria with the aim of extracting key principles that are common among different species and highlighting important unanswered questions.
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Affiliation(s)
- Susan Gottesman
- Laboratory of Molecular Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
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14
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Moreno-Cinos C, Goossens K, Salado IG, Van Der Veken P, De Winter H, Augustyns K. ClpP Protease, a Promising Antimicrobial Target. Int J Mol Sci 2019; 20:ijms20092232. [PMID: 31067645 PMCID: PMC6540193 DOI: 10.3390/ijms20092232] [Citation(s) in RCA: 63] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Revised: 04/18/2019] [Accepted: 04/29/2019] [Indexed: 01/25/2023] Open
Abstract
The caseinolytic protease proteolytic subunit (ClpP) is a serine protease playing an important role in proteostasis of eukaryotic organelles and prokaryotic cells. Alteration of ClpP function has been proved to affect the virulence and infectivity of a number of pathogens. Increased bacterial resistance to antibiotics has become a global problem and new classes of antibiotics with novel mechanisms of action are needed. In this regard, ClpP has emerged as an attractive and potentially viable option to tackle pathogen fitness without suffering cross-resistance to established antibiotic classes and, when not an essential target, without causing an evolutionary selection pressure. This opens a greater window of opportunity for the host immune system to clear the infection by itself or by co-administration with commonly prescribed antibiotics. A comprehensive overview of the function, regulation and structure of ClpP across the different organisms is given. Discussion about mechanism of action of this protease in bacterial pathogenesis and human diseases are outlined, focusing on the compounds developed in order to target the activation or inhibition of ClpP.
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Affiliation(s)
- Carlos Moreno-Cinos
- Laboratory of Medicinal Chemistry, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp, Belgium.
| | - Kenneth Goossens
- Laboratory of Medicinal Chemistry, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp, Belgium.
| | - Irene G Salado
- Laboratory of Medicinal Chemistry, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp, Belgium.
| | - Pieter Van Der Veken
- Laboratory of Medicinal Chemistry, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp, Belgium.
| | - Hans De Winter
- Laboratory of Medicinal Chemistry, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp, Belgium.
| | - Koen Augustyns
- Laboratory of Medicinal Chemistry, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp, Belgium.
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15
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Dorich V, Brugger C, Tripathi A, Hoskins JR, Tong S, Suhanovsky MM, Sastry A, Wickner S, Gottesman S, Deaconescu AM. Structural basis for inhibition of a response regulator of σ S stability by a ClpXP antiadaptor. Genes Dev 2019; 33:718-732. [PMID: 30975721 PMCID: PMC6546054 DOI: 10.1101/gad.320168.118] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Accepted: 03/19/2019] [Indexed: 11/25/2022]
Abstract
Dorich et al. present the first crystal structure of RssB bound to an antiadaptor, the DNA damage-inducible IraD. The structural data, together with mechanistic studies, suggest that RssB plasticity is critical for regulation of σS degradation. The stationary phase promoter specificity subunit σS (RpoS) is delivered to the ClpXP machinery for degradation dependent on the adaptor RssB. This adaptor-specific degradation of σS provides a major point for regulation and transcriptional reprogramming during the general stress response. RssB is an atypical response regulator and the only known ClpXP adaptor that is inhibited by multiple but dissimilar antiadaptors (IraD, IraP, and IraM). These are induced by distinct stress signals and bind to RssB in poorly understood manners to achieve stress-specific inhibition of σS turnover. Here we present the first crystal structure of RssB bound to an antiadaptor, the DNA damage-inducible IraD. The structure reveals that RssB adopts a compact closed architecture with extensive interactions between its N-terminal and C-terminal domains. The structural data, together with mechanistic studies, suggest that RssB plasticity, conferred by an interdomain glutamate-rich flexible linker, is critical for regulation of σS degradation. Structural modulation of interdomain linkers may thus constitute a general strategy for tuning response regulators.
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Affiliation(s)
- Victoria Dorich
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island 02903, USA
| | - Christiane Brugger
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island 02903, USA
| | - Arti Tripathi
- Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA
| | - Joel R Hoskins
- Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA
| | - Song Tong
- Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA
| | - Margaret M Suhanovsky
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island 02903, USA
| | - Amita Sastry
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island 02903, USA
| | - Sue Wickner
- Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA
| | - Susan Gottesman
- Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA
| | - Alexandra M Deaconescu
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island 02903, USA
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16
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Micevski D, Zammit JE, Truscott KN, Dougan DA. Anti-adaptors use distinct modes of binding to inhibit the RssB-dependent turnover of RpoS (σ(S)) by ClpXP. Front Mol Biosci 2015; 2:15. [PMID: 25988182 PMCID: PMC4428439 DOI: 10.3389/fmolb.2015.00015] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 04/08/2015] [Indexed: 12/26/2022] Open
Abstract
In Escherichia coli, σS is the master regulator of the general stress response. The level of σS changes in response to multiple stress conditions and it is regulated at many levels including protein turnover. In the absence of stress, σS is rapidly degraded by the AAA+ protease, ClpXP in a regulated manner that depends on the adaptor protein RssB. This two-component response regulator mediates the recognition of σS and its delivery to ClpXP. The turnover of σS however, can be inhibited in a stress specific manner, by one of three anti-adaptor proteins. Each anti-adaptor binds to RssB and inhibits its activity, but how this is achieved is not fully understood at a molecular level. Here, we describe details of the interaction between each anti-adaptor and RssB that leads to the stabilization of σS. By defining the domains of RssB using partial proteolysis we demonstrate that each anti-adaptor uses a distinct mode of binding to inhibit RssB activity. IraD docks specifically to the N-terminal domain of RssB, IraP interacts primarily with the C-terminal domain, while IraM interacts with both domains. Despite these differences in binding, we propose that docking of each anti-adaptor induces a conformational change in RssB, which resembles the inactive dimer of RssB. This dimer-like state of RssB not only prevents substrate binding but also triggers substrate release from a pre-bound complex.
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Affiliation(s)
- Dimce Micevski
- Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University Melbourne, VIC, Australia
| | - Jessica E Zammit
- Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University Melbourne, VIC, Australia
| | - Kaye N Truscott
- Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University Melbourne, VIC, Australia
| | - David A Dougan
- Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University Melbourne, VIC, Australia
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17
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Battesti A, Hoskins JR, Tong S, Milanesio P, Mann JM, Kravats A, Tsegaye YM, Bougdour A, Wickner S, Gottesman S. Anti-adaptors provide multiple modes for regulation of the RssB adaptor protein. Genes Dev 2014; 27:2722-35. [PMID: 24352426 PMCID: PMC3877760 DOI: 10.1101/gad.229617.113] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
A set of small protein anti-adaptors stabilizes the E. coli stress transcription factor RpoS by inhibiting the adaptor protein. In this study, Gottesman and colleagues isolate RssB mutants resistant to anti-adaptor action. Each of the anti-adaptors is unique in its interaction with RssB and sensitivity to RssB mutants. Interestingly, mutations in the C-terminal PP2C domain activate RssB and are similar to constitutively activated mutants found in a very different bacterial PP2C protein. The results provide insight into how anti-adaptors perturb response regulator function and activation. RpoS, an RNA polymerase σ factor, controls the response of Escherichia coli and related bacteria to multiple stress responses. During nonstress conditions, RpoS is rapidly degraded by ClpXP, mediated by the adaptor protein RssB, a member of the response regulator family. In response to stress, RpoS degradation ceases. Small anti-adaptor proteins—IraP, IraM, and IraD, each made under a different stress condition—block RpoS degradation. RssB mutants resistant to either IraP or IraM were isolated and analyzed in vivo and in vitro. Each of the anti-adaptors is unique in its interaction with RssB and sensitivity to RssB mutants. One class of mutants defined an RssB N-terminal region close to the phosphorylation site and critical for interaction with IraP but unnecessary for IraM and IraD function. A second class, in the RssB C-terminal PP2C-like domain, led to activation of RssB function. These mutants allowed the response regulator to act in the absence of phosphorylation but did not abolish interaction with anti-adaptors. This class of mutants is broadly resistant to the anti-adaptors and bears similarity to constitutively activated mutants found in a very different PP2C protein. The mutants provide insight into how the anti-adaptors perturb RssB response regulator function and activation.
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Affiliation(s)
- Aurelia Battesti
- Laboratory of Molecular Biology, National Cancer Institute, Bethesda, Maryland 20892, USA
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18
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Konovalova A, Søgaard-Andersen L, Kroos L. Regulated proteolysis in bacterial development. FEMS Microbiol Rev 2013; 38:493-522. [PMID: 24354618 DOI: 10.1111/1574-6976.12050] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Revised: 09/03/2013] [Accepted: 10/14/2013] [Indexed: 11/30/2022] Open
Abstract
Bacteria use proteases to control three types of events temporally and spatially during the processes of morphological development. These events are the destruction of regulatory proteins, activation of regulatory proteins, and production of signals. While some of these events are entirely cytoplasmic, others involve intramembrane proteolysis of a substrate, transmembrane signaling, or secretion. In some cases, multiple proteolytic events are organized into pathways, for example turnover of a regulatory protein activates a protease that generates a signal. We review well-studied and emerging examples and identify recurring themes and important questions for future research. We focus primarily on paradigms learned from studies of model organisms, but we note connections to regulated proteolytic events that govern bacterial adaptation, biofilm formation and disassembly, and pathogenesis.
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Affiliation(s)
- Anna Konovalova
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
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19
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Battesti A, Gottesman S. Roles of adaptor proteins in regulation of bacterial proteolysis. Curr Opin Microbiol 2013; 16:140-7. [PMID: 23375660 DOI: 10.1016/j.mib.2013.01.002] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Revised: 12/28/2012] [Accepted: 01/04/2013] [Indexed: 12/31/2022]
Abstract
Elimination of non-functional or unwanted proteins is critical for cell growth and regulation. In bacteria, ATP-dependent proteases target cytoplasmic proteins for degradation, contributing to both protein quality control and regulation of specific proteins, thus playing roles parallel to that of the proteasome in eukaryotic cells. Adaptor proteins provide a way to modulate the substrate specificity of the proteases and allow regulated proteolysis. Advances over the past few years have provided new insight into how adaptor proteins interact with both substrates and proteases and how adaptor functions are regulated. An important advance has come with the recognition of the critical roles of anti-adaptor proteins in regulating adaptor availability.
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Affiliation(s)
- Aurelia Battesti
- Laboratory of Molecular Biology, National Cancer Institute, Bethesda, MD 20892, United States
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20
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Micevski D, Dougan DA. Proteolytic regulation of stress response pathways in Escherichia coli. Subcell Biochem 2013; 66:105-28. [PMID: 23479439 DOI: 10.1007/978-94-007-5940-4_5] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Maintaining correct cellular function is a fundamental biological process for all forms of life. A critical aspect of this process is the maintenance of protein homeostasis (proteostasis) in the cell, which is largely performed by a group of proteins, referred to as the protein quality control (PQC) network. This network of proteins, comprised of chaperones and proteases, is critical for maintaining proteostasis not only during favourable growth conditions, but also in response to stress. Indeed proteases play a crucial role in the clearance of unwanted proteins that accumulate during stress, but more importantly, in the activation of various different stress response pathways. In bacteria, the cells response to stress is usually orchestrated by a specific transcription factor (sigma factor). In Escherichia coli there are seven different sigma factors, each of which responds to a particular stress, resulting in the rapid expression of a specific set of genes. The cellular concentration of each transcription factor is tightly controlled, at the level of transcription, translation and protein stability. Here we will focus on the proteolytic regulation of two sigma factors (σ(32) and σ(S)), which control the heat and general stress response pathways, respectively. This review will also briefly discuss the role proteolytic systems play in the clearance of unwanted proteins that accumulate during stress.
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Affiliation(s)
- Dimce Micevski
- Department of Biochemistry, La Trobe Institute for Molecular Science (LIMS), La Trobe University, Melbourne, 3086, Australia
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21
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Peterson CN, Levchenko I, Rabinowitz JD, Baker TA, Silhavy TJ. RpoS proteolysis is controlled directly by ATP levels in Escherichia coli. Genes Dev 2012; 26:548-53. [PMID: 22426532 DOI: 10.1101/gad.183517.111] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The master regulator of stationary phase in Escherichia coli, RpoS, responds to carbon availability through changes in stability, but the individual steps in the pathway are unknown. Here we systematically block key steps of glycolysis and the citric acid cycle and monitor the effect on RpoS degradation in vivo. Nutrient upshifts trigger RpoS degradation independently of protein synthesis by activating metabolic pathways that generate small energy molecules. Using metabolic mutants and inhibitors, we show that ATP, but not GTP or NADH, is necessary for RpoS degradation. In vitro reconstitution assays directly demonstrate that ClpXP fails to degrade RpoS, but not other proteins, at low ATP hydrolysis rates. These data suggest that cellular ATP levels directly control RpoS stability.
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Affiliation(s)
- Celeste N Peterson
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA
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22
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Battesti A, Majdalani N, Gottesman S. The RpoS-mediated general stress response in Escherichia coli. Annu Rev Microbiol 2012; 65:189-213. [PMID: 21639793 DOI: 10.1146/annurev-micro-090110-102946] [Citation(s) in RCA: 631] [Impact Index Per Article: 52.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Under conditions of nutrient deprivation or stress, or as cells enter stationary phase, Escherichia coli and related bacteria increase the accumulation of RpoS, a specialized sigma factor. RpoS-dependent gene expression leads to general stress resistance of cells. During rapid growth, RpoS translation is inhibited and any RpoS protein that is synthesized is rapidly degraded. The complex transition from exponential growth to stationary phase has been partially dissected by analyzing the induction of RpoS after specific stress treatments. Different stress conditions lead to induction of specific sRNAs that stimulate RpoS translation or to induction of small-protein antiadaptors that stabilize the protein. Recent progress has led to a better, but still far from complete, understanding of how stresses lead to RpoS induction and what RpoS-dependent genes help the cell deal with the stress.
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Affiliation(s)
- Aurelia Battesti
- Laboratory of Molecular Biology, National Cancer Institute, Bethesda, Maryland 20892, USA.
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23
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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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24
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Hengge R. Proteolysis of σS (RpoS) and the general stress response in Escherichia coli. Res Microbiol 2009; 160:667-76. [DOI: 10.1016/j.resmic.2009.08.014] [Citation(s) in RCA: 128] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2009] [Revised: 08/28/2009] [Accepted: 08/29/2009] [Indexed: 01/01/2023]
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25
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Growth phase and (p)ppGpp control of IraD, a regulator of RpoS stability, in Escherichia coli. J Bacteriol 2009; 191:7436-46. [PMID: 19820090 DOI: 10.1128/jb.00412-09] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The antiadaptor protein IraD inhibits the proteolysis of the alternative sigma factor, RpoS, which promotes the synthesis of >100 genes during the general stress response and during stationary phase. Our previous results showed that IraD determines RpoS steady-state levels during exponential growth and mediates its stabilization after DNA damage. In this study, we show by promoter fusions that iraD was upregulated during the transition from exponential growth to stationary phase. The levels of RpoS likewise rose during this transition in a partially IraD-dependent manner. The expression of iraD was under the control of ppGpp. The expression of iraD required RelA and SpoT (p)ppGpp synthetase activities and was dramatically induced by a "stringent" allele of RNA polymerase, culminating in elevated levels of RpoS. Surprisingly, DksA, normally required for transcriptional effects of the stringent response, repressed iraD expression, suggesting that DksA can exert regulatory effects independent of and opposing those of (p)ppGpp. Northern blot analysis and 5' rapid amplification of cDNA ends revealed two transcripts for iraD in wild-type strains; the smaller was regulated positively by RelA during growth; the larger transcript was induced specifically upon transition to stationary phase and was RelA SpoT dependent. A reporter fusion to the distal promoter indicated that it accounts for growth-phase regulation and DNA damage inducibility. DNA damage inducibility occurred in strains unable to synthesize (p)ppGpp, indicating an additional mode of regulation. Our results suggest that the induction of RpoS during transition to stationary phase and by (p)ppGpp occurs at least partially through IraD.
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26
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Schmidt R, Bukau B, Mogk A. Principles of general and regulatory proteolysis by AAA+ proteases in Escherichia coli. Res Microbiol 2009; 160:629-36. [PMID: 19781640 DOI: 10.1016/j.resmic.2009.08.018] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2009] [Revised: 08/20/2009] [Accepted: 08/21/2009] [Indexed: 11/25/2022]
Abstract
General and regulated proteolysis in bacteria is crucial for cellular homeostasis and relies on high substrate specificity of the executing AAA+ proteases. Here we summarize the various strategies that tightly control substrate degradation from both sides: the generation of accessible degrons and their specific recognition by AAA+ proteases and cognate adaptor proteins.
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Affiliation(s)
- Ronny Schmidt
- Zentrum für Molekulare Biologie Heidelberg (ZMBH), DKFZ-ZMBH Alliance, Universität Heidelberg, Im Neuenheimer Feld 282, Heidelberg D-69120, Germany
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27
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The response regulator SprE (RssB) modulates polyadenylation and mRNA stability in Escherichia coli. J Bacteriol 2009; 191:6812-21. [PMID: 19767441 DOI: 10.1128/jb.00870-09] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Escherichia coli, the adaptor protein SprE (RssB) controls the stability of the alternate sigma factor RpoS (sigma(38) and sigma(S)). When nutrients are abundant, SprE binds RpoS and delivers it to ClpXP for degradation, but when carbon sources are depleted, this process is inhibited. It also has been noted that overproduction of SprE is toxic. Here we show that null mutations in pcnB, encoding poly(A) polymerase I (PAP I), and in hfq, encoding the RNA chaperone Hfq, suppress this toxicity. Since PAP I, in conjunction with Hfq, is responsible for targeting RNAs, including mRNAs, for degradation by adding poly(A) tails onto their 3' ends, these data indicate that SprE helps modulate the polyadenylation pathway in E. coli. Indeed, in exponentially growing cells, sprE deletion mutants exhibit significantly reduced levels of polyadenylation and increased stability of specific mRNAs, similar to what is observed in a PAP I-deficient strain. In stationary phase, we show that SprE changes the intracellular localization of PAP I. Taken together, we propose that SprE plays a multifunctional role in controlling the transcriptome, regulating what is made via its effects on RpoS, and modulating what is degraded via its effects on polyadenylation and turnover of specific mRNAs.
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28
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Salmonella enterica serovar typhimurium strains with regulated delayed attenuation in vivo. Infect Immun 2008; 77:1071-82. [PMID: 19103774 DOI: 10.1128/iai.00693-08] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Recombinant bacterial vaccines must be fully attenuated for animal or human hosts to avoid inducing disease symptoms while exhibiting a high degree of immunogenicity. Unfortunately, many well-studied means for attenuating Salmonella render strains more susceptible to host defense stresses encountered following oral vaccination than wild-type virulent strains and/or impair their ability to effectively colonize the gut-associated and internal lymphoid tissues. This thus impairs the ability of recombinant vaccines to serve as factories to produce recombinant antigens to induce the desired protective immunity. To address these problems, we designed strains that display features of wild-type virulent strains of Salmonella at the time of immunization to enable strains first to effectively colonize lymphoid tissues and then to exhibit a regulated delayed attenuation in vivo to preclude inducing disease symptoms. We recently described one means to achieve this based on a reversible smooth-rough synthesis of lipopolysaccharide O antigen. We report here a second means to achieve regulated delayed attenuation in vivo that is based on the substitution of a tightly regulated araC P(BAD) cassette for the promoters of the fur, crp, phoPQ, and rpoS genes such that expression of these genes is dependent on arabinose provided during growth. Thus, following colonization of lymphoid tissues, the Fur, Crp, PhoPQ, and/or RpoS proteins cease to be synthesized due to the absence of arabinose such that attenuation is gradually manifest in vivo to preclude induction of diseases symptoms. Means for achieving regulated delayed attenuation can be combined with other mutations, which together may yield safe efficacious recombinant attenuated Salmonella vaccines.
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Hengge R. The two-component network and the general stress sigma factor RpoS (sigma S) in Escherichia coli. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 631:40-53. [PMID: 18792681 DOI: 10.1007/978-0-387-78885-2_4] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The general stress sigma factor RpoS (sigma s) is induced during entry into stationary phase and in response to multiple stress conditions. RpoS is regulated at the levels of transcription, translation, proteolysis and protein activity. A key factor in RpoS control is the two-component response regulator RssB, which acts as a direct recognition and targeting factor for ClpXP-mediated RpoS proteolysis. A major, but not the only phosphodonor for RssB is the complex histidine sensor kinase ArcB. ArcB coordinates RpoS proteolysis with rpoS transcription by also phosphorylating the response regulator ArcA, which besides controlling a large regulon, also acts as a transcriptional repressor for rpoS. ArcB activity depends on the redox state of the respiratory chain, which links RpoS control to the balance between energy supply and available respiratory electron acceptor. In addition, the BarA/UvrY and Rcs phosphorelay systems can activate rpoS transcription and translation, respectively. These systems are involved in the control of motility, biofilm formation and/or virulence, suggesting that further studying a potential role of RpoS in these physiological functions may be rewarding.
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Affiliation(s)
- Regine Hengge
- Institut für Biologie-Mikrobiologie, FB Biologie, Chemie und Pharmazie, Freie, Universität Berlin, Königin-Luise-str.12-16, 14195 Berlin, Germany.
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30
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Involvement of the Pta-AckA pathway in protein folding and aggregation. Res Microbiol 2008; 160:80-4. [PMID: 19026742 DOI: 10.1016/j.resmic.2008.10.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2008] [Revised: 10/06/2008] [Accepted: 10/10/2008] [Indexed: 11/21/2022]
Abstract
Acetyl phosphate is a central metabolite involved in a broad range of versatile cellular functions. Recently it was observed that in Escherichia coli the acetyl phosphate pathway is required for efficient ATP-dependent proteolysis. Deletion of the operon coding for acetyl phosphate metabolism (DeltaackApta) results in a very low cytoplasmic level of acetyl phosphate and impaired proteolysis. Here we show that the DeltaackApta mutation affects additional components of the protein quality control system. Thus, this deletion is accompanied by a decrease in protein refolding and rescue from aggregates. These results indicate the involvement of the acetyl phosphate pathway in chaperone capabilities, in addition to their effect on proteolysis.
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31
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Heuveling J, Possling A, Hengge R. A role for Lon protease in the control of the acid resistance genes ofEscherichia coli. Mol Microbiol 2008; 69:534-47. [DOI: 10.1111/j.1365-2958.2008.06306.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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32
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Bougdour A, Cunning C, Baptiste PJ, Elliott T, Gottesman S. Multiple pathways for regulation of σS (RpoS) stability in Escherichia coli via the action of multiple anti-adaptors. Mol Microbiol 2008; 68:298-313. [DOI: 10.1111/j.1365-2958.2008.06146.x] [Citation(s) in RCA: 129] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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33
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Bougdour A, Gottesman S. ppGpp regulation of RpoS degradation via anti-adaptor protein IraP. Proc Natl Acad Sci U S A 2007; 104:12896-901. [PMID: 17640895 PMCID: PMC1937563 DOI: 10.1073/pnas.0705561104] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
IraP is a small protein that interferes with the delivery of sigma(S) (RpoS) to the ClpXP protease by blocking the action of RssB, an adaptor protein for sigma(S) degradation. IraP was previously shown to mediate stabilization of sigma(S) during phosphate starvation. Here, we show that iraP is transcribed in response to phosphate starvation; this response is mediated by ppGpp. The iraP promoter is positively regulated by ppGpp, dependent on the discriminator region of the iraP promoter. Sensing of phosphate starvation requires SpoT but not RelA. The results demonstrate a target for positive regulation by ppGpp and suggest that the cell use of ppGpp to mediate a variety of starvation responses operates in part by modulating sigma(S) levels.
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Affiliation(s)
- Alexandre Bougdour
- Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | - Susan Gottesman
- Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
- To whom correspondence should be addressed. E-mail:
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34
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Fredriksson Å, Ballesteros M, Peterson CN, Persson Ö, Silhavy TJ, Nyström T. Decline in ribosomal fidelity contributes to the accumulation and stabilization of the master stress response regulator sigmaS upon carbon starvation. Genes Dev 2007; 21:862-74. [PMID: 17403784 PMCID: PMC1838536 DOI: 10.1101/gad.409407] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The sigma(S) subunit of RNA polymerase is a master regulator of Escherichia coli that retards cellular senescence and bestows cells with general stress protective functions during growth arrest. We show that mutations and drugs triggering translational errors elevate sigma(S) levels and stability. Furthermore, mutations enhancing translational fidelity attenuate induction of the rpoS regulon and prevent stabilization of sigma(S) upon carbon starvation. Destabilization of sigma(S) by increased proofreading requires the presence of the sigma(S) recognition factor SprE (RssB) and the ClpXP protease. The data further suggest that sigma(S) becomes stabilized upon starvation as a result of ClpP sequestration and this sequestration is enhanced by oxidative modifications of aberrant proteins produced by erroneous translation. ClpP overproduction counteracted starvation-induced stabilization of sigma(S), whereas overproduction of a ClpXP substrate (ssrA-tagged GFP) stabilized sigma(S) in exponentially growing cells. We present a model for the sequence of events leading to the accumulation and activation of sigma(S) upon carbon starvation, which are linked to alterations in both ribosomal fidelity and efficiency.
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Affiliation(s)
- Åsa Fredriksson
- Department of Cell and Molecular Biology-Microbiology, Göteborg University, 405 30 Göteborg, Sweden
| | - Manuel Ballesteros
- Centro Andaluz de Biologia del Desarrollo (CABD), University “Pablo de Olavide,” Ctra Utrera km1, ES-41013 Seville, Spain
| | - Celeste N. Peterson
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Örjan Persson
- Department of Cell and Molecular Biology-Microbiology, Göteborg University, 405 30 Göteborg, Sweden
| | - Thomas J. Silhavy
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA
| | - Thomas Nyström
- Department of Cell and Molecular Biology-Microbiology, Göteborg University, 405 30 Göteborg, Sweden
- Corresponding author.E-MAIL ; FAX 46-31-7732599
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35
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Klauck E, Typas A, Hengge R. The sigmaS subunit of RNA polymerase as a signal integrator and network master regulator in the general stress response in Escherichia coli. Sci Prog 2007; 90:103-27. [PMID: 17725229 PMCID: PMC10368345 DOI: 10.3184/003685007x215922] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The sigmaS (RpoS) subunit of RNA polymerase in Escherichia coli is a key master regulator which allows this bacterial model organism and important pathogen to adapt to and survive environmentally rough times. While hardly present in rapidly growing cells, sigmaS strongly accumulates in response to many different stress conditions, partly replaces the vegetative sigma subunit in RNA polymerase and thereby reprograms this enzyme to transcribe sigmaS-dependent genes (up to 10% of the E. coli genes). In this review, we summarize the extremely complex regulation of sigmaS itself and multiple signal input at the level of this master regulator, we describe the way in which sigmaS specifically recognizes "stress" promoters despite their similarity to vegetative promoters, and, while being far from comprehensive, we give a short overview of the far-reaching physiological impact of sigmaS. With sigmaS being a central and multiple signal integrator and master regulator of hundreds of genes organized in regulatory cascades and sub-networks or regulatory modules, this system also represents a key model system for analyzing complex cellular information processing and a starting point for understanding the complete regulatory network of an entire cell.
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Affiliation(s)
| | - Athanasios Typas
- Aristotle University of Thessaloniki in Greece, Freie Universität Berlin
| | - Regine Hengge
- University of Konstanz. University of Princeton (NJ, USA)
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36
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Fredriksson A, Nyström T. Conditional and replicative senescence in Escherichia coli. Curr Opin Microbiol 2006; 9:612-8. [PMID: 17067847 DOI: 10.1016/j.mib.2006.10.010] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2006] [Accepted: 10/12/2006] [Indexed: 10/24/2022]
Abstract
Analysis of the molecular mechanisms underlying the cellular degeneration of bacteria in stationary phase (known as conditional senescence) reveals interesting similarities with the aging process of higher organisms. These similarities include the role of self-inflicted oxidative damage and the importance of protein quality control systems in retarding senescence. In addition, recent data suggests that Escherichia coli cells display signs of replicative senescence, or loss of fitness, during exponential growth and that this phenomenon targets the 'older' cells. Thus, bacterial physiology might entail both conditional and mandatory aging processes.
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Affiliation(s)
- Asa Fredriksson
- Department of Cell and Molecular Biology Microbiology, Göteborg University, Box 462, 405 30 Göteborg, Sweden
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37
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Abstract
Regulated degradation of RpoS requires RssB and ClpXP protease. Mutations in hns increase both RpoS synthesis and stability, causing a twofold increase in synthesis and almost complete stabilization of RpoS, independent of effects on synthesis and independent of phosphorylation of RssB. This suggests that H-NS regulates an RssB inhibitor or inhibitors.
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Affiliation(s)
- YanNing Zhou
- Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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38
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Mizrahi I, Biran D, Ron EZ. Requirement for the acetyl phosphate pathway in Escherichia coli ATP-dependent proteolysis. Mol Microbiol 2006; 62:201-11. [PMID: 16987178 DOI: 10.1111/j.1365-2958.2006.05360.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Protein degradation is a central component of the protein quality control system. Here we show that efficient proteolysis in Escherichia coli requires the active acetyl phosphate pathway. Deletion of this pathway, leading to depletion of acetyl phosphate, results in temperature sensitivity and reduced rate of ATP-dependent proteolysis. The effect on proteolysis is general, as can be seen from the slowing down of the degradation of unstable proteins, including puromycin-derived peptides. In addition, reduced intracellular concentrations of acetyl phosphate brings about an increase in the levels of protein aggregates, which contain a wide range of proteins, as expected if a broad spectrum of substrates are involved. Additional outcomes of acetyl phosphate deficiency are elevation in the transcript levels of heat shock genes and increased thermotolerance. In E. coli the acetyl phosphate pathway is the only source of acetyl phosphate, which is a key metabolic compound involved in major cellular processes. In this communication we present evidence for the general role of the acetyl phosphate pathway in protein degradation.
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Affiliation(s)
- Itzhak Mizrahi
- Department of Molecular Microbiology and Biotechnology, The George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv 69978, Israel
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39
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Irihimovitch V, Stern DB. The sulfur acclimation SAC3 kinase is required for chloroplast transcriptional repression under sulfur limitation in Chlamydomonas reinhardtii. Proc Natl Acad Sci U S A 2006; 103:7911-6. [PMID: 16672369 PMCID: PMC1472544 DOI: 10.1073/pnas.0511042103] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Sulfur (S) deprivation responses have been studied extensively in algae and land plants; however, little is known of the signals that link perception of S status to chloroplast gene expression. Here, we have compared the chloroplast S limitation response in WT vs. sac1 and sac3 sulfur acclimation mutants of the green alga Chlamydomonas reinhardtii. We provide evidence that in the WT, chloroplast transcriptional activity rapidly decreases after removal of S from the medium, leading to reduced transcript accumulation. This decrease correlates with reduced abundance of a sigma70-like factor, Sig1, which is most likely the unique chloroplast transcription specificity factor. We further show that reduced transcription activity and diminished Sig1 accumulation are mediated by the SAC3 gene product, a putative Snf1-type Ser/Thr kinase previously shown to have both positive and negative effects on nuclear gene expression. Inclusion of the protein kinase inhibitor 6-dimethylaminopurine during S limitation yielded a pattern of expression that was largely similar to that seen in the sac3 mutant, lending support to the hypothesis that Sac3 kinase activation leads to transcriptional repression and Sig1 proteolysis. The finding that Sac3 regulates chloroplast gene expression suggests that it has a previously unknown role in integrating the S limitation response in multiple subcellular compartments.
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Affiliation(s)
- Vered Irihimovitch
- Boyce Thompson Institute for Plant Research, Cornell University, Tower Road, Ithaca, NY 14853
| | - David B. Stern
- Boyce Thompson Institute for Plant Research, Cornell University, Tower Road, Ithaca, NY 14853
- *To whom correspondence should be addressed. E-mail:
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40
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Bougdour A, Wickner S, Gottesman S. Modulating RssB activity: IraP, a novel regulator of sigma(S) stability in Escherichia coli. Genes Dev 2006; 20:884-97. [PMID: 16600914 PMCID: PMC1472289 DOI: 10.1101/gad.1400306] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The sigma(S) subunit of Escherichia coli RNA polymerase regulates the expression of stationary phase and stress response genes. sigma(S) is highly unstable in exponentially growing cells, whereas its stability increases dramatically upon starvation or under certain stress conditions. The degradation of sigma(S) is controlled by the phosphorylatable adaptor protein RssB and the ClpXP protease. RssB specifically directs sigma(S) to ClpXP. An unanswered question is how RssB-mediated degradation of sigma(S) is blocked by conditions such as glucose or phosphate starvation. We report here the identification and characterization of a new regulator of sigma(S) stability, IraP (inhibitor of RssB activity during phosphate starvation), that stabilizes sigma(S) both in vivo and in vitro. Deletion of iraP interferes with sigma(S) stabilization during phosphate starvation, but not during carbon starvation, and has a partial effect in stationary phase and nitrogen starvation. IraP interferes with RssB-dependent degradation of sigma(S) through a direct protein-protein interaction with RssB. A point mutant of IraP was isolated and found to be defective both for inhibition of sigma(S) degradation and interaction with RssB. Our results reveal a novel mechanism of regulation of sigma(S) stability through the regulation of RssB activity and identify IraP as a member of a new class of regulators, the anti-adaptor proteins.
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Affiliation(s)
- Alexandre Bougdour
- Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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41
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Peterson CN, Mandel MJ, Silhavy TJ. Escherichia coli starvation diets: essential nutrients weigh in distinctly. J Bacteriol 2005; 187:7549-53. [PMID: 16267278 PMCID: PMC1280323 DOI: 10.1128/jb.187.22.7549-7553.2005] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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42
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Rédly GA, Poole K. FpvIR control of fpvA ferric pyoverdine receptor gene expression in Pseudomonas aeruginosa: demonstration of an interaction between FpvI and FpvR and identification of mutations in each compromising this interaction. J Bacteriol 2005; 187:5648-57. [PMID: 16077110 PMCID: PMC1196079 DOI: 10.1128/jb.187.16.5648-5657.2005] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
FpvR is a presumed cytoplasmic membrane-associated anti-sigma factor that controls the activities of extracytoplasmic function sigma factors PvdS and FpvI responsible for transcription of pyoverdine biosynthetic genes and the ferric pyoverdine receptor gene, fpvA, respectively. Using deletion analysis and an in vivo bacterial two-hybrid system, FpvR interaction with these sigma factors was confirmed and shown to involve the cytoplasmic N-terminal 67 amino acid resides of FpvR. FpvR bound specifically to a C-terminal region of FpvI corresponding to region 4 of the sigma(70) family of sigma factors. FpvR and FpvI mutant proteins compromised for this interaction were generated by random and site-directed PCR mutagenesis and invariably contained secondary structure-altering proline substitution in predicted alpha-helices within the FpvR N terminus or FpvI region 4. PvdS was shown to bind to the same N-terminal region of FpvR, and FpvR mutations compromising FpvI binding also compromised PvdS binding, although some mutations had a markedly greater impact on PvdS binding. Apparently, these two sigma factors bind to FpvR in a substantially similar but not identical fashion. Intriguingly, defects in FpvR binding correlated with a substantial drop in yields of the FpvI and to a lesser extent PvdS sigma factors, suggesting that FpvR-bound FpvI and PvdS are stable while free and active sigma factor is prone to turnover.
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Affiliation(s)
- Gyula Alan Rédly
- Department of Microbiology and Immunology, Queen's University, Kingston, Ontario, Canada K7L 3N6
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43
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Bang IS, Frye JG, McClelland M, Velayudhan J, Fang FC. Alternative sigma factor interactions inSalmonella: σEand σHpromote antioxidant defences by enhancing σSlevels. Mol Microbiol 2005; 56:811-23. [PMID: 15819634 DOI: 10.1111/j.1365-2958.2005.04580.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hierarchical interactions between alternative sigma factors control sequential gene expression in Gram-positive bacteria, whereas alternative sigma factors in Gram-negative bacteria are generally regarded to direct expression of discrete gene subsets. In Salmonella enterica serovar Typhimurium (S. Typhimurium), sigma(E) responds to extracytoplasmic stress, whereas sigma(H) responds to heat shock and sigma(S) is induced during nutrient limitation. Deficiency of sigma(E), sigma(H) or sigma(S) increases S. Typhimurium susceptibility to oxidative stress, but an analysis of double and triple mutants suggested that antioxidant actions of sigma(E) and sigma(H) might be dependent on sigma(S). Transcriptional profiling of mutant Salmonella lacking sigma(E) revealed reduced expression of genes dependent on sigma(H) and sigma(S) in addition to sigma(E). Further investigation demonstrated that sigma(E) augments sigma(S) levels during stationary phase via enhanced expression of sigma(H) and the RNA-binding protein Hfq, leading to increased expression of sigma(S)-dependent genes and enhanced resistance to oxidative stress. Maximal expression of the sigma(S)-regulated gene katE required sigma(E) in Salmonella-infected macrophages as well as stationary-phase cultures. Interactions between alternative sigma factors permit the integration of diverse stress signals to produce coordinated genetic responses.
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Affiliation(s)
- Iel-Soo Bang
- Department of Laboratory Medicine, University of Washington School of Medicine, Seattle, WA 98195, USA
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44
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Mandel MJ, Silhavy TJ. Starvation for different nutrients in Escherichia coli results in differential modulation of RpoS levels and stability. J Bacteriol 2005; 187:434-42. [PMID: 15629914 PMCID: PMC543567 DOI: 10.1128/jb.187.2.434-442.2005] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Levels of RpoS increase upon glucose starvation in Escherichia coli, which leads to the transcription of genes whose products combat a variety of stresses. RpoS stability is a key level of control in this process, as SprE (RssB)-mediated degradation is inhibited under glucose starvation. Starvation for ammonia or phosphate also results in increased stress resistance and induction of RpoS-dependent genes. However, we demonstrate that RpoS levels following ammonia starvation are only slightly increased compared to growing cells and are 10-fold below the levels observed under glucose or phosphate limitation. This difference is largely due to regulated proteolysis of RpoS, as its stability in ammonia-starved cells is intermediate between that in logarithmic-phase cells and glucose-starved cells. Use of an rpoS construct that is devoid of the gene's native transcriptional and translational control regions reveals that stability differences are sufficient to explain the different levels of RpoS observed in logarithmic phase, ammonia starvation, and glucose starvation. Under phosphate starvation, however, rpoS translation is increased. The cellular response to nutrient limitation is much more complex than previously appreciated, as there is not simply one response that is activated by starvation for any essential nutrient. Our data support the hypothesis that SprE activity is the key level at which ammonia and glucose starvation signals are transmitted to RpoS, and they suggest that carbon source and/or energy limitation are necessary for full inactivation of the SprE pathway.
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Affiliation(s)
- Mark J Mandel
- Department of Molecular Biology, 310 Lewis Thomas Laboratory, Princeton University, Princeton, NJ 08544, USA
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