1
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Ho K, Harshey RM. Clustering of rRNA operons in E. coli is disrupted by σ H. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.09.20.614170. [PMID: 39345417 PMCID: PMC11429968 DOI: 10.1101/2024.09.20.614170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 10/01/2024]
Abstract
Chromosomal organization in E. coli as examined by Hi-C methodology indicates that long-range interactions are sparse. Yet, spatial co-localization or 'clustering' of 6/7 ribosomal RNA (rrn) operons distributed over half the 4.6 Mbp genome has been captured by two other methodologies - fluorescence microscopy and Mu transposition. Our current understanding of the mechanism of clustering is limited to mapping essential cis elements. To identify trans elements, we resorted to perturbing the system by chemical and physical means and observed that heat shock disrupts clustering. Levels of σH are known to rise as a cellular response to the shock. We show that elevated expression of σH alone is sufficient to disrupt clustering, independent of heat stress. The anti-clustering activity of σH does not depend on its transcriptional activity but requires core-RNAP interaction and DNA-binding activities. This activity of σH is suppressed by ectopic expression of σD suggesting a competition for core-RNAP. A query of the other five known σ factors of E. coli found that elevated expression of FecI, the ECF σ factor that controls iron citrate transport, also perturbs clustering and is also suppressed by σD. We discuss a possible scenario for how these membrane-associated σ factors participate in clustering of distant rrn loci.
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Affiliation(s)
- Khang Ho
- Department of Molecular Biosciences and LaMontagne Center for Infectious Diseases, The University of Texas at Austin, Austin, Texas, 78712, USA
| | - Rasika M. Harshey
- Department of Molecular Biosciences and LaMontagne Center for Infectious Diseases, The University of Texas at Austin, Austin, Texas, 78712, USA
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2
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Frizzell JK, Taylor RL, Ryno LM. Constitutive Activation of RpoH and the Addition of L-arabinose Influence Antibiotic Sensitivity of PHL628 E. coli. Antibiotics (Basel) 2024; 13:143. [PMID: 38391529 PMCID: PMC10886279 DOI: 10.3390/antibiotics13020143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Revised: 01/25/2024] [Accepted: 01/30/2024] [Indexed: 02/24/2024] Open
Abstract
Antibiotics are used to combat the ever-present threat of infectious diseases, but bacteria are continually evolving an assortment of defenses that enable their survival against even the most potent treatments. While the demand for novel antibiotic agents is high, the discovery of a new agent is exceedingly rare. We chose to focus on understanding how different signal transduction pathways in the gram-negative bacterium Escherichia coli (E. coli) influence the sensitivity of the organism to antibiotics from three different classes: tetracycline, chloramphenicol, and levofloxacin. Using the PHL628 strain of E. coli, we exogenously overexpressed two transcription factors, FliA and RpoH.I54N (a constitutively active mutant), to determine their influence on the minimum inhibitory concentration (MIC) and minimum duration of killing (MDK) concentration for each of the studied antibiotics. We hypothesized that activating these pathways, which upregulate genes that respond to specific stressors, could mitigate bacterial response to antibiotic treatment. We also compared the exogenous overexpression of the constitutively active RpoH mutant to thermal heat shock that has feedback loops maintained. While FliA overexpression had no impact on MIC or antibiotic tolerance, RpoH.I54N overexpression reduced the MIC for tetracycline and chloramphenicol but had no independent impact on antibiotic tolerance. Thermal heat shock alone also did not affect MIC or antibiotic tolerance. L-arabinose, the small molecule used to induce expression in our system, unexpectedly independently increased the MICs for tetracycline (>2-fold) and levofloxacin (3-fold). Additionally, the combination of thermal heat shock and arabinose provided a synergistic, 5-fold increase in MIC for chloramphenicol. Arabinose increased the tolerance, as assessed by MDK99, for chloramphenicol (2-fold) and levofloxacin (4-fold). These experiments highlight the potential of the RpoH pathway to modulate antibiotic sensitivity and the emerging implication of arabinose in enhanced MIC and antibiotic tolerance.
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Affiliation(s)
- Jenna K Frizzell
- Department of Chemistry and Biochemistry, Oberlin College, Oberlin, OH 44074, USA
| | - Ryan L Taylor
- Department of Chemistry and Biochemistry, Oberlin College, Oberlin, OH 44074, USA
| | - Lisa M Ryno
- Department of Chemistry and Biochemistry, Oberlin College, Oberlin, OH 44074, USA
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3
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Frumkin I, Laub MT. Selection of a de novo gene that can promote survival of Escherichia coli by modulating protein homeostasis pathways. Nat Ecol Evol 2023; 7:2067-2079. [PMID: 37945946 PMCID: PMC10697842 DOI: 10.1038/s41559-023-02224-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2023] [Accepted: 09/12/2023] [Indexed: 11/12/2023]
Abstract
Cellular novelty can emerge when non-functional loci become functional genes in a process termed de novo gene birth. But how proteins with random amino acid sequences beneficially integrate into existing cellular pathways remains poorly understood. We screened ~108 genes, generated from random nucleotide sequences and devoid of homology to natural genes, for their ability to rescue growth arrest of Escherichia coli cells producing the ribonuclease toxin MazF. We identified ~2,000 genes that could promote growth, probably by reducing transcription from the promoter driving toxin expression. Additionally, one random protein, named Random antitoxin of MazF (RamF), modulated protein homeostasis by interacting with chaperones, leading to MazF proteolysis and a consequent loss of its toxicity. Finally, we demonstrate that random proteins can improve during evolution by identifying beneficial mutations that turned RamF into a more efficient inhibitor. Our work provides a mechanistic basis for how de novo gene birth can produce functional proteins that effectively benefit cells evolving under stress.
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Affiliation(s)
- Idan Frumkin
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Michael T Laub
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA.
- Howard Hughes Medical Institute, Cambridge, MA, USA.
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4
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Miwa T, Taguchi H. Escherichia coli small heat shock protein IbpA plays a role in regulating the heat shock response by controlling the translation of σ 32. Proc Natl Acad Sci U S A 2023; 120:e2304841120. [PMID: 37523569 PMCID: PMC10410725 DOI: 10.1073/pnas.2304841120] [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: 03/24/2023] [Accepted: 06/23/2023] [Indexed: 08/02/2023] Open
Abstract
Small heat shock proteins (sHsps) act as ATP-independent chaperones that prevent irreversible aggregate formation by sequestering denatured proteins. IbpA, an Escherichia coli sHsp, functions not only as a chaperone but also as a suppressor of its own expression through posttranscriptional regulation, contributing to negative feedback regulation. IbpA also regulates the expression of its paralog, IbpB, in a similar manner, but the extent to which IbpA regulates other protein expressions is unclear. We have identified that IbpA down-regulates the expression of many Hsps by repressing the translation of the heat shock transcription factor σ32. The IbpA regulation not only controls the σ32 level but also contributes to the shutoff of the heat shock response. These results revealed an unexplored role of IbpA to regulate heat shock response at a translational level, which adds an alternative layer for tightly controlled and rapid expression of σ32 on demand.
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Affiliation(s)
- Tsukumi Miwa
- Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology, Midori-ku, Yokohama226-8503, Japan
| | - Hideki Taguchi
- Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology, Midori-ku, Yokohama226-8503, Japan
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5
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Gross CA, Erickson J, Grossman AD, Guisbert E, Lim B, Siegele D, Straus D. Takashi Yura: pioneer, visionary scientist, friend. Cell Stress Chaperones 2023; 28:351-356. [PMID: 37341958 PMCID: PMC10352208 DOI: 10.1007/s12192-023-01352-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/22/2023] Open
Affiliation(s)
- Carol A. Gross
- Departments of Microbiology and Immunology, and Cell and Tissue Biology, University of California, San Francisco, San Francisco, CA 94158 USA
| | - James Erickson
- Department of Biology, Texas A&M University, 3258 TAMU, College Station, TX 77845 USA
| | - Alan D. Grossman
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA USA
| | - Eric Guisbert
- Program in Biomedical Sciences, Florida Institute of Technology, Melbourne, FL 32901 USA
| | - Bentley Lim
- Microbial Sciences Institute, Yale University, West Haven, CT 06516 USA
| | - Deborah Siegele
- Department of Biology, Texas A&M University, College Station, TX 77843 USA
| | - David Straus
- Department of Biology, Virginia Commonwealth University, Richmond, VA 23284 USA
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6
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Lu Q, Chen T, Wang J, Wang F, Ye W, Ma L, Wu S. Structural Insight into the Mechanism of σ32-Mediated Transcription Initiation of Bacterial RNA Polymerase. Biomolecules 2023; 13:biom13050738. [PMID: 37238608 DOI: 10.3390/biom13050738] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 04/20/2023] [Accepted: 04/21/2023] [Indexed: 05/28/2023] Open
Abstract
Bacterial RNA polymerases (RNAP) form distinct holoenzymes with different σ factors to initiate diverse gene expression programs. In this study, we report a cryo-EM structure at 2.49 Å of RNA polymerase transcription complex containing a temperature-sensitive bacterial σ factor, σ32 (σ32-RPo). The structure of σ32-RPo reveals key interactions essential for the assembly of E. coli σ32-RNAP holoenzyme and for promoter recognition and unwinding by σ32. Specifically, a weak interaction between σ32 and -35/-10 spacer is mediated by T128 and K130 in σ32. A histidine in σ32, rather than a tryptophan in σ70, acts as a wedge to separate the base pair at the upstream junction of the transcription bubble, highlighting the differential promoter-melting capability of different residue combinations. Structure superimposition revealed relatively different orientations between βFTH and σ4 from other σ-engaged RNAPs and biochemical data suggest that a biased σ4-βFTH configuration may be adopted to modulate binding affinity to promoter so as to orchestrate the recognition and regulation of different promoters. Collectively, these unique structural features advance our understanding of the mechanism of transcription initiation mediated by different σ factors.
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Affiliation(s)
- Qiang Lu
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources, Hubei Key Laboratory of Industrial Biotechnology, School of Life Sciences, Hubei University, Wuhan 430062, China
| | - Taiyu Chen
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources, Hubei Key Laboratory of Industrial Biotechnology, School of Life Sciences, Hubei University, Wuhan 430062, China
| | - Jiening Wang
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources, Hubei Key Laboratory of Industrial Biotechnology, School of Life Sciences, Hubei University, Wuhan 430062, China
| | - Feng Wang
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources, Hubei Key Laboratory of Industrial Biotechnology, School of Life Sciences, Hubei University, Wuhan 430062, China
| | - Wenlong Ye
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources, Hubei Key Laboratory of Industrial Biotechnology, School of Life Sciences, Hubei University, Wuhan 430062, China
| | - Lixin Ma
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources, Hubei Key Laboratory of Industrial Biotechnology, School of Life Sciences, Hubei University, Wuhan 430062, China
| | - Shan Wu
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources, Hubei Key Laboratory of Industrial Biotechnology, School of Life Sciences, Hubei University, Wuhan 430062, China
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7
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Xu W, Gao W, Bu Q, Li Y. Degradation Mechanism of AAA+ Proteases and Regulation of Streptomyces Metabolism. Biomolecules 2022; 12:biom12121848. [PMID: 36551276 PMCID: PMC9775585 DOI: 10.3390/biom12121848] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Revised: 12/02/2022] [Accepted: 12/08/2022] [Indexed: 12/14/2022] Open
Abstract
Hundreds of proteins work together in microorganisms to coordinate and control normal activity in cells. Their degradation is not only the last step in the cell's lifespan but also the starting point for its recycling. In recent years, protein degradation has been extensively studied in both eukaryotic and prokaryotic organisms. Understanding the degradation process is essential for revealing the complex regulatory network in microorganisms, as well as further artificial reconstructions and applications. This review will discuss several studies on protein quality-control family members Lon, FtsH, ClpP, the proteasome in Streptomyces, and a few classical model organisms, mainly focusing on their structure, recognition mechanisms, and metabolic influences.
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Affiliation(s)
- Weifeng Xu
- Institute of Pharmaceutical Biotechnology, Zhejiang University School of Medicine, Hangzhou 310058, China
- Zhejiang Provincial Key Laboratory for Microbial Biochemistry and Metabolic Engineering, Hangzhou 310058, China
| | - Wenli Gao
- Institute of Pharmaceutical Biotechnology, Zhejiang University School of Medicine, Hangzhou 310058, China
- Zhejiang Provincial Key Laboratory for Microbial Biochemistry and Metabolic Engineering, Hangzhou 310058, China
| | - Qingting Bu
- Institute of Pharmaceutical Biotechnology, Zhejiang University School of Medicine, Hangzhou 310058, China
- Zhejiang Provincial Key Laboratory for Microbial Biochemistry and Metabolic Engineering, Hangzhou 310058, China
| | - Yongquan Li
- Institute of Pharmaceutical Biotechnology, Zhejiang University School of Medicine, Hangzhou 310058, China
- Zhejiang Provincial Key Laboratory for Microbial Biochemistry and Metabolic Engineering, Hangzhou 310058, China
- Correspondence:
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8
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Abstract
Despite our extensive knowledge of the genetic regulation of heat shock proteins (HSPs), the evolutionary routes that allow bacteria to adaptively tune their HSP levels and corresponding proteostatic robustness have been explored less. In this report, directed evolution experiments using the Escherichia coli model system unexpectedly revealed that seemingly random single mutations in its tnaA gene can confer significant heat resistance. Closer examination, however, indicated that these mutations create folding-deficient and aggregation-prone TnaA variants that in turn can endogenously and preemptively trigger HSP expression to cause heat resistance. These findings, importantly, demonstrate that even erosive mutations with disruptive effects on protein structure and functionality can still yield true gain-of-function alleles with a selective advantage in adaptive evolution.
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9
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Yura T. Regulation of the heat shock response in Escherichia coli: history and perspectives. Genes Genet Syst 2019; 94:103-108. [DOI: 10.1266/ggs.19-00005] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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10
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Yura T, Miyazaki R, Fujiwara K, Ito K, Chiba S, Mori H, Akiyama Y. Heat shock transcription factor σ<sup>32</sup> defective in membrane transport can be suppressed by transposon insertion into genes encoding a restriction enzyme subunit or a putative autotransporter in <i>Escherichia coli</i>. Genes Genet Syst 2018; 93:229-235. [DOI: 10.1266/ggs.18-00040] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Affiliation(s)
- Takashi Yura
- Faculty of Life Sciences, Kyoto Sangyo University
| | - Ryoji Miyazaki
- Institute for Frontier Life and Medical Sciences, Kyoto University
| | | | - Koreaki Ito
- Faculty of Life Sciences, Kyoto Sangyo University
| | | | - Hiroyuki Mori
- Institute for Frontier Life and Medical Sciences, Kyoto University
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11
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Potential Applications of the Escherichia coli Heat Shock Response in Synthetic Biology. Trends Biotechnol 2018; 36:186-198. [DOI: 10.1016/j.tibtech.2017.10.014] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 10/20/2017] [Accepted: 10/20/2017] [Indexed: 01/06/2023]
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12
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Schramm FD, Heinrich K, Thüring M, Bernhardt J, Jonas K. An essential regulatory function of the DnaK chaperone dictates the decision between proliferation and maintenance in Caulobacter crescentus. PLoS Genet 2017; 13:e1007148. [PMID: 29281627 PMCID: PMC5760092 DOI: 10.1371/journal.pgen.1007148] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Revised: 01/09/2018] [Accepted: 12/11/2017] [Indexed: 11/19/2022] Open
Abstract
Hsp70 chaperones are well known for their important functions in maintaining protein homeostasis during thermal stress conditions. In many bacteria the Hsp70 homolog DnaK is also required for growth in the absence of stress. The molecular reasons underlying Hsp70 essentiality remain in most cases unclear. Here, we demonstrate that DnaK is essential in the α-proteobacterium Caulobacter crescentus due to its regulatory function in gene expression. Using a suppressor screen we identified mutations that allow growth in the absence of DnaK. All mutations reduced the activity of the heat shock sigma factor σ32, demonstrating that the DnaK-dependent inactivation of σ32 is a growth requirement. While most mutations occurred in the rpoH gene encoding σ32, we also identified mutations affecting σ32 activity or stability in trans, providing important new insight into the regulatory mechanisms controlling σ32 activity. Most notably, we describe a mutation in the ATP dependent protease HslUV that induces rapid degradation of σ32, and a mutation leading to increased levels of the house keeping σ70 that outcompete σ32 for binding to the RNA polymerase. We demonstrate that σ32 inhibits growth and that its unrestrained activity leads to an extensive reprogramming of global gene expression, resulting in upregulation of repair and maintenance functions and downregulation of the growth-promoting functions of protein translation, DNA replication and certain metabolic processes. While this re-allocation from proliferative to maintenance functions could provide an advantage during heat stress, it leads to growth defects under favorable conditions. We conclude that Caulobacter has co-opted the DnaK chaperone system as an essential regulator of gene expression under conditions when its folding activity is dispensable. Molecular chaperones of the Hsp70 family belong to the most conserved cellular machineries throughout the tree of life. These proteins play key roles in maintaining protein homeostasis, especially under heat stress conditions. In diverse bacteria the Hsp70 homolog DnaK is essential for growth even in the absence of stress. However, the molecular mechanisms underlying the essential nature of DnaK have in most cases not been studied. We found in the α-proteobacterium Caulobacter crescentus that the function of DnaK as a folding catalyst is dispensable in the absence of stress. Instead, its sole essential function under such conditions is to inhibit the activity of the heat shock sigma factor σ32. Our findings highlight that some bacteria have co-opted chaperones as essential regulators of gene expression under conditions when their folding activity is not required. Furthermore, our work illustrates that essential genes can perform different essential functions in discrete growth conditions.
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Affiliation(s)
- Frederic D. Schramm
- Science for Life Laboratory, Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
- LOEWE Center for Synthetic Microbiology (SYNMIKRO), Philipps University Marburg, Marburg, Germany
| | - Kristina Heinrich
- Science for Life Laboratory, Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
- LOEWE Center for Synthetic Microbiology (SYNMIKRO), Philipps University Marburg, Marburg, Germany
| | - Marietta Thüring
- LOEWE Center for Synthetic Microbiology (SYNMIKRO), Philipps University Marburg, Marburg, Germany
| | - Jörg Bernhardt
- Institute of Microbiology, Ernst-Moritz-Arndt University Greifswald, Greifswald, Germany
| | - Kristina Jonas
- Science for Life Laboratory, Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
- LOEWE Center for Synthetic Microbiology (SYNMIKRO), Philipps University Marburg, Marburg, Germany
- * E-mail:
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13
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Morgan GJ, Burkhardt DH, Kelly JW, Powers ET. Translation efficiency is maintained at elevated temperature in Escherichia coli. J Biol Chem 2017; 293:777-793. [PMID: 29183994 DOI: 10.1074/jbc.ra117.000284] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Revised: 11/22/2017] [Indexed: 01/30/2023] Open
Abstract
Cellular protein levels are dictated by the balance between gene transcription, mRNA translation, and protein degradation, among other factors. Translation requires the interplay of several RNA hybridization processes, which are expected to be temperature-sensitive. We used ribosome profiling to monitor translation in Escherichia coli at 30 °C and to investigate how this changes after 10-20 min of heat shock at 42 °C. Translation efficiencies are robustly maintained after thermal heat shock and after mimicking the heat-shock response transcriptional program at 30 °C by overexpressing the heat shock σ factor encoded by the rpoH gene. We compared translation efficiency, the ratio of ribosome footprint reads to mRNA reads for each gene, to parameters derived from gene sequences. Genes with stable mRNA structures, non-optimal codon use, and those whose gene product is cotranslationally translocated into the inner membrane are generally less highly translated than other genes. Comparison with other published datasets suggests a role for translational elongation in coupling mRNA structures to translation initiation. Genome-wide calculations of the temperature dependence of mRNA structure predict that relatively few mRNAs show a melting transition between 30 and 42 °C, consistent with the observed lack of changes in translation efficiency. We developed a linear model with six parameters that can predict 38% of the variation in translation efficiency between genes, which may be useful in interpreting transcriptome data.
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Affiliation(s)
- Gareth J Morgan
- From the Departments of Chemistry and Molecular Medicine and
| | - David H Burkhardt
- California Institute of Quantitative Biosciences and Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, California 94158
| | - Jeffery W Kelly
- From the Departments of Chemistry and Molecular Medicine and.,Skaggs Institute for Chemical Biology, The Scripps Research Institute, La, Jolla, California 92037, and
| | - Evan T Powers
- From the Departments of Chemistry and Molecular Medicine and
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Roncarati D, Scarlato V. Regulation of heat-shock genes in bacteria: from signal sensing to gene expression output. FEMS Microbiol Rev 2017; 41:549-574. [PMID: 28402413 DOI: 10.1093/femsre/fux015] [Citation(s) in RCA: 113] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Accepted: 03/14/2017] [Indexed: 02/07/2023] Open
Abstract
The heat-shock response is a mechanism of cellular protection against sudden adverse environmental growth conditions and results in the prompt production of various heat-shock proteins. In bacteria, specific sensory biomolecules sense temperature fluctuations and transduce intercellular signals that coordinate gene expression outputs. Sensory biomolecules, also known as thermosensors, include nucleic acids (DNA or RNA) and proteins. Once a stress signal is perceived, it is transduced to invoke specific molecular mechanisms controlling transcription of genes coding for heat-shock proteins. Transcriptional regulation of heat-shock genes can be under either positive or negative control mediated by dedicated regulatory proteins. Positive regulation exploits specific alternative sigma factors to redirect the RNA polymerase enzyme to a subset of selected promoters, while negative regulation is mediated by transcriptional repressors. Interestingly, while various bacteria adopt either exclusively positive or negative mechanisms, in some microorganisms these two opposite strategies coexist, establishing complex networks regulating heat-shock genes. Here, we comprehensively summarize molecular mechanisms that microorganisms have adopted to finely control transcription of heat-shock genes.
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Affiliation(s)
- Davide Roncarati
- Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, 40126 Bologna, Italy
| | - Vincenzo Scarlato
- Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, 40126 Bologna, Italy
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15
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Anglès F, Castanié-Cornet MP, Slama N, Dinclaux M, Cirinesi AM, Portais JC, Létisse F, Genevaux P. Multilevel interaction of the DnaK/DnaJ(HSP70/HSP40) stress-responsive chaperone machine with the central metabolism. Sci Rep 2017; 7:41341. [PMID: 28128357 PMCID: PMC5269706 DOI: 10.1038/srep41341] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Accepted: 12/16/2016] [Indexed: 12/23/2022] Open
Abstract
Networks of molecular chaperones maintain cellular protein homeostasis by acting at nearly every step in the biogenesis of proteins and protein complexes. Herein, we demonstrate that the major chaperone DnaK/HSP70 of the model bacterium Escherichia coli is critical for the proper functioning of the central metabolism and for the cellular response to carbon nutrition changes, either directly or indirectly via the control of the heat-shock response. We identified carbon sources whose utilization was positively or negatively affected by DnaK and isolated several central metabolism genes (among other genes identified in this work) that compensate for the lack of DnaK and/or DnaK/Trigger Factor chaperone functions in vivo. Using carbon sources with specific entry points coupled to NMR analyses of real-time carbon assimilation, metabolic coproducts production and flux rearrangements, we demonstrate that DnaK significantly impacts the hierarchical order of carbon sources utilization, the excretion of main coproducts and the distribution of metabolic fluxes, thus revealing a multilevel interaction of DnaK with the central metabolism.
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Affiliation(s)
- Fréderic Anglès
- Laboratoire de Microbiologie et de Génétique Moléculaires, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, 118 route de Narbonne, 31062 Toulouse Cedex 9, France.,LISBP, Université de Toulouse, CNRS, INRA, INSA F-31400 Toulouse, France
| | - Marie-Pierre Castanié-Cornet
- Laboratoire de Microbiologie et de Génétique Moléculaires, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, 118 route de Narbonne, 31062 Toulouse Cedex 9, France
| | - Nawel Slama
- Laboratoire de Microbiologie et de Génétique Moléculaires, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, 118 route de Narbonne, 31062 Toulouse Cedex 9, France
| | - Mickael Dinclaux
- LISBP, Université de Toulouse, CNRS, INRA, INSA F-31400 Toulouse, France
| | - Anne-Marie Cirinesi
- Laboratoire de Microbiologie et de Génétique Moléculaires, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, 118 route de Narbonne, 31062 Toulouse Cedex 9, France
| | | | - Fabien Létisse
- LISBP, Université de Toulouse, CNRS, INRA, INSA F-31400 Toulouse, France
| | - Pierre Genevaux
- Laboratoire de Microbiologie et de Génétique Moléculaires, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, 118 route de Narbonne, 31062 Toulouse Cedex 9, France
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16
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A Novel SRP Recognition Sequence in the Homeostatic Control Region of Heat Shock Transcription Factor σ32. Sci Rep 2016; 6:24147. [PMID: 27052372 PMCID: PMC4823717 DOI: 10.1038/srep24147] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Accepted: 03/21/2016] [Indexed: 12/29/2022] Open
Abstract
Heat shock response (HSR) generally plays a major role in sustaining protein homeostasis. In Escherichia coli, the activity and amount of the dedicated transcription factor σ32 transiently increase upon heat shock. The initial induction is followed by chaperone-mediated negative feedback to inactivate and degrade σ32. Previous work reported that signal recognition particle (SRP)-dependent targeting of σ32 to the membrane is essential for feedback control, though how SRP recognizes σ32 remained unknown. Extensive photo- and disulfide cross-linking studies in vivo now reveal that the highly conserved regulatory region of σ32 that lacks a consecutive hydrophobic stretch interacts with the signal peptide-binding site of Ffh (the protein subunit of SRP). Importantly, the σ32–Ffh interaction observed was significantly affected by mutations in this region that compromise the feedback regulation, but not by deleting the DnaK/DnaJ chaperones. Homeostatic regulation of HSR thus requires a novel type of SRP recognition mechanism.
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17
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Patra M, Roy SS, Dasgupta R, Basu T. GroEL to DnaK chaperone network behind the stability modulation of σ32at physiological temperature inEscherichia coli. FEBS Lett 2015; 589:4047-52. [DOI: 10.1016/j.febslet.2015.10.034] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Revised: 10/24/2015] [Accepted: 10/27/2015] [Indexed: 01/29/2023]
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18
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Mechanism to control the cell lysis and the cell survival strategy in stationary phase under heat stress. SPRINGERPLUS 2015; 4:599. [PMID: 26543734 PMCID: PMC4627973 DOI: 10.1186/s40064-015-1415-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2015] [Accepted: 10/07/2015] [Indexed: 11/10/2022]
Abstract
An array of stress signals triggering the bacterial cellular stress response is well known in Escherichia coli and other bacteria. Heat stress is usually sensed through the misfolded outer membrane porin (OMP) precursors in the periplasm, resulting in the activation of σ(E) (encoded by rpoE), which binds to RNA polymerase to start the transcription of genes required for responding against the heat stress signal. At the elevated temperatures, σ(E) also serves as the transcription factor for σ(H) (the main heat shock sigma factor, encoded by rpoH), which is involved in the expression of several genes whose products deal with the cytoplasmic unfolded proteins. Besides, oxidative stress in form of the reactive oxygen species (ROS) that accumulate due to heat stress, has been found to give rise to viable but non-culturable (VBNC) cells at the early stationary phase, which is in turn lysed by the σ(E)-dependent process. Such lysis of the defective cells may generate nutrients for the remaining population to survive with the capacity of formation of colony forming units (CFUs). σ(H) is also known to regulate the transcription of the major heat shock proteins (HSPs) required for heat shock response (HSR) resulting in cellular survival. Present review concentrated on the cellular survival against heat stress employing the harmonized impact of σ(E) and σ(H) regulons and the HSPs as well as their inter connectivity towards the maintenance of cellular survival.
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19
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Liu Y, Zhang X, Chen W, Tan YL, Kelly JW. Fluorescence Turn-On Folding Sensor To Monitor Proteome Stress in Live Cells. J Am Chem Soc 2015; 137:11303-11. [PMID: 26305239 PMCID: PMC4755273 DOI: 10.1021/jacs.5b04366] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Proteome misfolding and/or aggregation, caused by a thermal perturbation or a related stress, transiently challenges the cellular protein homeostasis (proteostasis) network capacity of cells by consuming chaperone/chaperonin pathway and degradation pathway capacity. Developing protein client-based probes to quantify the cellular proteostasis network capacity in real time is highly desirable. Herein we introduce a small-molecule-regulated fluorescent protein folding sensor based on a thermo-labile mutant of the de novo designed retroaldolase (RA) enzyme. Since RA enzyme activity is not present in any cell, the protein folding sensor is bioorthogonal. The fluorogenic small molecule was designed to become fluorescent when it binds to and covalently reacts with folded and functional RA. Thus, in the first experimental paradigm, cellular proteostasis network capacity and its dynamics are reflected by RA-small molecule conjugate fluorescence, which correlates with the amount of folded and functional RA present, provided that pharmacologic chaperoning is minimized. In the second experimental scenario, the RA-fluorogenic probe conjugate is pre-formed in a cell by simply adding the fluorogenic probe to the cell culture media. Unreacted probe is then washed away before a proteome misfolding stress is applied in a pulse-chase-type experiment. Insufficient proteostasis network capacity is reflected by aggregate formation of the fluorescent RA-fluorogenic probe conjugate. Removal of the stress results in apparent RA-fluorogenic probe conjugate re-folding, mediated in part by the heat-shock response transcriptional program augmenting cytosolic proteostasis network capacity, and in part by time-dependent RA-fluorogenic probe conjugate degradation by cellular proteolysis.
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Affiliation(s)
- Yu Liu
- Department of Chemistry, ‡Department of Molecular and Experimental Medicine, and §The Skaggs Institute for Chemical Biology, The Scripps Research Institute , La Jolla, California 92037, United States
| | - Xin Zhang
- Department of Chemistry, ‡Department of Molecular and Experimental Medicine, and §The Skaggs Institute for Chemical Biology, The Scripps Research Institute , La Jolla, California 92037, United States
| | - Wentao Chen
- Department of Chemistry, ‡Department of Molecular and Experimental Medicine, and §The Skaggs Institute for Chemical Biology, The Scripps Research Institute , La Jolla, California 92037, United States
| | - Yun Lei Tan
- Department of Chemistry, ‡Department of Molecular and Experimental Medicine, and §The Skaggs Institute for Chemical Biology, The Scripps Research Institute , La Jolla, California 92037, United States
| | - Jeffery W Kelly
- Department of Chemistry, ‡Department of Molecular and Experimental Medicine, and §The Skaggs Institute for Chemical Biology, The Scripps Research Institute , La Jolla, California 92037, United States
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20
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Eisenhardt BD. Small heat shock proteins: recent developments. Biomol Concepts 2015; 4:583-95. [PMID: 25436758 DOI: 10.1515/bmc-2013-0028] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Accepted: 10/07/2013] [Indexed: 12/14/2022] Open
Abstract
Small heat shock proteins (sHSPs) are abundantly present in many different organisms at elevated temperatures. Members of the subgroup of alpha crystallin domain (ACD)-type sHSPs belong to the large family of protein chaperones. They bind non-native proteins in an ATP-independent manner, thereby holding the incorporated clients soluble for subsequent refolding by other molecular chaperoning systems. sHSPs do not actively refold incorporated peptides therefore they are sometimes referred to as holdases. Varying numbers of sHSPs have been documented in the different domains of life and dependent on the analyzed organism. Generally, diverse sHSPs possess more sequence similarities in the conserved ACD, whereas the N- and C-terminal extensions are less conserved. Despite their designation as sHSPs, they are not solely present during heat stress. sHSPs presumably help to protect cells under various stresses, but they were also found during development, e.g., in embryonic development of higher plants which is associated with ongoing seed desiccation. The functional and physiological relevance of several different sHSPs in one organism remains still unclear, especially in plants where several highly similar sHSPs are present in the same compartment. The wide range of biotic and abiotic stresses that induce the expression of multiple sHSP genes makes it challenging to define the physiological relevance of each of these versatile proteins.
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21
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Individual and collective contributions of chaperoning and degradation to protein homeostasis in E. coli. Cell Rep 2015; 11:321-33. [PMID: 25843722 DOI: 10.1016/j.celrep.2015.03.018] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 01/29/2015] [Accepted: 03/07/2015] [Indexed: 11/24/2022] Open
Abstract
The folding fate of a protein in vivo is determined by the interplay between a protein's folding energy landscape and the actions of the proteostasis network, including molecular chaperones and degradation enzymes. The mechanisms of individual components of the E. coli proteostasis network have been studied extensively, but much less is known about how they function as a system. We used an integrated experimental and computational approach to quantitatively analyze the folding outcomes (native folding versus aggregation versus degradation) of three test proteins biosynthesized in E. coli under a variety of conditions. Overexpression of the entire proteostasis network benefited all three test proteins, but the effect of upregulating individual chaperones or the major degradation enzyme, Lon, varied for proteins with different biophysical properties. In sum, the impact of the E. coli proteostasis network is a consequence of concerted action by the Hsp70 system (DnaK/DnaJ/GrpE), the Hsp60 system (GroEL/GroES), and Lon.
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22
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Abstract
Microorganisms live in fluctuating environments, requiring stress response pathways to resist environmental insults and stress. These pathways dynamically monitor cellular status, and mediate adaptive changes by remodeling the proteome, largely accomplished by remodeling transcriptional networks and protein degradation. The complementarity of fast, specific proteolytic degradation and slower, broad transcriptomic changes gives cells the mechanistic repertoire to dynamically adjust cellular processes and optimize response behavior. Together, this enables cells to minimize the 'cost' of the response while maximizing the ability to survive environmental stress. Here we highlight recent progress in our understanding of transcriptional networks and proteolysis that illustrates the design principles used by bacteria to generate the complex behaviors required to resist stress.
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23
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Zhang X, Liu Y, Genereux JC, Nolan C, Singh M, Kelly JW. Heat-shock response transcriptional program enables high-yield and high-quality recombinant protein production in Escherichia coli. ACS Chem Biol 2014; 9:1945-9. [PMID: 25051296 PMCID: PMC4168666 DOI: 10.1021/cb5004477] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
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The biosynthesis of soluble, properly
folded recombinant proteins
in large quantities from Escherichia coli is desirable
for academic research and industrial protein production. The basal E. coli protein homeostasis (proteostasis) network capacity
is often insufficient to efficiently fold overexpressed proteins.
Herein we demonstrate that a transcriptionally reprogrammed E. coli proteostasis network is generally superior for producing
soluble, folded, and functional recombinant proteins. Reprogramming
is accomplished by overexpressing a negative feedback deficient heat-shock
response
transcription factor before and during overexpression of the protein-of-interest.
The advantage of transcriptional reprogramming versus simply overexpressing
select proteostasis network components (e.g., chaperones and co-chaperones,
which has been explored previously) is that a large number of proteostasis
network components are upregulated at their evolved stoichiometry,
thus maintaining the system capabilities of the proteostasis network
that are currently incompletely understood. Transcriptional proteostasis
network reprogramming mediated by stress-responsive signaling in the
absence of stress should also be useful for protein production in
other cells.
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Affiliation(s)
- Xin Zhang
- Department of Chemistry, ‡Department of Molecular and Experimental
Medicine, and §Department of
Chemical Physiology, ∥The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Yu Liu
- Department of Chemistry, ‡Department of Molecular and Experimental
Medicine, and §Department of
Chemical Physiology, ∥The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Joseph C. Genereux
- Department of Chemistry, ‡Department of Molecular and Experimental
Medicine, and §Department of
Chemical Physiology, ∥The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Chandler Nolan
- Department of Chemistry, ‡Department of Molecular and Experimental
Medicine, and §Department of
Chemical Physiology, ∥The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Meha Singh
- Department of Chemistry, ‡Department of Molecular and Experimental
Medicine, and §Department of
Chemical Physiology, ∥The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Jeffery W. Kelly
- Department of Chemistry, ‡Department of Molecular and Experimental
Medicine, and §Department of
Chemical Physiology, ∥The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
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24
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Lim B, Miyazaki R, Neher S, Siegele DA, Ito K, Walter P, Akiyama Y, Yura T, Gross CA. Heat shock transcription factor σ32 co-opts the signal recognition particle to regulate protein homeostasis in E. coli. PLoS Biol 2013; 11:e1001735. [PMID: 24358019 PMCID: PMC3866087 DOI: 10.1371/journal.pbio.1001735] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Accepted: 10/23/2013] [Indexed: 11/18/2022] Open
Abstract
The bacterial heat shock transcription factor, σ32, maintains proper protein homeostasis only after it is targeted to the inner membrane by the signal recognition particle (SRP), thereby enabling integration of protein folding information from both the cytoplasm and cell membrane. All cells must adapt to rapidly changing conditions. The heat shock response (HSR) is an intracellular signaling pathway that maintains proteostasis (protein folding homeostasis), a process critical for survival in all organisms exposed to heat stress or other conditions that alter the folding of the proteome. Yet despite decades of study, the circuitry described for responding to altered protein status in the best-studied bacterium, E. coli, does not faithfully recapitulate the range of cellular responses in response to this stress. Here, we report the discovery of the missing link. Surprisingly, we found that σ32, the central transcription factor driving the HSR, must be localized to the membrane rather than dispersed in the cytoplasm as previously assumed. Genetic analyses indicate that σ32 localization results from a protein targeting reaction facilitated by the signal recognition particle (SRP) and its receptor (SR), which together comprise a conserved protein targeting machine and mediate the cotranslational targeting of inner membrane proteins to the membrane. SRP interacts with σ32 directly and transports it to the inner membrane. Our results show that σ32 must be membrane-associated to be properly regulated in response to the protein folding status in the cell, explaining how the HSR integrates information from both the cytoplasm and bacterial cell membrane. All cells have to adjust to frequent changes in their environmental conditions. The heat shock response is a signaling pathway critical for survival of all organisms exposed to elevated temperatures. Under such conditions, the heat shock response maintains enzymes and other proteins in a properly folded state. The mechanisms for sensing temperature and the subsequent induction of the appropriate transcriptional response have been extensively studied. Prior to this work, however, the circuitry described in the best studied bacterium E. coli could not fully explain the range of cellular responses that are observed following heat shock. We report the discovery of this missing link. Surprisingly, we find that σ32, a transcription factor that induces gene expression during heat shock, needs to be localized to the membrane, rather than being active as a soluble cytoplasmic protein as previously thought. We show that, equally surprisingly, σ32 is targeted to the membrane by the signal recognition particle (SRP) and its receptor (SR). SRP and SR constitute a conserved protein targeting machine that normally only operates on membrane and periplasmic proteins that contain identifiable signal sequences. Intriguingly, σ32 does not have any canonical signal sequence for export or membrane-integration. Our results indicate that membrane-associated σ32, not soluble cytoplasmic σ32, is the preferred target of regulatory control in response to heat shock. Our new model thus explains how protein folding status from both the cytoplasm and bacterial cell membrane can be integrated to control the heat shock response.
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Affiliation(s)
- Bentley Lim
- Department of Microbiology and Immunology, University of California at San Francisco, San Francisco, California, United States of America
| | - Ryoji Miyazaki
- Institute for Virus Research, Kyoto University, Kyoto, Japan
| | - Saskia Neher
- Department of Biochemistry and Biophysics and Howard Hughes Medical Institute, University of California at San Francisco, San Francisco, California United States of America
| | - Deborah A. Siegele
- Department of Biology, Texas A&M University, College Station, Texas, United States of America
| | - Koreaki Ito
- Faculty of Life Sciences, Kyoto Sangyo University, Kyoto, Japan
| | - Peter Walter
- Department of Biochemistry and Biophysics and Howard Hughes Medical Institute, University of California at San Francisco, San Francisco, California United States of America
| | - Yoshinori Akiyama
- Institute for Virus Research, Kyoto University, Kyoto, Japan
- * E-mail: (Y.A.); (T.Y.); (C.A.G.)
| | - Takashi Yura
- Faculty of Life Sciences, Kyoto Sangyo University, Kyoto, Japan
- * E-mail: (Y.A.); (T.Y.); (C.A.G.)
| | - Carol A. Gross
- Department of Microbiology and Immunology, University of California at San Francisco, San Francisco, California, United States of America
- Department of Cell and Tissue Biology, University of California at San Francisco, San Francisco, California, United States
- * E-mail: (Y.A.); (T.Y.); (C.A.G.)
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25
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Transcription of Ehrlichia chaffeensis genes is accomplished by RNA polymerase holoenzyme containing either sigma 32 or sigma 70. PLoS One 2013; 8:e81780. [PMID: 24278458 PMCID: PMC3836757 DOI: 10.1371/journal.pone.0081780] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Accepted: 10/22/2013] [Indexed: 11/19/2022] Open
Abstract
Bacterial gene transcription is initiated by RNA polymerase containing a sigma factor. To understand gene regulation in Ehrlichia chaffeensis, an important tick-transmitted rickettsiae responsible for human monocytic ehrlichiosis, we initiated studies evaluating the transcriptional machinery of several genes of this organism. We mapped the transcription start sites of 10 genes and evaluated promoters of five genes (groE, dnaK, hup, p28-Omp14 and p28-Omp19 genes). We report here that the RNA polymerase binding elements of E. chaffeensis gene promoters are highly homologous for its only two transcription regulators, sigma 32 and sigma 70, and that gene expression is accomplished by either of the transcription regulators. RNA analysis revealed that although transcripts for both sigma 32 and sigma 70 are upregulated during the early replicative stage, their expression patterns remained similar for the entire replication cycle. We further present evidence demonstrating that the organism’s -35 motifs are essential to transcription initiations. The data suggest that E. chaffeensis gene regulation has evolved to support the organism’s growth, possibly to facilitate its intraphagosomal growth. Considering the limited availability of genetic tools, this study offers a novel alternative in defining gene regulation in E. chaffeensis and other related intracellular pathogens.
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26
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Abstract
Strain tolerance to toxic metabolites is an important trait for many biotechnological applications, such as the production of solvents as biofuels or commodity chemicals. Engineering a complex cellular phenotype, such as solvent tolerance, requires the coordinated and tuned expression of several genes. Using combinations of heat shock proteins (HSPs), we engineered a semisynthetic stress response system in Escherichia coli capable of tolerating high levels of toxic solvents. Simultaneous overexpression of the HSPs GrpE and GroESL resulted in a 2-fold increase in viable cells (CFU) after exposure to 5% (vol/vol) ethanol for 24 h. Co-overexpression of GroESL and ClpB on coexisting plasmids resulted in 1,130%, 78%, and 25% increases in CFU after 24 h in 5% ethanol, 1% n-butanol, and 1% i-butanol, respectively. Co-overexpression of GrpE, GroESL, and ClpB on a single plasmid produced 200%, 390%, and 78% increases in CFU after 24 h in 7% ethanol, 1% n-butanol, or 25% 1,2,4-butanetriol, respectively. Overexpression of other autologous HSPs (DnaK, DnaJ, IbpA, and IbpB) alone or in combinations failed to improve tolerance. Expression levels of HSP genes, tuned through inducible promoters and the plasmid copy number, affected the effectiveness of the engineered stress response system. Taken together, these data demonstrate that tuned co-overexpression of GroES, GroEL, ClpB, and GrpE can be engaged to engineer a semisynthetic stress response system capable of greatly increasing the tolerance of E. coli to solvents and provides a starting platform for engineering customized tolerance to a wide variety of toxic chemicals. Microbial production of useful chemicals is often limited by the toxicity of desired products, feedstock impurities, and undesired side products. Improving tolerance is an essential step in the development of practical platform organisms for production of a wide range of chemicals. By overexpressing autologous heat shock proteins in Escherichia coli, we have developed a modular semisynthetic stress response system capable of improving tolerance to ethanol, n-butanol, and potentially other toxic solvents. Using this system, we demonstrate that a practical stress response system requires both tuning of individual gene components and a reliable framework for gene expression. This system can be used to seek out new interacting partners to improve the tolerance phenotype and can be used in the development of more robust solvent production strains.
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27
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Suzuki H, Ikeda A, Tsuchimoto S, Adachi KI, Noguchi A, Fukumori Y, Kanemori M. Synergistic binding of DnaJ and DnaK chaperones to heat shock transcription factor σ32 ensures its characteristic high metabolic instability: implications for heat shock protein 70 (Hsp70)-Hsp40 mode of function. J Biol Chem 2012; 287:19275-83. [PMID: 22496372 DOI: 10.1074/jbc.m111.331470] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Escherichia coli heat shock transcription factor σ(32) is rapidly degraded by ATP-dependent proteases, such as FtsH and ClpYQ. Although the DnaK chaperone system (DnaK, DnaJ, and GrpE) promotes σ(32) degradation in vivo, the precise mechanism that is involved remains unknown. Our previous results indicated that σ(32) mutants containing amino acid substitution in the N-terminal half of Region 2.1 are markedly stabilized in vivo. Here, we report the further characterization of these mutants by examining purified σ(32) mutants in vitro. Surprisingly, I54A σ(32), a very stable mutant, is more susceptible to ClpYQ and FtsH proteases than wild-type σ(32), indicating that the stability of σ(32) does not always reflect its susceptibility to proteases. Co-precipitation and gel filtration analyses show that purified σ(32) mutants exhibit a reduced affinity for DnaJ, leading to a marked decrease in forming a complex with DnaK in the presence of DnaJ and ATP. Other mutants with modestly increased stability (A50S σ(32) and K51E σ(32)) show an intermediate efficiency of complex formation with DnaK, suggesting that defects in binding to DnaK and DnaJ are well correlated with metabolic stability; effective interaction with DnaK promotes σ(32) degradation in vivo. We argue that the stable and effective interaction of heat shock protein 70 (Hsp70) with a substrate polypeptide may generally require the simultaneous binding of heat shock protein 40 (Hsp40) to distinct sites on the substrate.
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Affiliation(s)
- Hirotaka Suzuki
- School of Natural System, College of Science and Engineering, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
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28
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Roy SS, Patra M, Basu T, Dasgupta R, Bagchi A. Evolutionary analysis of prokaryotic heat-shock transcription regulatory protein σ³². Gene 2012; 495:49-55. [PMID: 22240312 DOI: 10.1016/j.gene.2011.12.043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Accepted: 12/22/2011] [Indexed: 10/14/2022]
Abstract
Heat-stress to any living cell is known to trigger a universal defense response, called heat-shock response, with rapid induction of tens of different heat-shock proteins. Bacterial heat-shock genes are transcribed by the σ(32)-bound RNA polymerase instead of the normal σ(70)-bound RNA polymerase. In this study, the diversity in sequence, variation in secondary structure and function amongst the different functional regions of the proteobacterial σ(32) family of proteins, and their phylogenetic relationships have been analyzed. Bacterial σ(32) proteins can be subdivided into different functional regions which are referred to as regions 2, 3, and 4. There is a great deal of sequence conservation among the functional regions of proteobacterial σ(32) family of proteins though some mutations are also present in these regions. Region 2 is the most conserved one, while region 4 has comparatively more variable sequences. In the present work, we tried to explore the effects of mutations in these regions. Our study suggests that the sequence diversities due to natural mutations in the different regions of proteobacterial σ(32) family lead to different functions. So far, this study is the first bioinformatic approach towards the understanding of the mechanistic details of σ(32) family of proteins using the protein sequence information only. This study therefore may help in elucidating the hitherto unknown molecular mechanism of the functionalities of σ(32)family of proteins.
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Affiliation(s)
- Sourav Singha Roy
- Department of Biochemistry and Biophysics, University of Kalyani, Kalyani, West Bengal, India
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29
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Langklotz S, Baumann U, Narberhaus F. Structure and function of the bacterial AAA protease FtsH. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1823:40-8. [PMID: 21925212 DOI: 10.1016/j.bbamcr.2011.08.015] [Citation(s) in RCA: 131] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2011] [Revised: 08/24/2011] [Accepted: 08/30/2011] [Indexed: 10/17/2022]
Abstract
Proteolysis of regulatory proteins or key enzymes of biosynthetic pathways is a universal mechanism to rapidly adjust the cellular proteome to particular environmental needs. Among the five energy-dependent AAA(+) proteases in Escherichia coli, FtsH is the only essential protease. Moreover, FtsH is unique owing to its anchoring to the inner membrane. This review describes the structural and functional properties of FtsH. With regard to its role in cellular quality control and regulatory circuits, cytoplasmic and membrane substrates of the FtsH protease are depicted and mechanisms of FtsH-dependent proteolysis are discussed.
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Affiliation(s)
- Sina Langklotz
- Lehrstuhl für Biologie der Mikroorganismen, Ruhr-Universität Bochum, Germany
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30
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Meyer AS, Baker TA. Proteolysis in the Escherichia coli heat shock response: a player at many levels. Curr Opin Microbiol 2011; 14:194-9. [PMID: 21353626 DOI: 10.1016/j.mib.2011.02.001] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2010] [Accepted: 02/03/2011] [Indexed: 11/29/2022]
Abstract
Proteolysis is a fundamental process used by all forms of life to maintain homeostasis, as well as to remodel the proteome following environmental changes. Here, we explore recent advances in understanding the role of proteolysis during the heat shock response of Escherichia coli. Proteolysis both regulates and contributes directly to and the heat shock response at multiple different levels, from adjusting the levels of the master heat shock response regulator (σ(32)), to eliminating damaged cellular proteins, to altering the activity of chaperones that refold heat-denatured proteins. Recent results illustrate the complexity of the heat shock response and the pervasive role that proteolysis plays in both the cellular response to heat shock and the subsequent limiting of the response, as cells return to a more 'normal' physiological state.
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Affiliation(s)
- Anne S Meyer
- Department of Biology, MIT, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
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31
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Kobayashi Y, Ohtsu I, Fujimura M, Fukumori F. A mutation in dnaK causes stabilization of the heat shock sigma factor σ32, accumulation of heat shock proteins and increase in toluene-resistance in Pseudomonas putida. Environ Microbiol 2010; 13:2007-17. [PMID: 20880327 DOI: 10.1111/j.1462-2920.2010.02344.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Heat shock gene expression is regulated by the cellular level and activity of the stress sigma factor σ(32) in Gram-negative bacteria. A toluene-resistant, temperature-sensitive derivative strain of Pseudomonas putida KT2442, designated KT2442-R2 (R2), accumulated several heat shock proteins (HSPs) under non-stress conditions. Genome sequencing of strain R2 revealed that its genome contains a number of point mutations, including a CGT to CCT change in dnaK resulting in an Arg445 to Pro substitution in DnaK. DNA microarray and real-time reverse transcription polymerase chain reaction analyses revealed that the mRNA levels of representative hsp genes (e.g. dnaK, htpG and groEL) were upregulated in R2 cells in the stationary phase. Wild-type and R2 cells showed similar heat shock responses at hsp mRNA and HSP levels; however, the σ(32) level in the mutant was not downregulated in the shut-off stage. Strain R2 harbouring plasmid-borne dnaK grew at 37°C, did not accumulate HSPs, and was more sensitive to toluene than strain R2. It is worth to note that that revertant of R2 able to grow at 37°C were isolated and exhibited a replacement of Pro445 by Ser or Leu in DnaK. Thus, the mutation in dnaK causes the temperature-sensitive phenotype, improper stabilization of σ(32) leading to HSP accumulation and increased toluene resistance in strain R2.
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Affiliation(s)
- Yuka Kobayashi
- Graduate School of Life Sciences, Toyo University, Gunma, Japan
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32
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Godman CA, Chheda KP, Hightower LE, Perdrizet G, Shin DG, Giardina C. Hyperbaric oxygen induces a cytoprotective and angiogenic response in human microvascular endothelial cells. Cell Stress Chaperones 2010; 15:431-42. [PMID: 19949909 PMCID: PMC3082642 DOI: 10.1007/s12192-009-0159-0] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2009] [Revised: 11/02/2009] [Accepted: 11/04/2009] [Indexed: 11/29/2022] Open
Abstract
A genome-wide microarray analysis of gene expression was carried out on human microvascular endothelial cells (HMEC-1) exposed to hyperbaric oxygen treatment (HBOT) under conditions that approximated clinical settings. Highly up-regulated genes included immediate early transcription factors (FOS, FOSB, and JUNB) and metallothioneins. Six molecular chaperones were also up-regulated immediately following HBOT, and all of these have been implicated in protein damage control. Pathway analysis programs identified the Nrf-2-mediated oxidative stress response as one of the primary responders to HBOT. Several of the microarray changes in the Nrf2 pathway and a molecular chaperone were validated using quantitative PCR. For all of the genes tested (Nrf2, HMOX1, HSPA1A, M1A, ACTC1, and FOS), HBOT elicited large responses, whereas changes were minimal following treatment with 100% O(2) in the absence of elevated pressure. The increased expression of immediate early and cytoprotective genes corresponded with an HBOT-induced increase in cell proliferation and oxidative stress resistance. In addition, HBOT treatment enhanced endothelial tube formation on Matrigel plates, with particularly dramatic effects observed following two daily HBO treatments. Understanding how HBOT influences gene expression changes in endothelial cells may be beneficial for improving current HBOT-based wound-healing protocols. These data also point to other potential HBOT applications where stimulating protection and repair of the endothelium would be beneficial, such as patient preconditioning prior to major surgery.
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Affiliation(s)
- Cassandra A Godman
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT, USA.
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33
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Kanai T, Takedomi S, Fujiwara S, Atomi H, Imanaka T. Identification of the Phr-dependent heat shock regulon in the hyperthermophilic archaeon, Thermococcus kodakaraensis. J Biochem 2009; 147:361-70. [PMID: 19887527 DOI: 10.1093/jb/mvp177] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The hyperthermophilic archaeon Thermococcus kodakaraensis harbors a putative transcriptional regulator (Tk-Phr) that is orthologous to the Pyrococcus furiosus Phr (Pf-Phr). Pf-Phr, a transcriptional regulator, represses genes encoding the small heat shock protein (sHSP), AAA(+) ATPase and Pf-Phr itself under normal growth temperatures. Here we constructed a gene disruption strain of Tk-Phr (strain KHR1). KHR1 cells showed similar specific growth rates with those of the wild-type strain under various temperatures. A whole genome microarray analysis was performed between KHR1 and wild-type cells grown at 80 degrees C. Transcript levels of more than 20 genes were significantly higher in KHR1 cells. Most genes contained a sequence motif virtually identical to that of Pf-Phr in their 5'-flanking regions. The Tk-Phr regulon included genes encoding sHSP, AAA(+) ATPase, prefoldin, RecA superfamily ATPase and Tip49. On the other hand, more than half of the members in the regulon encoded conserved/hypothetical proteins, raising the possibility that these proteins participate in unidentified processes of the heat shock response. In contrast, Tk-Phr deletion did not lead to dramatic increase in transcript and protein levels of a chaperonin (CpkB) previously shown to respond to heat shock, suggesting the presence of a second, Phr-independent heat shock response mechanism in T. kodakaraensis.
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Affiliation(s)
- Tamotsu Kanai
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto, Japan
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Narberhaus F, Obrist M, Führer F, Langklotz S. Degradation of cytoplasmic substrates by FtsH, a membrane-anchored protease with many talents. Res Microbiol 2009; 160:652-9. [DOI: 10.1016/j.resmic.2009.08.011] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2009] [Revised: 08/17/2009] [Accepted: 08/17/2009] [Indexed: 12/01/2022]
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35
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Grall N, Livny J, Waldor M, Barel M, Charbit A, Meibom KL. Pivotal role of the Francisella tularensis heat-shock sigma factor RpoH. MICROBIOLOGY-SGM 2009; 155:2560-2572. [PMID: 19443547 DOI: 10.1099/mic.0.029058-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Francisella tularensis is a highly infectious pathogen that infects animals and humans to cause the disease tularemia. The primary targets of this bacterium are macrophages, in which it replicates in the cytoplasm after escaping the initial phagosomal compartment. The ability to replicate within macrophages relies on the tightly regulated expression of a series of genes. One of the most commonly used means of coordinating the regulation of multiple genes in bacteria consists of the association of dedicated alternative sigma factors with the core of the RNA polymerase (RNAP). In silico analysis of the F. tularensis LVS genome led us to identify, in addition to the genes encoding the RNAP core (comprising the alpha1, alpha2, beta, beta' and omega subunits), one gene (designated rpoD) encoding the major sigma factor sigma(70), and a unique gene (FTL_0851) encoding a putative alternative sigma factor homologue of the sigma(32) heat-shock family (designated rpoH). Hence, F. tularensis represents one of the minority of bacterial species that possess only one or no alternative sigma factor in addition to the main factor sigma(70). In the present work, we show that FTL_0851 encodes a genuine sigma(32) factor. Transcriptomic analyses of the F. tularensis LVS heat-stress response allowed the identification of a series of orthologues of known heat-shock genes (including those for Hsp40, GroEL, GroES, DnaK, DnaJ, GrpE, ClpB and ClpP) and a number of genes implicated in Francisella virulence. A bioinformatic analysis was used to identify genes preceded by a putative sigma(32)-binding site, revealing both similarities to and differences from RpoH-mediated gene expression in Escherichia coli. Our results suggest that RpoH is an essential protein of F. tularensis, and positively regulates a subset of genes involved in the heat-shock response.
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Affiliation(s)
- Nathalie Grall
- INSERM, U570, Unit of Pathogenesis of Systemic Infections, F-75015 Paris, France.,Université Paris Descartes, Faculté de Médecine Necker-Enfants Malades, F-75015 Paris, France
| | - Jonathan Livny
- Channing Laboratories, Brigham and Women's Hospital, Harvard Medical School, 181 Longwood Avenue, Boston, MA 02115, USA
| | - Matthew Waldor
- Howard Hughes Medical Institute, 4000 Jones Bridge Road, Chevy Chase, MD 20815-6789, USA.,Channing Laboratories, Brigham and Women's Hospital, Harvard Medical School, 181 Longwood Avenue, Boston, MA 02115, USA
| | - Monique Barel
- INSERM, U570, Unit of Pathogenesis of Systemic Infections, F-75015 Paris, France.,Université Paris Descartes, Faculté de Médecine Necker-Enfants Malades, F-75015 Paris, France
| | - Alain Charbit
- INSERM, U570, Unit of Pathogenesis of Systemic Infections, F-75015 Paris, France.,Université Paris Descartes, Faculté de Médecine Necker-Enfants Malades, F-75015 Paris, France
| | - Karin L Meibom
- INSERM, U570, Unit of Pathogenesis of Systemic Infections, F-75015 Paris, France.,Université Paris Descartes, Faculté de Médecine Necker-Enfants Malades, F-75015 Paris, France
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Rasouly A, Ron EZ. Interplay between the heat shock response and translation in Escherichia coli. Res Microbiol 2009; 160:288-96. [PMID: 19379808 DOI: 10.1016/j.resmic.2009.03.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2009] [Revised: 03/30/2009] [Accepted: 03/30/2009] [Indexed: 12/11/2022]
Abstract
It is widely accepted that the heat shock response is critical for quality control of mature proteins. This function is carried out mainly by chaperones and proteases. Recently, a new group of conserved heat shock proteins essential for growth at high temperature has been characterized. These proteins are involved in regulating and maintaining efficient translation under heat shock.
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Affiliation(s)
- Aviram Rasouly
- Department of Molecular Microbiology and Biotechnology, Faculty of Life Sciences, Tel Aviv University, Levanon St, Tel Aviv 69978, Israel
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Koo BM, Rhodius VA, Campbell EA, Gross CA. Dissection of recognition determinants of Escherichia coli sigma32 suggests a composite -10 region with an 'extended -10' motif and a core -10 element. Mol Microbiol 2009; 72:815-29. [PMID: 19400791 DOI: 10.1111/j.1365-2958.2009.06690.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Sigma32 controls expression of heat shock genes in Escherichia coli and is widely distributed in proteobacteria. The distinguishing feature of sigma32 promoters is a long -10 region (CCCCATNT) whose tetra-C motif is important for promoter activity. Using alanine-scanning mutagenesis of sigma32 and in vivo and in vitro assays, we identified promoter recognition determinants of this motif. The most downstream C (-13) is part of the -10 motif; our work confirms and extends recognition determinants of -13C. Most importantly, our work suggests that the two upstream Cs (-16, -15) constitute an 'extended -10' recognition motif that is recognized by K130, a residue universally conserved in beta- and gamma-proteobacteria. This residue is located in the alpha-helix of sigmaDomain 3 that mediates recognition of the extended -10 promoter motif in other sigmas. K130 is not conserved in alpha- and delta-/epsilon-proteobacteria and we found that sigma32 from the alpha-proteobacterium Caulobacter crescentus does not need the extended -10 motif for high promoter activity. This result supports the idea that K130 mediates extended -10 recognition. Sigma32 is the first Group 3 sigma shown to use the 'extended -10' recognition motif.
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Affiliation(s)
- Byoung-Mo Koo
- Department of Microbiology and Immunology, University of California at San Francisco, San Francisco, CA 94158, USA
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Growth phase- and cell division-dependent activation and inactivation of the {sigma}32 regulon in Escherichia coli. J Bacteriol 2008; 191:1695-702. [PMID: 19114495 DOI: 10.1128/jb.01536-08] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Alternative sigma factors allow bacteria to reprogram global transcription rapidly and to adapt to changes in the environment. Here we report on growth- and cell division-dependent sigma(32) regulon activity in Escherichia coli in batch culture. By analyzing sigma(32) expression in growing cells, an increase in sigma(32) protein levels is observed during the first round of cell division after exit from stationary phase. Increased sigma(32) protein levels result from transcriptional activation of the rpoH gene. After the first round of bulk cell division, rpoH transcript levels and sigma(32) protein levels decrease again. The late-logarithmic phase and the transition to stationary phase are accompanied by a second increase in sigma(32) levels and enhanced stability of sigma(32) protein but not by enhanced transcription of rpoH. Throughout growth, sigma(32) target genes show expression patterns consistent with oscillating sigma(32) protein levels. However, during the transition to early-stationary phase, despite high sigma(32) protein levels, the transcription of sigma(32) target genes is downregulated, suggesting functional inactivation of sigma(32). It is deduced from these data that there may be a link between sigma(32) regulon activity and cell division events. Further support for this hypothesis is provided by the observation that in cells in which FtsZ is depleted, sigma(32) regulon activation is suppressed.
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Obrist M, Langklotz S, Milek S, Führer F, Narberhaus F. Region C of the Escherichia coli heat shock sigma factor RpoH (σ32) contains a turnover element for proteolysis by the FtsH protease. FEMS Microbiol Lett 2008; 290:199-208. [DOI: 10.1111/j.1574-6968.2008.01423.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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40
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Convergence of molecular, modeling, and systems approaches for an understanding of the Escherichia coli heat shock response. Microbiol Mol Biol Rev 2008; 72:545-54. [PMID: 18772288 DOI: 10.1128/mmbr.00007-08] [Citation(s) in RCA: 184] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The heat shock response (HSR) is a homeostatic response that maintains the proper protein-folding environment in the cell. This response is universal, and many of its components are well conserved from bacteria to humans. In this review, we focus on the regulation of one of the most well-characterized HSRs, that of Escherichia coli. We show that even for this simple model organism, we still do not fully understand the central component of heat shock regulation, a chaperone-mediated negative feedback loop. In addition, we review other components that contribute to the regulation of the HSR in E. coli and discuss how these additional components contribute to regulation. Finally, we discuss recent genomic experiments that reveal additional functional aspects of the HSR.
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Rodriguez F, Arsène-Ploetze F, Rist W, Rüdiger S, Schneider-Mergener J, Mayer MP, Bukau B. Molecular Basis for Regulation of the Heat Shock Transcription Factor σ32 by the DnaK and DnaJ Chaperones. Mol Cell 2008; 32:347-58. [DOI: 10.1016/j.molcel.2008.09.016] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2007] [Revised: 04/23/2008] [Accepted: 09/26/2008] [Indexed: 10/21/2022]
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42
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Rich RL, Myszka DG. Survey of the year 2007 commercial optical biosensor literature. J Mol Recognit 2008; 21:355-400. [DOI: 10.1002/jmr.928] [Citation(s) in RCA: 144] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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43
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Huo YX, Rosenthal AZ, Gralla JD. General stress response signalling: unwrapping transcription complexes by DNA relaxation via the sigma38 C-terminal domain. Mol Microbiol 2008; 70:369-78. [PMID: 18761624 DOI: 10.1111/j.1365-2958.2008.06412.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Escherichia coli responds to stress by a combination of specific and general transcription signalling pathways. The general pathways typically require the master stress regulator sigma38 (rpoS). Here we show that the signalling from multiple stresses that relax DNA is processed by a non-conserved eight-amino-acid tail of the sigma 38 C-terminal domain. By contrast, responses to two stresses that accumulate potassium glutamate do not rely on this short tail, but still require the overall C-terminal domain. In vitro transcription and footprinting studies suggest that multiple stresses can target a poised RNA polymerase and activate it by unwrapping DNA from a nucleosome-like state, allowing the RNA polymerase to escape into productive mode. This transition can be accomplished by either the DNA relaxation or potassium glutamate accumulation that characterizes many stresses.
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Affiliation(s)
- Yi-Xin Huo
- Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, PO Box 951569, Los Angeles, CA 90095, USA
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