1
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Bray AS, Broberg CA, Hudson AW, Wu W, Nagpal RK, Islam M, Valencia-Bacca JD, Shahid F, Hernandez GE, Nutter NA, Walker KA, Bennett EF, Young TM, Barnes AJ, Ornelles DA, Miller VL, Zafar MA. Klebsiella pneumoniae employs a type VI secretion system to overcome microbiota-mediated colonization resistance. Nat Commun 2025; 16:940. [PMID: 39843522 PMCID: PMC11754592 DOI: 10.1038/s41467-025-56309-8] [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: 02/13/2024] [Accepted: 01/15/2025] [Indexed: 01/24/2025] Open
Abstract
Microbial species must compete for space and nutrients to persist in the gastrointestinal (GI) tract, and our understanding of the complex pathobiont-microbiota interactions is far from complete. Klebsiella pneumoniae, a problematic, often drug-resistant nosocomial pathogen, can colonize the GI tract asymptomatically, serving as an infection reservoir. To provide insight on how K. pneumoniae interacts with the resident gut microbiome, we conduct a transposon mutagenesis screen using a murine model of GI colonization with an intact microbiota. Among the genes identified were those encoding a type VI secretion system (T6SS), which mediates contact-dependent killing of gram-negative bacteria. From several approaches, we demonstrate that the T6SS is critical for K. pneumoniae gut colonization. Metagenomics and in vitro killing assays reveal that K. pneumoniae reduces Betaproteobacteria species in a T6SS-dependent manner, thus identifying specific species targeted by K. pneumoniae. We further show that T6SS gene expression is controlled by several transcriptional regulators and that expression only occurs in vitro under conditions that mimic the gut environment. By enabling K. pneumoniae to thrive in the gut, the T6SS indirectly contributes to the pathogenic potential of this organism. These observations advance our molecular understanding of how K. pneumoniae successfully colonizes the GI tract.
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Affiliation(s)
- Andrew S Bray
- Department of Microbiology and Immunology, Wake Forest School of Medicine, Winston Salem, NC, USA
| | - Christopher A Broberg
- Department of Microbiology and Immunology, University of North Carolina School of Medicine, Chapel Hill, NC, USA
| | - Andrew W Hudson
- Department of Microbiology and Immunology, Wake Forest School of Medicine, Winston Salem, NC, USA
| | - Weisheng Wu
- BRCF Bioinformatics Core, University of Michigan, Ann Arbor, MI, USA
| | - Ravinder K Nagpal
- Department of Nutrition & Integrative Physiology, Florida State University College of Health and Human Sciences, Tallahassee, FL, USA
| | - Maidul Islam
- Department of Microbiology and Immunology, Wake Forest School of Medicine, Winston Salem, NC, USA
| | - Juan D Valencia-Bacca
- Department of Microbiology and Immunology, Wake Forest School of Medicine, Winston Salem, NC, USA
| | - Fawaz Shahid
- Wake Forest University, Winston Salem, Winston Salem, NC, USA
| | - Giovanna E Hernandez
- Department of Microbiology and Immunology, Wake Forest School of Medicine, Winston Salem, NC, USA
| | - Noah A Nutter
- Department of Microbiology and Immunology, Wake Forest School of Medicine, Winston Salem, NC, USA
| | - Kimberly A Walker
- Department of Microbiology and Immunology, University of North Carolina School of Medicine, Chapel Hill, NC, USA
| | - Emma F Bennett
- Department of Microbiology and Immunology, Wake Forest School of Medicine, Winston Salem, NC, USA
| | - Taylor M Young
- Department of Microbiology and Immunology, Wake Forest School of Medicine, Winston Salem, NC, USA
| | - Andrew J Barnes
- Department of Microbiology and Immunology, Wake Forest School of Medicine, Winston Salem, NC, USA
| | - David A Ornelles
- Department of Microbiology and Immunology, Wake Forest School of Medicine, Winston Salem, NC, USA
| | - Virginia L Miller
- Department of Microbiology and Immunology, University of North Carolina School of Medicine, Chapel Hill, NC, USA
- Department of Genetics, University of North Carolina School of Medicine, Chapel Hill, NC, USA
| | - M Ammar Zafar
- Department of Microbiology and Immunology, Wake Forest School of Medicine, Winston Salem, NC, USA.
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA, USA.
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2
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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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3
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Petrova O, Semenova E, Parfirova O, Tsers I, Gogoleva N, Gogolev Y, Nikolaichik Y, Gorshkov V. RpoS-Regulated Genes and Phenotypes in the Phytopathogenic Bacterium Pectobacterium atrosepticum. Int J Mol Sci 2023; 24:17348. [PMID: 38139177 PMCID: PMC10743746 DOI: 10.3390/ijms242417348] [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: 11/07/2023] [Revised: 12/04/2023] [Accepted: 12/08/2023] [Indexed: 12/24/2023] Open
Abstract
The alternative sigma factor RpoS is considered to be one of the major regulators providing stress resistance and cross-protection in bacteria. In phytopathogenic bacteria, the effects of RpoS have not been analyzed with regard to cross-protection, and genes whose expression is directly or indirectly controlled by RpoS have not been determined at the whole-transcriptome level. Our study aimed to determine RpoS-regulated genes and phenotypes in the phytopathogenic bacterium Pectobacterium atrosepticum. Knockout of the rpoS gene in P. atrosepticum affected the long-term starvation response, cross-protection, and virulence toward plants with enhanced immune status. The whole-transcriptome profiles of the wild-type P. atrosepticum strain and its ΔrpoS mutant were compared under different experimental conditions, and functional gene groups whose expression was affected by RpoS were determined. The RpoS promoter motif was inferred within the promoter regions of the genes affected by rpoS deletion, and the P. atrosepticum RpoS regulon was predicted. Based on RpoS-controlled phenotypes, transcriptome profiles, and RpoS regulon composition, the regulatory role of RpoS in P. atrosepticum is discussed.
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Affiliation(s)
- Olga Petrova
- Kazan Institute of Biochemistry and Biophysics, Federal Research Center “Kazan Scientific Center of the Russian Academy of Sciences”, 420111 Kazan, Russia; (O.P.); (E.S.); (O.P.); (I.T.); (N.G.); (Y.G.)
| | - Elizaveta Semenova
- Kazan Institute of Biochemistry and Biophysics, Federal Research Center “Kazan Scientific Center of the Russian Academy of Sciences”, 420111 Kazan, Russia; (O.P.); (E.S.); (O.P.); (I.T.); (N.G.); (Y.G.)
| | - Olga Parfirova
- Kazan Institute of Biochemistry and Biophysics, Federal Research Center “Kazan Scientific Center of the Russian Academy of Sciences”, 420111 Kazan, Russia; (O.P.); (E.S.); (O.P.); (I.T.); (N.G.); (Y.G.)
| | - Ivan Tsers
- Kazan Institute of Biochemistry and Biophysics, Federal Research Center “Kazan Scientific Center of the Russian Academy of Sciences”, 420111 Kazan, Russia; (O.P.); (E.S.); (O.P.); (I.T.); (N.G.); (Y.G.)
| | - Natalia Gogoleva
- Kazan Institute of Biochemistry and Biophysics, Federal Research Center “Kazan Scientific Center of the Russian Academy of Sciences”, 420111 Kazan, Russia; (O.P.); (E.S.); (O.P.); (I.T.); (N.G.); (Y.G.)
| | - Yuri Gogolev
- Kazan Institute of Biochemistry and Biophysics, Federal Research Center “Kazan Scientific Center of the Russian Academy of Sciences”, 420111 Kazan, Russia; (O.P.); (E.S.); (O.P.); (I.T.); (N.G.); (Y.G.)
- Institute of Fundamental Medicine and Biology, Kazan Federal University, 420008 Kazan, Russia
| | - Yevgeny Nikolaichik
- Department of Molecular Biology, Belarusian State University, 220030 Minsk, Belarus;
| | - Vladimir Gorshkov
- Kazan Institute of Biochemistry and Biophysics, Federal Research Center “Kazan Scientific Center of the Russian Academy of Sciences”, 420111 Kazan, Russia; (O.P.); (E.S.); (O.P.); (I.T.); (N.G.); (Y.G.)
- Institute of Fundamental Medicine and Biology, Kazan Federal University, 420008 Kazan, Russia
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4
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Adams J, Hoang J, Petroni E, Ashby E, Hardin J, Stoebel DM. The timing of transcription of RpoS-dependent genes varies across multiple stresses in Escherichia coli K-12. mSystems 2023; 8:e0066323. [PMID: 37623321 PMCID: PMC10654073 DOI: 10.1128/msystems.00663-23] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 07/14/2023] [Indexed: 08/26/2023] Open
Abstract
IMPORTANCE Bacteria adapt to changing environments by altering the transcription of their genes. Specific proteins can regulate these changes. This study explored how a single protein called RpoS controls how many genes change expression during adaptation to three stresses. We found that: (i) RpoS is responsible for activating different genes in different stresses; (ii) that during a stress, the timing of gene activation depends on the what stress it is; and (iii) that how much RpoS a gene needs in order to be activated can predict when that gene will be activated during the stress of stationary phase.
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Affiliation(s)
- Josephine Adams
- Department of Biology, Harvey Mudd College, Claremont, California, USA
| | - Johnson Hoang
- Department of Biology, Harvey Mudd College, Claremont, California, USA
| | - Emily Petroni
- Department of Biology, Harvey Mudd College, Claremont, California, USA
| | - Ethan Ashby
- Department of Mathematics and Statistics, Pomona College, Claremont, California, USA
| | - Johanna Hardin
- Department of Mathematics and Statistics, Pomona College, Claremont, California, USA
| | - Daniel M. Stoebel
- Department of Biology, Harvey Mudd College, Claremont, California, USA
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5
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Westfall AK, Gopalan SS, Perry BW, Adams RH, Saviola AJ, Mackessy SP, Castoe TA. Single-Cell Heterogeneity in Snake Venom Expression Is Hardwired by Co-Option of Regulators from Progressively Activated Pathways. Genome Biol Evol 2023; 15:evad109. [PMID: 37311204 PMCID: PMC10289209 DOI: 10.1093/gbe/evad109] [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: 03/06/2023] [Revised: 05/31/2023] [Accepted: 06/07/2023] [Indexed: 06/15/2023] Open
Abstract
The ubiquitous cellular heterogeneity underlying many organism-level phenotypes raises questions about what factors drive this heterogeneity and how these complex heterogeneous systems evolve. Here, we use single-cell expression data from a Prairie rattlesnake (Crotalus viridis) venom gland to evaluate hypotheses for signaling networks underlying snake venom regulation and the degree to which different venom gene families have evolutionarily recruited distinct regulatory architectures. Our findings suggest that snake venom regulatory systems have evolutionarily co-opted trans-regulatory factors from extracellular signal-regulated kinase and unfolded protein response pathways that specifically coordinate expression of distinct venom toxins in a phased sequence across a single population of secretory cells. This pattern of co-option results in extensive cell-to-cell variation in venom gene expression, even between tandemly duplicated paralogs, suggesting this regulatory architecture has evolved to circumvent cellular constraints. While the exact nature of such constraints remains an open question, we propose that such regulatory heterogeneity may circumvent steric constraints on chromatin, cellular physiological constraints (e.g., endoplasmic reticulum stress or negative protein-protein interactions), or a combination of these. Regardless of the precise nature of these constraints, this example suggests that, in some cases, dynamic cellular constraints may impose previously unappreciated secondary constraints on the evolution of gene regulatory networks that favors heterogeneous expression.
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Affiliation(s)
| | | | - Blair W Perry
- Department of Biology, The University of Texas Arlington, Texas, USA
- School of Biological Sciences, Washington State University, Pullman, Washington, USA
| | - Richard H Adams
- Department of Entomology and Plant Pathology, University of Arkansas, Fayetteville, USA
| | - Anthony J Saviola
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver, Aurora, USA
| | - Stephen P Mackessy
- School of Biological Sciences, University of Northern Colorado, Greeley, USA
| | - Todd A Castoe
- Department of Biology, The University of Texas Arlington, Texas, USA
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6
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Grassmann AA, Tokarz R, Golino C, McLain MA, Groshong AM, Radolf JD, Caimano MJ. BosR and PlzA reciprocally regulate RpoS function to sustain Borrelia burgdorferi in ticks and mammals. J Clin Invest 2023; 133:e166710. [PMID: 36649080 PMCID: PMC9974103 DOI: 10.1172/jci166710] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Accepted: 01/10/2023] [Indexed: 01/18/2023] Open
Abstract
The RNA polymerase alternative σ factor RpoS in Borrelia burgdorferi (Bb), the Lyme disease pathogen, is responsible for programmatic-positive and -negative gene regulation essential for the spirochete's dual-host enzootic cycle. RpoS is expressed during tick-to-mammal transmission and throughout mammalian infection. Although the mammalian-phase RpoS regulon is well described, its counterpart during the transmission blood meal is unknown. Here, we used Bb-specific transcript enrichment by tick-borne disease capture sequencing (TBDCapSeq) to compare the transcriptomes of WT and ΔrpoS Bb in engorged nymphs and following mammalian host-adaptation within dialysis membrane chambers. TBDCapSeq revealed dramatic changes in the contours of the RpoS regulon within ticks and mammals and further confirmed that RpoS-mediated repression is specific to the mammalian-phase of Bb's enzootic cycle. We also provide evidence that RpoS-dependent gene regulation, including repression of tick-phase genes, is required for persistence in mice. Comparative transcriptomics of engineered Bb strains revealed that the Borrelia oxidative stress response regulator (BosR), a noncanonical Fur family member, and the cyclic diguanosine monophosphate (c-di-GMP) effector PlzA reciprocally regulate the function of RNA polymerase complexed with RpoS. BosR is required for RpoS-mediated transcription activation and repression in addition to its well-defined role promoting transcription of rpoS by the RNA polymerase alternative σ factor RpoN. During transmission, ligand-bound PlzA antagonizes RpoS-mediated repression, presumably acting through BosR.
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Affiliation(s)
| | - Rafal Tokarz
- Center for Infection and Immunity and
- Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, New York, USA
| | - Caroline Golino
- Department of Medicine, UConn Health, Farmington, Connecticut, USA
| | | | - Ashley M. Groshong
- Department of Medicine, UConn Health, Farmington, Connecticut, USA
- Department of Pediatrics
| | - Justin D. Radolf
- Department of Medicine, UConn Health, Farmington, Connecticut, USA
- Department of Pediatrics
- Department of Molecular Biology and Biophysics
- Department of Genetics and Genome Sciences, and
- Department of Immunology, UConn Health, Farmington, Connecticut, USA
| | - Melissa J. Caimano
- Department of Medicine, UConn Health, Farmington, Connecticut, USA
- Department of Pediatrics
- Department of Molecular Biology and Biophysics
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7
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Hudson AW, Barnes AJ, Bray AS, Ornelles DA, Zafar MA. Klebsiella pneumoniae l-Fucose Metabolism Promotes Gastrointestinal Colonization and Modulates Its Virulence Determinants. Infect Immun 2022; 90:e0020622. [PMID: 36129299 PMCID: PMC9584338 DOI: 10.1128/iai.00206-22] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Colonization of the gastrointestinal (GI) tract by Klebsiella pneumoniae is generally considered asymptomatic. However, gut colonization allows K. pneumoniae to either translocate to sterile site within the same host or transmit through the fecal-oral route to another host. K. pneumoniae gut colonization is poorly understood, but knowledge of this first step toward infection and spread is critical for combatting its disease manifestations. K. pneumoniae must overcome colonization resistance (CR) provided by the host microbiota to establish itself within the gut. One such mechanism of CR is through nutrient competition. Pathogens that metabolize a broad range of substrates have the ability to bypass nutrient competition and overcome CR. Herein, we demonstrate that in response to mucin-derived fucose, the conserved fucose metabolism operon (fuc) of K. pneumoniae is upregulated in the murine gut, and we subsequently show that fucose metabolism promotes robust gut colonization. Growth studies using cecal filtrate as a proxy for the gut lumen illustrate the growth advantage that the fuc operon provides K. pneumoniae. We further show that fucose metabolism allows K. pneumoniae to be competitive with a commensal Escherichia coli isolate (Nissle). However, Nissle is eventually able to outcompete K. pneumoniae, suggesting that it can be utilized to enhance CR. Finally, we observed that fucose metabolism positively modulates hypermucoviscosity, autoaggregation, and biofilm formation but not capsule biogenesis. Together, these insights enhance our understanding of the role of alternative carbon sources in K. pneumoniae gut colonization and the complex relationship between metabolism and virulence in this species.
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Affiliation(s)
- Andrew W. Hudson
- Department of Microbiology and Immunology, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
| | - Andrew J. Barnes
- Department of Microbiology and Immunology, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
| | - Andrew S. Bray
- Department of Microbiology and Immunology, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
| | - David A. Ornelles
- Department of Microbiology and Immunology, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
| | - M. Ammar Zafar
- Department of Microbiology and Immunology, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
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8
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John J, Jabbar J, Badjatia N, Rossi MJ, Lai WKM, Pugh BF. Genome-wide promoter assembly in E. coli measured at single-base resolution. Genome Res 2022; 32:878-892. [PMID: 35483960 PMCID: PMC9104697 DOI: 10.1101/gr.276544.121] [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: 12/28/2021] [Accepted: 03/19/2022] [Indexed: 11/04/2022]
Abstract
When detected at single-base-pair resolution, the genome-wide location, occupancy level, and structural organization of DNA-binding proteins provide mechanistic insights into genome regulation. Here we use ChIP-exo to provide a near-base-pair resolution view of the epigenomic organization of the Escherichia coli transcription machinery and nucleoid structural proteins at the time when cells are growing exponentially and upon rapid reprogramming (acute heat shock). We examined the site specificity of three sigma factors (RpoD/σ70, RpoH/σ32, and RpoN/σ54), RNA polymerase (RNAP or RpoA, -B, -C), and two nucleoid proteins (Fis and IHF). We suggest that DNA shape at the flanks of cognate motifs helps drive site specificity. We find that although RNAP and sigma factors occupy active cognate promoters, RpoH and RpoN can occupy quiescent promoters without the presence of RNAP. Thus, promoter-bound sigma factors can be triggered to recruit RNAP by a mechanism that is distinct from an obligatory cycle of free sigma binding RNAP followed by promoter binding. These findings add new dimensions to how sigma factors achieve promoter specificity through DNA sequence and shape, and further define mechanistic steps in regulated genome-wide assembly of RNAP at promoters in E. coli.
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Affiliation(s)
- Jordan John
- Center for Eukaryotic Gene Regulation, Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Javaid Jabbar
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, USA
| | - Nitika Badjatia
- Center for Eukaryotic Gene Regulation, Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Matthew J Rossi
- Center for Eukaryotic Gene Regulation, Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - William K M Lai
- Center for Eukaryotic Gene Regulation, Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, USA
- Department of Computational Biology, Cornell University, Ithaca, New York 14850, USA
| | - B Franklin Pugh
- Center for Eukaryotic Gene Regulation, Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, USA
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9
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Kim SI, Kim E, Yoon H. σ S-Mediated Stress Response Induced by Outer Membrane Perturbation Dampens Virulence in Salmonella enterica serovar Typhimurium. Front Microbiol 2021; 12:750940. [PMID: 34659184 PMCID: PMC8516096 DOI: 10.3389/fmicb.2021.750940] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Accepted: 08/30/2021] [Indexed: 12/13/2022] Open
Abstract
Salmonella alters cellular processes as a strategy to improve its intracellular fitness during host infection. Alternative σ factors are known to rewire cellular transcriptional regulation in response to environmental stressors. σs factor encoded by the rpoS gene is a key regulator required for eliciting the general stress response in many proteobacteria. In this study, Salmonella Typhimurium deprived of an outer membrane protein YcfR was attenuated in intracellular survival and exhibited downregulation in Salmonella pathogenicity island-2 (SPI-2) genes. This decreased SPI-2 expression caused by the outer membrane perturbation was abolished in the absence of rpoS. Interestingly, regardless of the defects in the outer membrane integrity, RpoS overproduction decreased transcription from the common promoter of ssrA and ssrB, which encode a two-component regulatory system for SPI-2. RpoS was found to compete with RpoD for binding to the PssrA region, and its binding activity with RNA polymerase (RNAP) to form Eσs holoenzyme was stimulated by the small regulatory protein Crl. This study demonstrates that Salmonella undergoing RpoS-associated stress responses due to impaired envelope integrity may reciprocally downregulate the expression of SPI-2 genes to reduce its virulence.
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Affiliation(s)
- Seul I Kim
- Department of Molecular Science and Technology, Ajou University, Suwon, South Korea
| | - Eunsuk Kim
- Department of Molecular Science and Technology, Ajou University, Suwon, South Korea
| | - Hyunjin Yoon
- Department of Molecular Science and Technology, Ajou University, Suwon, South Korea.,Department of Applied Chemistry and Biological Engineering, Ajou University, Suwon, South Korea
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10
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Regulatory small RNA, Qrr2 is expressed independently of sigma factor-54 and can function as the sole Qrr sRNA to control quorum sensing in Vibrio parahaemolyticus. J Bacteriol 2021; 204:e0035021. [PMID: 34633869 DOI: 10.1128/jb.00350-21] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacterial cells alter gene expression in response to changes in population density in a process called quorum sensing (QS). In Vibrio harveyi, LuxO, a low cell density activator of sigma factor-54 (RpoN), is required for transcription of five non-coding regulatory sRNAs, Qrr1-Qrr5, which each repress translation of the master QS regulator LuxR. Vibrio parahaemolyticus, the leading cause of bacterial seafood-borne gastroenteritis, also contains five Qrr sRNAs that control OpaR (the LuxR homolog), controlling capsule polysaccharide (CPS), motility, and metabolism. We show that in a ΔluxO deletion mutant, opaR was de-repressed and CPS and biofilm were produced. However, in a ΔrpoN mutant, opaR was repressed, no CPS was produced, and less biofilm production was observed compared to wild type. To determine why opaR was repressed, expression analysis in ΔluxO showed all five qrr genes were repressed, while in ΔrpoN the qrr2 gene was significantly de-repressed. Reporter assays and mutant analysis showed Qrr2 sRNA can act alone to control OpaR. Bioinformatics analysis identified a sigma-70 (RpoD) -35 -10 promoter overlapping the canonical sigma-54 (RpoN) -24 -12 promoter in the qrr2 regulatory region. The qrr2 sigma-70 promoter element was also present in additional Vibrio species indicating it is widespread. Mutagenesis of the sigma-70 -10 promoter site in the ΔrpoN mutant background, resulted in repression of qrr2. Analysis of qrr quadruple deletion mutants, in which only a single qrr gene is present, showed that only Qrr2 sRNA can act independently to regulate opaR. Mutant and expression data also demonstrated that RpoN and the global regulator, Fis, act additively to repress qrr2. Our data has uncovered a new mechanism of qrr expression and shows that Qrr2 sRNA is sufficient for OpaR regulation. Importance The quorum sensing non-coding sRNAs are present in all Vibrio species but vary in number and regulatory roles among species. In the Harveyi clade, all species contain five qrr genes, and in V. harveyi these are transcribed by sigma-54 and are additive in function. In the Cholerae clade, four qrr genes are present, and in V. cholerae the qrr genes are redundant in function. In V. parahaemolyticus, qrr2 is controlled by two overlapping promoters. In an rpoN mutant, qrr2 is transcribed from a sigma-70 promoter that is present in all V. parahaemolyticus strains and in other species of the Harveyi clade suggesting a conserved mechanism of regulation. Qrr2 sRNA can function as the sole Qrr sRNA to control OpaR.
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11
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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: 5] [Impact Index Per Article: 1.3] [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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12
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Tunable Transcriptional Interference at the Endogenous Alcohol Dehydrogenase Gene Locus in Drosophila melanogaster. G3-GENES GENOMES GENETICS 2020; 10:1575-1583. [PMID: 32213532 PMCID: PMC7202008 DOI: 10.1534/g3.119.400937] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Neighboring sequences of a gene can influence its expression. In the phenomenon known as transcriptional interference, transcription at one region in the genome can repress transcription at a nearby region in cis. Transcriptional interference occurs at a number of eukaryotic loci, including the alcohol dehydrogenase (Adh) gene in Drosophila melanogaster. Adh is regulated by two promoters, which are distinct in their developmental timing of activation. It has been shown using transgene insertion that when the promoter distal from the Adh start codon is deleted, transcription from the proximal promoter becomes de-regulated. As a result, the Adh proximal promoter, which is normally active only during the early larval stages, becomes abnormally activated in adults. Whether this type of regulation occurs in the endogenous Adh context, however, remains unclear. Here, we employed the CRISPR/Cas9 system to edit the endogenous Adh locus and found that removal of the distal promoter also resulted in the untimely expression of the proximal promoter-driven mRNA isoform in adults, albeit at lower levels than previously reported. Importantly, transcription from the distal promoter was sufficient to repress proximal transcription in larvae, and the degree of this repression was dependent on the degree of distal promoter activity. Finally, upregulation of the distal Adh transcript led to the enrichment of histone 3 lysine 36 trimethylation over the Adh proximal promoter. We conclude that the endogenous Adh locus is developmentally regulated by transcriptional interference in a tunable manner.
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13
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Retnoningrum DS, Santika IWM, Kesuma S, Ekowati SA, Riani C. Construction and Characterization of a Medium Copy Number Expression Vector Carrying Auto-Inducible dps Promoter to Overproduce a Bacterial Superoxide Dismutase in Escherichia coli. Mol Biotechnol 2019; 61:231-240. [PMID: 30721405 DOI: 10.1007/s12033-018-00151-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Medium copy number expression vector and auto-inducible promoter could be a solution for producing recombinant therapeutic proteins in industrial scale regarding plasmid stability, cost, and product quality. This work aimed to construct a medium copy number pBR322-based expression vector carrying auto-inducible promoter, determine its ability to express heterologous gene, and study its segregational stability. Three stationary-phase promoters of Escherichia coli genes (gadA, dps and sbmC) were used to produce a superoxide dismutase from Staphylococcus equorum (rMnSODSeq) coding region from pBR322Δtet (pBR322-mini). Four plasmids were constructed with different promoters, i.e., T7 (pBMsod), gadA (pMCDsod), dps (pCADsod), and sbmC (pCDSsod) using pBR322-mini as backbone. Results showed that rMnSODSeq expression from pBMsod was significantly higher than that from pJExpress414sod (high copy number plasmid). Meanwhile, rMnSODSeq from pCADsod (auto-inducible promoter) was as high as from pBMsod (IPTG-inducible T7 promoter). rMnSODSeq expressed from pCADsod when bacterial cells entered stationary phase appeared as an active protein band of 23.5 kDa when analyzed by zymography and SDS-PAGE. pCADsod displayed the highest stability compared with pBMsod and pJEXpress414sod by plasmid retention assay. We demonstrate the use of an auto-inducible dps promoter to express high level of heterologous protein, an SOD of S. equorum, from a stable expression vector with medium copy number.
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Affiliation(s)
- Debbie Soefie Retnoningrum
- Laboratory of Pharmaceutical Biotechnology, School of Pharmacy, Institut Teknologi Bandung, Bandung, 40132, Indonesia.
| | - I Wayan Martadi Santika
- Laboratory of Pharmaceutical Biotechnology, School of Pharmacy, Institut Teknologi Bandung, Bandung, 40132, Indonesia
| | - Suryanata Kesuma
- Laboratory of Pharmaceutical Biotechnology, School of Pharmacy, Institut Teknologi Bandung, Bandung, 40132, Indonesia
| | - Syahdu Ayu Ekowati
- Laboratory of Pharmaceutical Biotechnology, School of Pharmacy, Institut Teknologi Bandung, Bandung, 40132, Indonesia
| | - Catur Riani
- Laboratory of Pharmaceutical Biotechnology, School of Pharmacy, Institut Teknologi Bandung, Bandung, 40132, Indonesia
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14
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Stoian N, Kaganjo J, Zeilstra-Ryalls J. Resolving the roles of the Rhodobacter sphaeroides HemA and HemT 5-aminolevulinic acid synthases. Mol Microbiol 2018; 110:1011-1029. [PMID: 30232811 DOI: 10.1111/mmi.14133] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Revised: 09/12/2018] [Accepted: 09/14/2018] [Indexed: 11/30/2022]
Abstract
Strains of the phototrophic alpha-proteobacterium Rhodobacter sphaeroides vary in the number of enzymes catalyzing the formation of 5-aminolevulinic acid (ALA synthases) that are encoded in their genomes. All have hemA, but not all have hemT. This study compared transcription of these genes, and also properties of their products among three wild-type strains; 2.4.3 has hemA alone, 2.4.1 and 2.4.9 have both hemA and hemT. Using lacZ reporter plasmids all hemA genes were found to be upregulated under anaerobic conditions, but induction amplitudes differ. hemT is transcriptionally silent in 2.4.1 but actively transcribed in 2.4.9, and strongly upregulated under anaerobic-dark growth conditions when cells are respiring dimethyl sulfoxide, vs. aerobic-dark or phototrophic (anaerobic-light) conditions. Two extracytoplasmic function (ECF)-type sigma factors present in 2.4.9, but absent from 2.4.1 are directly involved in hemT transcription. Kinetic properties of the ALA synthases of all three strains were similar, but HemT enzymes are far less sensitive to feedback inhibition by hemin than HemA enzymes, and HemT is less active under oxidizing conditions. A model is presented that compares and contrast events in strains 2.4.1 and 2.4.9.
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Affiliation(s)
- Natalie Stoian
- Department of Biological Sciences, Bowling Green State University, Bowling Green, OH, USA
| | - James Kaganjo
- Department of Biological Sciences, Bowling Green State University, Bowling Green, OH, USA
| | - Jill Zeilstra-Ryalls
- Department of Biological Sciences, Bowling Green State University, Bowling Green, OH, USA
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15
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Prasse D, Schmitz RA. Small RNAs Involved in Regulation of Nitrogen Metabolism. Microbiol Spectr 2018; 6:10.1128/microbiolspec.rwr-0018-2018. [PMID: 30027888 PMCID: PMC11633612 DOI: 10.1128/microbiolspec.rwr-0018-2018] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Indexed: 02/08/2023] Open
Abstract
Global (metabolic) regulatory networks allow microorganisms to survive periods of nitrogen starvation or general nutrient stress. Uptake and utilization of various nitrogen sources are thus commonly tightly regulated in Prokarya (Bacteria and Archaea) in response to available nitrogen sources. Those well-studied regulations occur mainly at the transcriptional and posttranslational level. Surprisingly, and in contrast to their involvement in most other stress responses, small RNAs (sRNAs) involved in the response to environmental nitrogen fluctuations are only rarely reported. In addition to sRNAs indirectly affecting nitrogen metabolism, only recently it was demonstrated that three sRNAs were directly involved in regulation of nitrogen metabolism in response to changes in available nitrogen sources. All three trans-acting sRNAs are under direct transcriptional control of global nitrogen regulators and affect expression of components of nitrogen metabolism (glutamine synthetase, nitrogenase, and PII-like proteins) by either masking the ribosome binding site and thus inhibiting translation initiation or stabilizing the respective target mRNAs. Most likely, there are many more sRNAs and other types of noncoding RNAs, e.g., riboswitches, involved in the regulation of nitrogen metabolism in Prokarya that remain to be uncovered. The present review summarizes the current knowledge on sRNAs involved in nitrogen metabolism and their biological functions and targets.
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Affiliation(s)
- Daniela Prasse
- Christian-Albrechts-University Kiel, Institute of General Microbiology, D-24118 Kiel, Germany
| | - Ruth A Schmitz
- Christian-Albrechts-University Kiel, Institute of General Microbiology, D-24118 Kiel, Germany
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16
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The fight for invincibility: Environmental stress response mechanisms and Aeromonas hydrophila. Microb Pathog 2018; 116:135-145. [PMID: 29355702 DOI: 10.1016/j.micpath.2018.01.023] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2017] [Revised: 01/15/2018] [Accepted: 01/15/2018] [Indexed: 12/11/2022]
Abstract
Aeromonas hydrophila is a freshwater-dwelling zoonotic bacterium that has economic importance in aquaculture. In the past decade, Aeromonas hydrophila has become increasingly important because of its emergence as a food-borne zoonotic pathogen that is resistant to different treatment regimes. Being an aquatic bacterium, Aeromonas hydrophila is frequently subjected to several stressful environmental conditions, including changes in temperature, acidic pH and starvation that challenge its survival. To cope with these stressful conditions, like every cell, A. hydrophila possesses stress response mechanisms, such as alternative sigma factors, two-component systems, heat shock proteins, cold shock proteins, and acid tolerance response systems that eventually lead the fittest to survive. Moreover, the establishment of genetic variations among the strains related to environmental stress is also of great concern. This review presents the understandings based on inter-strain variations and stress response behavior of A. hydrophila that are important to control the increasing outbreaks of this bacterium in both human populations and aquaculture.
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17
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Genome-Wide Transcriptional Response to Varying RpoS Levels in Escherichia coli K-12. J Bacteriol 2017; 199:JB.00755-16. [PMID: 28115545 DOI: 10.1128/jb.00755-16] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Accepted: 01/12/2017] [Indexed: 01/31/2023] Open
Abstract
The alternative sigma factor RpoS is a central regulator of many stress responses in Escherichia coli The level of functional RpoS differs depending on the stress. The effect of these differing concentrations of RpoS on global transcriptional responses remains unclear. We investigated the effect of RpoS concentration on the transcriptome during stationary phase in rich media. We found that 23% of genes in the E. coli genome are regulated by RpoS, and we identified many RpoS-transcribed genes and promoters. We observed three distinct classes of response to RpoS by genes in the regulon: genes whose expression changes linearly with increasing RpoS level, genes whose expression changes dramatically with the production of only a little RpoS ("sensitive" genes), and genes whose expression changes very little with the production of a little RpoS ("insensitive"). We show that sequences outside the core promoter region determine whether an RpoS-regulated gene is sensitive or insensitive. Moreover, we show that sensitive and insensitive genes are enriched for specific functional classes and that the sensitivity of a gene to RpoS corresponds to the timing of induction as cells enter stationary phase. Thus, promoter sensitivity to RpoS is a mechanism to coordinate specific cellular processes with growth phase and may also contribute to the diversity of stress responses directed by RpoS.IMPORTANCE The sigma factor RpoS is a global regulator that controls the response to many stresses in Escherichia coli Different stresses result in different levels of RpoS production, but the consequences of this variation are unknown. We describe how changing the level of RpoS does not influence all RpoS-regulated genes equally. The cause of this variation is likely the action of transcription factors that bind the promoters of the genes. We show that the sensitivity of a gene to RpoS levels explains the timing of expression as cells enter stationary phase and that genes with different RpoS sensitivities are enriched for specific functional groups. Thus, promoter sensitivity to RpoS is a mechanism that coordinates specific cellular processes in response to stresses.
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18
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Cavaliere P, Norel F. Recent advances in the characterization of Crl, the unconventional activator of the stress sigma factor σS/RpoS. Biomol Concepts 2017; 7:197-204. [PMID: 27180360 DOI: 10.1515/bmc-2016-0006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 03/29/2016] [Indexed: 11/15/2022] Open
Abstract
The bacterial RNA polymerase (RNAP) holoenzyme is a multisubunit core enzyme associated with a σ factor that is required for promoter-specific transcription initiation. Besides a primary σ responsible for most of the gene expression during active growth, bacteria contain alternative σ factors that control adaptive responses. A recurring strategy in the control of σ factor activity is their sequestration by anti-sigma factors that occlude the RNAP binding determinants, reducing their activity. In contrast, the unconventional transcription factor Crl binds specifically to the alternative σ factor σS/RpoS, and favors its association with the core RNAP, thereby increasing its activity. σS is the master regulator of the general stress response that protects many Gram-negative bacteria from several harmful environmental conditions. It is also required for biofilm formation and virulence of Salmonella enterica serovar Typhimurium. In this report, we discuss current knowledge on the regulation and function of Crl in Salmonella and Escherichia coli, two bacterial species in which Crl has been studied. We review recent advances in the structural characterization of the Crl-σS interaction that have led to a better understanding of this unusual mechanism of σ regulation.
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19
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Sanchuki HBS, Gravina F, Rodrigues TE, Gerhardt ECM, Pedrosa FO, Souza EM, Raittz RT, Valdameri G, de Souza GA, Huergo LF. Dynamics of the Escherichia coli proteome in response to nitrogen starvation and entry into the stationary phase. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2016; 1865:344-352. [PMID: 27939605 DOI: 10.1016/j.bbapap.2016.12.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Revised: 12/02/2016] [Accepted: 12/06/2016] [Indexed: 01/31/2023]
Abstract
Nitrogen is needed for the biosynthesis of biomolecules including proteins and nucleic acids. In the absence of fixed nitrogen prokaryotes such as E. coli immediately ceases growth. Ammonium is the preferred nitrogen source for E. coli supporting the fastest growth rates. Under conditions of ammonium limitation, E. coli can use alternative nitrogen sources to supply ammonium ions and this reprogramming is led by the induction of the NtrC regulon. Here we used label free proteomics to determine the dynamics of E. coli proteins expression in response to ammonium starvation in both the short (30min) and the longer (60min) starvation. Protein abundances and post-translational modifications confirmed that activation of the NtrC regulon acts as the first line of defense against nitrogen starvation. The ribosome inactivating protein Rmf was induced shortly after ammonium exhaustion and this was preceded by induction of other ribosome inactivating proteins such as Hpf and RaiA supporting the hypothesis that ribosome shut-down is a key process during nitrogen limitation stress. The proteomic data revealed that growth arrest due to nitrogen starvation correlates with the accumulation of proteins involved in DNA condensation, RNA and protein catabolism and ribosome hibernation. Collectively, these proteome adaptations will result in metabolic inactive cells which are likely to exhibit multidrug tolerance.
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Affiliation(s)
| | - Fernanda Gravina
- Departamento de Bioquímica e Biologia Molecular, UFPR, Curitiba, PR, Brazil
| | - Thiago E Rodrigues
- Departamento de Bioquímica e Biologia Molecular, UFPR, Curitiba, PR, Brazil
| | | | - Fábio O Pedrosa
- Departamento de Bioquímica e Biologia Molecular, UFPR, Curitiba, PR, Brazil
| | - Emanuel M Souza
- Departamento de Bioquímica e Biologia Molecular, UFPR, Curitiba, PR, Brazil
| | - Roberto T Raittz
- Setor de Educação Profissional e Tecnológica, UFPR, Curitiba, PR, Brazil
| | - Glaucio Valdameri
- Departamento de Bioquímica e Biologia Molecular, UFPR, Curitiba, PR, Brazil; Departamento de Análises Clínicas, UFPR, Curitiba, PR, Brazil
| | - Gustavo A de Souza
- Department of Immunology, University of Oslo and Oslo University Hospital, The Proteomics Core Facility, Rikshospitalet, Oslo, Norway; Instituto do Cérebro, UFRN, Natal, RN, Brazil
| | - Luciano F Huergo
- Departamento de Bioquímica e Biologia Molecular, UFPR, Curitiba, PR, Brazil; Setor Litoral, UFPR, Matinhos, PR, Brazil.
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20
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Grabowicz M, Silhavy TJ. Envelope Stress Responses: An Interconnected Safety Net. Trends Biochem Sci 2016; 42:232-242. [PMID: 27839654 DOI: 10.1016/j.tibs.2016.10.002] [Citation(s) in RCA: 102] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Revised: 10/12/2016] [Accepted: 10/17/2016] [Indexed: 12/14/2022]
Abstract
The Escherichia coli cell envelope is a protective barrier at the frontline of interaction with the environment. Fidelity of envelope biogenesis must be monitored to establish and maintain a contiguous barrier. Indeed, the envelope must also be repaired and modified in response to environmental assaults. Envelope stress responses (ESRs) sense envelope damage or defects and alter the transcriptome to mitigate stress. Here, we review recent insights into the stress-sensing mechanisms of the σE and Cpx systems and the interaction of these ESRs. Small RNAs (sRNAs) are increasingly prominent regulators of the transcriptional response to stress. These fast-acting regulators also provide avenues for inter-ESR regulation that could be important when cells face multiple contemporaneous stresses, as is the case during infection.
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Affiliation(s)
- Marcin Grabowicz
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Thomas J Silhavy
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA.
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21
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Ard R, Allshire RC. Transcription-coupled changes to chromatin underpin gene silencing by transcriptional interference. Nucleic Acids Res 2016; 44:10619-10630. [PMID: 27613421 PMCID: PMC5159543 DOI: 10.1093/nar/gkw801] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Revised: 08/17/2016] [Accepted: 08/31/2016] [Indexed: 02/07/2023] Open
Abstract
Long non-coding RNA (lncRNA) transcription into a downstream promoter frequently results in transcriptional interference. However, the mechanism of this repression is not fully understood. We recently showed that drug tolerance in fission yeast Schizosaccharomyces pombe is controlled by lncRNA transcription upstream of the tgp1+ permease gene. Here we demonstrate that transcriptional interference of tgp1+ involves several transcription-coupled chromatin changes mediated by conserved elongation factors Set2, Clr6CII, Spt6 and FACT. These factors are known to travel with RNAPII and establish repressive chromatin in order to limit aberrant transcription initiation from cryptic promoters present in gene bodies. We therefore conclude that conserved RNAPII-associated mechanisms exist to both suppress intragenic cryptic promoters during genic transcription and to repress gene promoters by transcriptional interference. Our analyses also demonstrate that key mechanistic features of transcriptional interference are shared between S. pombe and the highly divergent budding yeast Saccharomyces cerevisiae. Thus, transcriptional interference is an ancient, conserved mechanism for tightly controlling gene expression. Our mechanistic insights allowed us to predict and validate a second example of transcriptional interference involving the S. pombe pho1+ gene. Given that eukaryotic genomes are pervasively transcribed, transcriptional interference likely represents a more general feature of gene regulation than is currently appreciated.
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Affiliation(s)
- Ryan Ard
- Wellcome Trust Centre for Cell Biology and Institute of Cell Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh EH9 3BF, Scotland, UK
| | - Robin C Allshire
- Wellcome Trust Centre for Cell Biology and Institute of Cell Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh EH9 3BF, Scotland, UK
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22
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Hao Y, Updegrove TB, Livingston NN, Storz G. Protection against deleterious nitrogen compounds: role of σS-dependent small RNAs encoded adjacent to sdiA. Nucleic Acids Res 2016; 44:6935-48. [PMID: 27166377 PMCID: PMC5001591 DOI: 10.1093/nar/gkw404] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Accepted: 05/02/2016] [Indexed: 11/16/2022] Open
Abstract
Here, we report the characterization of a set of small, regulatory RNAs (sRNAs) expressed from an Escherichia coli locus we have denoted sdsN located adjacent to the LuxR-homolog gene sdiA. Two longer sRNAs, SdsN137 and SdsN178 are transcribed from two σS-dependent promoters but share the same terminator. Low temperature, rich nitrogen sources and the Crl and NarP transcription factors differentially affect the levels of the SdsN transcripts. Whole genome expression analysis after pulse overexpression of SdsN137 and assays of lacZ fusions revealed that the SdsN137 directly represses the synthesis of the nitroreductase NfsA, which catalyzes the reduction of the nitrogroup (NO2) in nitroaromatic compounds and the flavohemoglobin HmpA, which has aerobic nitric oxide (NO) dioxygenase activity. Consistent with this regulation, SdsN137 confers resistance to nitrofurans. In addition, SdsN137 negatively regulates synthesis of NarP. Interestingly, SdsN178 is defective at regulating the above targets due to unusual binding to the Hfq protein, but cleavage leads to a shorter form, SdsN124, able to repress nfsA and hmpA.
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Affiliation(s)
- Yue Hao
- Division of Molecular and Cellular Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892-5430, USA
| | - Taylor B Updegrove
- Division of Molecular and Cellular Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892-5430, USA
| | - Natasha N Livingston
- Division of Molecular and Cellular Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892-5430, USA
| | - Gisela Storz
- Division of Molecular and Cellular Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892-5430, USA
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23
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Abstract
The metabolite 2-oxoglutarate (also known as α-ketoglutarate, 2-ketoglutaric acid, or oxoglutaric acid) lies at the intersection between the carbon and nitrogen metabolic pathways. This compound is a key intermediate of one of the most fundamental biochemical pathways in carbon metabolism, the tricarboxylic acid (TCA) cycle. In addition, 2-oxoglutarate also acts as the major carbon skeleton for nitrogen-assimilatory reactions. Experimental data support the conclusion that intracellular levels of 2-oxoglutarate fluctuate according to nitrogen and carbon availability. This review summarizes how nature has capitalized on the ability of 2-oxoglutarate to reflect cellular nutritional status through evolution of a variety of 2-oxoglutarate-sensing regulatory proteins. The number of metabolic pathways known to be regulated by 2-oxoglutarate levels has increased significantly in recent years. The signaling properties of 2-oxoglutarate are highlighted by the fact that this metabolite regulates the synthesis of the well-established master signaling molecule, cyclic AMP (cAMP), in Escherichia coli.
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24
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Moreau PL, Loiseau L. Characterization of acetic acid-detoxifying Escherichia coli evolved under phosphate starvation conditions. Microb Cell Fact 2016; 15:42. [PMID: 26895825 PMCID: PMC4759930 DOI: 10.1186/s12934-016-0441-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Accepted: 02/07/2016] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND During prolonged incubation of Escherichia coli K-12 in batch culture under aerobic, phosphate (Pi) starvation conditions, excess glucose is converted into acetic acid, which may trigger cell death. Following serial cultures, we isolated five evolved strains in two populations that survived prolonged incubation. METHODS We sequenced the genomes of the ancestral and evolved strains, and determined the effects of the genetic changes, tested alone and in combination, on characteristic phenotypes in pure and in mixed cultures. RESULTS Evolved strains used two main strategies: (1) the constitutive expression of the Trk- and Kdp-dependent K(+) transport systems, and (2) the inactivation of the ArcA global regulator. Both processes helped to maintain a residual activity of the tricarboxylic acid cycle, which decreased the production of acetic acid and eventually allowed its re-consumption. Evolved strains acquired a few additional genetic changes besides the trkH, kdpD and arcA mutations, which might increase the scavenging of organophosphates (phnE (+), lapB, and rseP) and the resistance to oxidative (rsxC) and acetic acid stresses (e14(-)/icd (+)). CONCLUSIONS Evolved strains rapidly acquired mutations (phnE (+) lapB rpoS trkH and phnE (+) rseP kdpD) that were globally beneficial to growth on glucose and organophosphates, but detrimental to long-term viability. The spread of these mutant strains might give the ancestral strain time to accumulate up to five genetic changes (phnE (+) arcA rsxC crfC e14(-)/icd (+)), which allowed growth on glucose and organophosphates, and provided a long-term survival. The latter strain, which expressed several mechanisms of protection against endogenous and exogenous stresses, might provide a platform for producing toxic recombinant proteins and chemicals during prolonged incubation under aerobic, Pi starvation conditions.
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Affiliation(s)
- Patrice L Moreau
- Laboratoire de Chimie Bactérienne, UMR 7283, Aix-Marseille Université, Marseille, France.
- Institut de Microbiologie de la Méditerranée, Centre National de la Recherche Scientifique, Marseille, France.
| | - Laurent Loiseau
- Laboratoire de Chimie Bactérienne, UMR 7283, Aix-Marseille Université, Marseille, France.
- Institut de Microbiologie de la Méditerranée, Centre National de la Recherche Scientifique, Marseille, France.
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25
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Bonocora RP, Smith C, Lapierre P, Wade JT. Genome-Scale Mapping of Escherichia coli σ54 Reveals Widespread, Conserved Intragenic Binding. PLoS Genet 2015; 11:e1005552. [PMID: 26425847 PMCID: PMC4591121 DOI: 10.1371/journal.pgen.1005552] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Accepted: 09/03/2015] [Indexed: 11/18/2022] Open
Abstract
Bacterial RNA polymerases must associate with a σ factor to bind promoter DNA and initiate transcription. There are two families of σ factor: the σ70 family and the σ54 family. Members of the σ54 family are distinct in their ability to bind promoter DNA sequences, in the context of RNA polymerase holoenzyme, in a transcriptionally inactive state. Here, we map the genome-wide association of Escherichia coli σ54, the archetypal member of the σ54 family. Thus, we vastly expand the list of known σ54 binding sites to 135. Moreover, we estimate that there are more than 250 σ54 sites in total. Strikingly, the majority of σ54 binding sites are located inside genes. The location and orientation of intragenic σ54 binding sites is non-random, and many intragenic σ54 binding sites are conserved. We conclude that many intragenic σ54 binding sites are likely to be functional. Consistent with this assertion, we identify three conserved, intragenic σ54 promoters that drive transcription of mRNAs with unusually long 5ʹ UTRs. Bacterial RNA polymerases must associate with a σ factor to bind to promoter DNA sequences upstream of genes and initiate transcription. There are two families of σ factor: σ70 and σ54. Members of the σ54 family are distinct from members of the σ70 family in their ability to bind promoter DNA sequences, in association with RNA polymerase, in a transcriptionally inactive state. We have determined positions in the Escherichia coli genome that are bound by σ54, the archetypal member of the σ54 family. Surprisingly, we identified 135 binding sites for σ54, a huge increase over the number of previously described sites. Our data suggest that there are more than 250 σ54 sites in total. Strikingly, most σ54 binding sites are located inside genes, whereas only one intragenic σ54 binding site has previously been described. The location and orientation of intragenic σ54 binding sites is non-random, and many intragenic σ54 binding sites are conserved in other bacterial species. We conclude that many intragenic σ54 binding sites are likely to be functional. Consistent with this notion, we identify three σ54 promoters in E. coli that are located inside genes but drive transcription of unusual mRNAs for the neighboring genes.
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Affiliation(s)
- Richard P. Bonocora
- Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
| | - Carol Smith
- Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
| | - Pascal Lapierre
- Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
| | - Joseph T. Wade
- Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
- Department of Biomedical Sciences, School of Public Health, University at Albany, Albany, New York, United States of America
- * E-mail:
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26
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Schaefer J, Engl C, Zhang N, Lawton E, Buck M. Genome wide interactions of wild-type and activator bypass forms of σ54. Nucleic Acids Res 2015; 43:7280-91. [PMID: 26082500 PMCID: PMC4551910 DOI: 10.1093/nar/gkv597] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Accepted: 05/25/2015] [Indexed: 01/05/2023] Open
Abstract
Enhancer-dependent transcription involving the promoter specificity factor σ54 is widely distributed amongst bacteria and commonly associated with cell envelope function. For transcription initiation, σ54-RNA polymerase yields open promoter complexes through its remodelling by cognate AAA+ ATPase activators. Since activators can be bypassed in vitro, bypass transcription in vivo could be a source of emergent gene expression along evolutionary pathways yielding new control networks and transcription patterns. At a single test promoter in vivo bypass transcription was not observed. We now use genome-wide transcription profiling, genome-wide mutagenesis and gene over-expression strategies in Escherichia coli, to (i) scope the range of bypass transcription in vivo and (ii) identify genes which might alter bypass transcription in vivo. We find little evidence for pervasive bypass transcription in vivo with only a small subset of σ54 promoters functioning without activators. Results also suggest no one gene limits bypass transcription in vivo, arguing bypass transcription is strongly kept in check. Promoter sequences subject to repression by σ54 were evident, indicating loss of rpoN (encoding σ54) rather than creating rpoN bypass alleles would be one evolutionary route for new gene expression patterns. Finally, cold-shock promoters showed unusual σ54-dependence in vivo not readily correlated with conventional σ54 binding-sites.
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Affiliation(s)
- Jorrit Schaefer
- Faculty of Natural Sciences, Division of Cell & Molecular Biology, Imperial College London, London SW7 2AZ, UK
| | - Christoph Engl
- Faculty of Natural Sciences, Division of Cell & Molecular Biology, Imperial College London, London SW7 2AZ, UK Institute for Global Food Security, Queen's University Belfast, Belfast BT9 5BN, UK
| | - Nan Zhang
- Faculty of Natural Sciences, Division of Cell & Molecular Biology, Imperial College London, London SW7 2AZ, UK
| | - Edward Lawton
- Faculty of Natural Sciences, Division of Cell & Molecular Biology, Imperial College London, London SW7 2AZ, UK
| | - Martin Buck
- Faculty of Natural Sciences, Division of Cell & Molecular Biology, Imperial College London, London SW7 2AZ, UK
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27
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Phaiboun A, Zhang Y, Park B, Kim M. Survival kinetics of starving bacteria is biphasic and density-dependent. PLoS Comput Biol 2015; 11:e1004198. [PMID: 25838110 PMCID: PMC4383377 DOI: 10.1371/journal.pcbi.1004198] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 02/16/2015] [Indexed: 11/19/2022] Open
Abstract
In the lifecycle of microorganisms, prolonged starvation is prevalent and sustaining life during starvation periods is a vital task. In the literature, it is commonly assumed that survival kinetics of starving microbes follows exponential decay. This assumption, however, has not been rigorously tested. Currently, it is not clear under what circumstances this assumption is true. Also, it is not known when such survival kinetics deviates from exponential decay and if it deviates, what underlying mechanisms for the deviation are. Here, to address these issues, we quantitatively characterized dynamics of survival and death of starving E. coli cells. The results show that the assumption--starving cells die exponentially--is true only at high cell density. At low density, starving cells persevere for extended periods of time, before dying rapidly exponentially. Detailed analyses show intriguing quantitative characteristics of the density-dependent and biphasic survival kinetics, including that the period of the perseverance is inversely proportional to cell density. These characteristics further lead us to identification of key underlying processes relevant for the perseverance of starving cells. Then, using mathematical modeling, we show how these processes contribute to the density-dependent and biphasic survival kinetics observed. Importantly, our model reveals a thrifty strategy employed by bacteria, by which upon sensing impending depletion of a substrate, the limiting substrate is conserved and utilized later during starvation to delay cell death. These findings advance quantitative understanding of survival of microbes in oligotrophic environments and facilitate quantitative analysis and prediction of microbial dynamics in nature. Furthermore, they prompt revision of previous models used to analyze and predict population dynamics of microbes.
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Affiliation(s)
- Andy Phaiboun
- Department of Physics, Emory University, Atlanta, Georgia, United States of America
| | - Yiming Zhang
- Department of Physics, Emory University, Atlanta, Georgia, United States of America
| | - Boryung Park
- Department of Physics, Emory University, Atlanta, Georgia, United States of America
| | - Minsu Kim
- Department of Physics, Emory University, Atlanta, Georgia, United States of America
- Graduate Division of Biological and Biomedical Sciences, Emory University, Atlanta, Georgia, United States of America
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28
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Lévi-Meyrueis C, Monteil V, Sismeiro O, Dillies MA, Kolb A, Monot M, Dupuy B, Duarte SS, Jagla B, Coppée JY, Beraud M, Norel F. Repressor activity of the RpoS/σS-dependent RNA polymerase requires DNA binding. Nucleic Acids Res 2015; 43:1456-68. [PMID: 25578965 PMCID: PMC4330354 DOI: 10.1093/nar/gku1379] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The RpoS/σ(S) sigma subunit of RNA polymerase (RNAP) activates transcription of stationary phase genes in many Gram-negative bacteria and controls adaptive functions, including stress resistance, biofilm formation and virulence. In this study, we address an important but poorly understood aspect of σ(S)-dependent control, that of a repressor. Negative regulation by σ(S) has been proposed to result largely from competition between σ(S) and other σ factors for binding to a limited amount of core RNAP (E). To assess whether σ(S) binding to E alone results in significant downregulation of gene expression by other σ factors, we characterized an rpoS mutant of Salmonella enterica serovar Typhimurium producing a σ(S) protein proficient for Eσ(S) complex formation but deficient in promoter DNA binding. Genome expression profiling and physiological assays revealed that this mutant was defective for negative regulation, indicating that gene repression by σ(S) requires its binding to DNA. Although the mechanisms of repression by σ(S) are likely specific to individual genes and environmental conditions, the study of transcription downregulation of the succinate dehydrogenase operon suggests that σ competition at the promoter DNA level plays an important role in gene repression by Eσ(S).
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Affiliation(s)
- Corinne Lévi-Meyrueis
- Institut Pasteur, Laboratoire Systèmes Macromoléculaires et Signalisation, Département de Microbiologie, rue du Docteur Roux, 75015 Paris, France CNRS ERL3526, rue du Docteur Roux, 75015 Paris, France Université Paris Sud XI, 15, rue Georges Clémenceau, 91405 Orsay Cedex, France
| | - Véronique Monteil
- Institut Pasteur, Laboratoire Systèmes Macromoléculaires et Signalisation, Département de Microbiologie, rue du Docteur Roux, 75015 Paris, France CNRS ERL3526, rue du Docteur Roux, 75015 Paris, France
| | - Odile Sismeiro
- Institut Pasteur, Plate-forme Transcriptome et Epigénome, Département Génomes et génétique, rue du Docteur Roux, 75015 Paris, France
| | - Marie-Agnès Dillies
- Institut Pasteur, Plate-forme Transcriptome et Epigénome, Département Génomes et génétique, rue du Docteur Roux, 75015 Paris, France
| | - Annie Kolb
- Institut Pasteur, Laboratoire Systèmes Macromoléculaires et Signalisation, Département de Microbiologie, rue du Docteur Roux, 75015 Paris, France CNRS ERL3526, rue du Docteur Roux, 75015 Paris, France
| | - Marc Monot
- Institut Pasteur, Laboratoire Pathogenèse des bactéries anaérobies, Département de Microbiologie, rue du Docteur Roux, 75015 Paris, France
| | - Bruno Dupuy
- Institut Pasteur, Laboratoire Pathogenèse des bactéries anaérobies, Département de Microbiologie, rue du Docteur Roux, 75015 Paris, France
| | - Sara Serradas Duarte
- Institut Pasteur, Laboratoire Systèmes Macromoléculaires et Signalisation, Département de Microbiologie, rue du Docteur Roux, 75015 Paris, France CNRS ERL3526, rue du Docteur Roux, 75015 Paris, France
| | - Bernd Jagla
- Institut Pasteur, Plate-forme Transcriptome et Epigénome, Département Génomes et génétique, rue du Docteur Roux, 75015 Paris, France
| | - Jean-Yves Coppée
- Institut Pasteur, Plate-forme Transcriptome et Epigénome, Département Génomes et génétique, rue du Docteur Roux, 75015 Paris, France
| | - Mélanie Beraud
- Institut Pasteur, Laboratoire Systèmes Macromoléculaires et Signalisation, Département de Microbiologie, rue du Docteur Roux, 75015 Paris, France CNRS ERL3526, rue du Docteur Roux, 75015 Paris, France Université Paris Diderot, Sorbonne Paris Cité, Cellule Pasteur, Paris, rue du Docteur Roux, 75015 Paris, France
| | - Françoise Norel
- Institut Pasteur, Laboratoire Systèmes Macromoléculaires et Signalisation, Département de Microbiologie, rue du Docteur Roux, 75015 Paris, France CNRS ERL3526, rue du Docteur Roux, 75015 Paris, France
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29
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Ard R, Tong P, Allshire RC. Long non-coding RNA-mediated transcriptional interference of a permease gene confers drug tolerance in fission yeast. Nat Commun 2014; 5:5576. [PMID: 25428589 PMCID: PMC4255232 DOI: 10.1038/ncomms6576] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Accepted: 10/15/2014] [Indexed: 11/09/2022] Open
Abstract
Most long non-coding RNAs (lncRNAs) encoded by eukaryotic genomes remain uncharacterized. Here we focus on a set of intergenic lncRNAs in fission yeast. Deleting one of these lncRNAs exhibited a clear phenotype: drug sensitivity. Detailed analyses of the affected locus revealed that transcription of the nc-tgp1 lncRNA regulates drug tolerance by repressing the adjacent phosphate-responsive permease gene transporter for glycerophosphodiester 1 (tgp1+). We demonstrate that the act of transcribing nc-tgp1 over the tgp1+ promoter increases nucleosome density, prevents transcription factor access and thus represses tgp1+ without the need for RNA interference or heterochromatin components. We therefore conclude that tgp1+ is regulated by transcriptional interference. Accordingly, decreased nc-tgp1 transcription permits tgp1+ expression upon phosphate starvation. Furthermore, nc-tgp1 loss induces tgp1+ even in repressive conditions. Notably, drug sensitivity results directly from tgp1+ expression in the absence of the nc-tgp1 RNA. Thus, transcription of an lncRNA governs drug tolerance in fission yeast. The presence of long non-coding RNAs (lncRNAs) is pervasive across genomes, yet few lncRNAs have clearly established mechanisms of action. Here the authors demonstrate that the fission yeast lncRNA nc-tgp1 regulates expression of the drug tolerance gene tgp1+ via+ transcriptional interference.
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Affiliation(s)
- Ryan Ard
- Wellcome Trust Centre for Cell Biology and Institute of Cell Biology, School of Biological Sciences, The University of Edinburgh, Max Born Crescent, Edinburgh EH9 3BF, Scotland, UK
| | - Pin Tong
- Wellcome Trust Centre for Cell Biology and Institute of Cell Biology, School of Biological Sciences, The University of Edinburgh, Max Born Crescent, Edinburgh EH9 3BF, Scotland, UK
| | - Robin C Allshire
- Wellcome Trust Centre for Cell Biology and Institute of Cell Biology, School of Biological Sciences, The University of Edinburgh, Max Born Crescent, Edinburgh EH9 3BF, Scotland, UK
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30
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The PqsR and RhlR transcriptional regulators determine the level of Pseudomonas quinolone signal synthesis in Pseudomonas aeruginosa by producing two different pqsABCDE mRNA isoforms. J Bacteriol 2014; 196:4163-71. [PMID: 25225275 DOI: 10.1128/jb.02000-14] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Regulation of gene expression plays a key role in bacterial adaptability to changes in the environment. An integral part of this gene regulatory network is achieved via quorum sensing (QS) systems that coordinate bacterial responses under high cellular densities. In the nosocomial pathogen Pseudomonas aeruginosa, the 2-alkyl-4-quinolone (pqs) signaling pathway is crucial for bacterial survival under stressful conditions. Biosynthesis of the Pseudomonas quinolone signal (PQS) is dependent on the pqsABCDE operon, which is positively regulated by the LysR family regulator PqsR and repressed by the transcriptional regulator protein RhlR. However, the molecular mechanisms underlying this inhibition have remained elusive. Here, we demonstrate that not only PqsR but also RhlR activates transcription of pqsA. The latter uses an alternative transcriptional start site and induces expression of a longer transcript that forms a secondary structure in the 5' untranslated leader region. As a consequence, access of the ribosome to the Shine-Dalgarno sequence is restricted and translation efficiency reduced. We propose a model of a novel posttranscriptional regulation mechanism that fine-tunes PQS biosynthesis, thus highlighting the complexity of quorum sensing in P. aeruginosa.
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31
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Moreau PL. Protective role of the RpoE (σE) and Cpx envelope stress responses against gentamicin killing of nongrowing Escherichia coli incubated under aerobic, phosphate starvation conditions. FEMS Microbiol Lett 2014; 357:151-6. [PMID: 25039943 DOI: 10.1111/1574-6968.12534] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2014] [Revised: 06/28/2014] [Accepted: 07/04/2014] [Indexed: 11/29/2022] Open
Abstract
The viability of Escherichia coli starved of nitrogen (N) or phosphorus (P) decreased by up to seven orders of magnitude during prolonged incubation under aerobic conditions when exposed to high levels of the antibiotic gentamicin, whereas viability of cells starved of carbon (C) was barely affected. However, the initial rate of killing was lower for P-starved cells than for N-starved cells. The transient resistance of P-starved cells was partially dependent upon the expression of the phosphate (Pho) and Cpx responses. Constitutive activity of the Cpx and RpoE (σ(E)) envelope stress regulons increased the resistance of P- and N-starved cells. The level of expression of the RpoE regulon was fourfold higher in P-starved cells than in N-starved cell at the time gentamicin was added. Gentamicin killing of nongrowing cells may thus require ongoing aerobic glucose metabolism and faulty synthesis of structural membrane proteins. However, membrane protein damage induced by gentamicin can be eliminated or repaired by RpoE- and Cpx-dependent mechanisms pre-emptively induced in P-starved cells, which reveals a novel mechanism of resistance to gentamicin that is active in certain circumstances.
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Affiliation(s)
- Patrice L Moreau
- Laboratoire de Chimie Bactérienne, Centre National de la Recherche Scientifique, Aix-Marseille Université, Marseille, France
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32
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Structure of the RNA polymerase assembly factor Crl and identification of its interaction surface with sigma S. J Bacteriol 2014; 196:3279-88. [PMID: 25002538 DOI: 10.1128/jb.01910-14] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacteria utilize multiple sigma factors that associate with core RNA polymerase (RNAP) to control transcription in response to changes in environmental conditions. In Escherichia coli and Salmonella enterica, Crl positively regulates the σ(S) regulon by binding to σ(S) to promote its association with core RNAP. We recently characterized the determinants in σ(S) responsible for specific binding to Crl. However, little is known about the determinants in Crl required for this interaction. Here, we present the X-ray crystal structure of a Crl homolog from Proteus mirabilis in conjunction with in vivo and in vitro approaches that probe the Crl-σ(S) interaction in E. coli. We show that the P. mirabilis, Vibrio harveyi, and E. coli Crl homologs function similarly in E. coli, indicating that Crl structure and function are likely conserved throughout gammaproteobacteria. We utilize phylogenetic conservation and bacterial two-hybrid analyses to predict residues in Crl important for the interaction with σ(S). The results of p-benzoylphenylalanine (BPA)-mediated UV cross-linking studies further support the model in which an evolutionarily conserved central cleft is the surface on Crl that binds to σ(S). Within this conserved binding surface, we identify a key residue in Crl that is critical for activation of Eσ(S)-dependent transcription in vivo and in vitro. Our study provides a physical basis for understanding the σ(S)-Crl interaction.
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