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Baglivo I, Malgieri G, Roop RM, Barton IS, Wang X, Russo V, Pirone L, Pedone EM, Pedone PV. MucR protein: Three decades of studies have led to the identification of a new H-NS-like protein. Mol Microbiol 2024. [PMID: 38619026 DOI: 10.1111/mmi.15261] [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: 01/29/2024] [Revised: 03/22/2024] [Accepted: 03/25/2024] [Indexed: 04/16/2024]
Abstract
MucR belongs to a large protein family whose members regulate the expression of virulence and symbiosis genes in α-proteobacteria species. This protein and its homologs were initially studied as classical transcriptional regulators mostly involved in repression of target genes by binding their promoters. Very recent studies have led to the classification of MucR as a new type of Histone-like Nucleoid Structuring (H-NS) protein. Thus this review is an effort to put together a complete and unifying story demonstrating how genetic and biochemical findings on MucR suggested that this protein is not a classical transcriptional regulator, but functions as a novel type of H-NS-like protein, which binds AT-rich regions of genomic DNA and regulates gene expression.
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Affiliation(s)
- Ilaria Baglivo
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, University of Campania "Luigi Vanvitelli", Caserta, Italy
| | - Gaetano Malgieri
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, University of Campania "Luigi Vanvitelli", Caserta, Italy
| | - Roy Martin Roop
- Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, USA
| | - Ian S Barton
- Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, USA
| | - Xindan Wang
- Department of Biology, Indiana University, Bloomington, Indiana, USA
| | | | - Luciano Pirone
- Institute of Biostructures and Bioimaging, CNR, Naples, Italy
| | - Emilia M Pedone
- Institute of Biostructures and Bioimaging, CNR, Naples, Italy
| | - Paolo V Pedone
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, University of Campania "Luigi Vanvitelli", Caserta, Italy
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2
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Figueroa-Bossi N, Fernández-Fernández R, Kerboriou P, Bouloc P, Casadesús J, Sánchez-Romero MA, Bossi L. Transcription-driven DNA supercoiling counteracts H-NS-mediated gene silencing in bacterial chromatin. Nat Commun 2024; 15:2787. [PMID: 38555352 PMCID: PMC10981669 DOI: 10.1038/s41467-024-47114-w] [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: 10/09/2023] [Accepted: 03/19/2024] [Indexed: 04/02/2024] Open
Abstract
In all living cells, genomic DNA is compacted through interactions with dedicated proteins and/or the formation of plectonemic coils. In bacteria, DNA compaction is achieved dynamically, coordinated with dense and constantly changing transcriptional activity. H-NS, a major bacterial nucleoid structuring protein, is of special interest due to its interplay with RNA polymerase. H-NS:DNA nucleoprotein filaments inhibit transcription initiation by RNA polymerase. However, the discovery that genes silenced by H-NS can be activated by transcription originating from neighboring regions has suggested that elongating RNA polymerases can disassemble H-NS:DNA filaments. In this study, we present evidence that transcription-induced counter-silencing does not require transcription to reach the silenced gene; rather, it exerts its effect at a distance. Counter-silencing is suppressed by introducing a DNA gyrase binding site within the intervening segment, suggesting that the long-range effect results from transcription-driven positive DNA supercoils diffusing toward the silenced gene. We propose a model wherein H-NS:DNA complexes form in vivo on negatively supercoiled DNA, with H-NS bridging the two arms of the plectoneme. Rotational diffusion of positive supercoils generated by neighboring transcription will cause the H-NS-bound negatively-supercoiled plectoneme to "unroll" disrupting the H-NS bridges and releasing H-NS.
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Affiliation(s)
- Nara Figueroa-Bossi
- Université Paris-Saclay, CEA, CNRS, Institut de Biologie Intégrative de la Cellule (I2BC), Gif-sur-Yvette, France
| | - Rocío Fernández-Fernández
- Departamento de Microbiología y Parasitología, Facultad de Farmacia, Universidad de Sevilla, Sevilla, Spain
| | - Patricia Kerboriou
- Université Paris-Saclay, CEA, CNRS, Institut de Biologie Intégrative de la Cellule (I2BC), Gif-sur-Yvette, France
| | - Philippe Bouloc
- Université Paris-Saclay, CEA, CNRS, Institut de Biologie Intégrative de la Cellule (I2BC), Gif-sur-Yvette, France
| | - Josep Casadesús
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
| | | | - Lionello Bossi
- Université Paris-Saclay, CEA, CNRS, Institut de Biologie Intégrative de la Cellule (I2BC), Gif-sur-Yvette, France.
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3
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de Pedro-Jové R, Corral J, Rocafort M, Puigvert M, Azam FL, Vandecaveye A, Macho AP, Balsalobre C, Coll NS, Orellano E, Valls M. Gene expression changes throughout the life cycle allow a bacterial plant pathogen to persist in diverse environmental habitats. PLoS Pathog 2023; 19:e1011888. [PMID: 38113281 PMCID: PMC10763947 DOI: 10.1371/journal.ppat.1011888] [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: 08/31/2023] [Revised: 01/03/2024] [Accepted: 12/07/2023] [Indexed: 12/21/2023] Open
Abstract
Bacterial pathogens exhibit a remarkable ability to persist and thrive in diverse ecological niches. Understanding the mechanisms enabling their transition between habitats is crucial to control dissemination and potential disease outbreaks. Here, we use Ralstonia solanacearum, the causing agent of the bacterial wilt disease, as a model to investigate pathogen adaptation to water and soil, two environments that act as bacterial reservoirs, and compare this information with gene expression in planta. Gene expression in water resembled that observed during late xylem colonization, with an intriguing induction of the type 3 secretion system (T3SS). Alkaline pH and nutrient scarcity-conditions also encountered during late infection stages-were identified as the triggers for this T3SS induction. In the soil environment, R. solanacearum upregulated stress-responses and genes for the use of alternate carbon sources, such as phenylacetate catabolism and the glyoxylate cycle, and downregulated virulence-associated genes. We proved through gain- and loss-of-function experiments that genes associated with the oxidative stress response, such as the regulator OxyR and the catalase KatG, are key for bacterial survival in soil, as their deletion cause a decrease in culturability associated with a premature induction of the viable but non culturable state (VBNC). This work identifies essential factors necessary for R. solanacearum to complete its life cycle and is the first comprehensive gene expression analysis in all environments occupied by a bacterial plant pathogen, providing valuable insights into its biology and adaptation to unexplored habitats.
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Affiliation(s)
- Roger de Pedro-Jové
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Catalonia, Spain
- Centre for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Bellaterra, Catalonia, Spain
| | - Jordi Corral
- Centre for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Bellaterra, Catalonia, Spain
| | - Mercedes Rocafort
- Centre for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Bellaterra, Catalonia, Spain
| | - Marina Puigvert
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Catalonia, Spain
- Centre for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Bellaterra, Catalonia, Spain
| | - Fàtima Latif Azam
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Catalonia, Spain
- Centre for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Bellaterra, Catalonia, Spain
| | - Agustina Vandecaveye
- Área Biología Molecular, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario and Instituto de Biología Molecular y Celular de Rosario, Consejo Nacional de Investigaciones Científicas y Técnicas (IBR-UNR-CONICET), Rosario, Santa Fe, Argentina
| | - Alberto P. Macho
- Shanghai Centre for Plant Stress Biology, CAS Centre for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Carlos Balsalobre
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Catalonia, Spain
| | - Núria S. Coll
- Centre for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Bellaterra, Catalonia, Spain
| | - Elena Orellano
- Área Biología Molecular, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario and Instituto de Biología Molecular y Celular de Rosario, Consejo Nacional de Investigaciones Científicas y Técnicas (IBR-UNR-CONICET), Rosario, Santa Fe, Argentina
| | - Marc Valls
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Catalonia, Spain
- Centre for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Bellaterra, Catalonia, Spain
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4
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Gerson TM, Ott AM, Karney MMA, Socea JN, Ginete DR, Iyer LM, Aravind L, Gary RK, Wing HJ. VirB, a key transcriptional regulator of Shigella virulence, requires a CTP ligand for its regulatory activities. mBio 2023; 14:e0151923. [PMID: 37728345 PMCID: PMC10653881 DOI: 10.1128/mbio.01519-23] [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: 06/23/2023] [Accepted: 07/25/2023] [Indexed: 09/21/2023] Open
Abstract
IMPORTANCE Shigella species cause bacillary dysentery, the second leading cause of diarrheal deaths worldwide. There is a pressing need to identify novel molecular drug targets. Shigella virulence phenotypes are controlled by the transcriptional regulator, VirB. We show that VirB belongs to a fast-evolving, plasmid-borne clade of the ParB superfamily, which has diverged from versions with a distinct cellular role-DNA partitioning. We report that, like classic members of the ParB family, VirB binds a highly unusual ligand, CTP. Mutants predicted to be defective in CTP binding are compromised in a variety of virulence attributes controlled by VirB, likely because these mutants cannot engage DNA. This study (i) reveals that VirB binds CTP, (ii) provides a link between VirB-CTP interactions and Shigella virulence phenotypes, (iii) provides new insight into VirB-CTP-DNA interactions, and (iv) broadens our understanding of the ParB superfamily, a group of bacterial proteins that play critical roles in many bacteria.
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Affiliation(s)
- Taylor M. Gerson
- School of Life Sciences, University of Nevada Las Vegas, Las Vegas, Nevada, USA
| | - Audrey M. Ott
- School of Life Sciences, University of Nevada Las Vegas, Las Vegas, Nevada, USA
| | - Monika M. A. Karney
- School of Life Sciences, University of Nevada Las Vegas, Las Vegas, Nevada, USA
| | - Jillian N. Socea
- School of Life Sciences, University of Nevada Las Vegas, Las Vegas, Nevada, USA
| | - Daren R. Ginete
- School of Life Sciences, University of Nevada Las Vegas, Las Vegas, Nevada, USA
| | | | - L. Aravind
- Computational Biology Branch, National Library of Medicine, Bethesda, Maryland, USA
| | - Ronald K. Gary
- Department of Chemistry and Biochemistry, University of Nevada Las Vegas, Las Vegas, Nevada, USA
| | - Helen J. Wing
- School of Life Sciences, University of Nevada Las Vegas, Las Vegas, Nevada, USA
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5
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Gerson TM, Ott AM, Karney MMA, Socea JN, Ginete DR, Iyer LM, Aravind L, Gary RK, Wing HJ. VirB, a key transcriptional regulator of Shigella virulence, requires a CTP ligand for its regulatory activities. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.16.541010. [PMID: 37293012 PMCID: PMC10245682 DOI: 10.1101/2023.05.16.541010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The VirB protein, encoded by the large virulence plasmid of Shigella spp., is a key transcriptional regulator of virulence genes. Without a functional virB gene, Shigella cells are avirulent. On the virulence plasmid, VirB functions to offset transcriptional silencing mediated by the nucleoid structuring protein, H-NS, which binds and sequesters AT-rich DNA, making it inaccessible for gene expression. Thus, gaining a mechanistic understanding of how VirB counters H-NS-mediated silencing is of considerable interest. VirB is unusual in that it does not resemble classic transcription factors. Instead, its closest relatives are found in the ParB superfamily, where the best-characterized members function in faithful DNA segregation before cell division. Here, we show that VirB is a fast-evolving member of this superfamily and report for the first time that the VirB protein binds a highly unusual ligand, CTP. VirB binds this nucleoside triphosphate preferentially and with specificity. Based on alignments with the best-characterized members of the ParB family, we identify amino acids of VirB likely to bind CTP. Substitutions in these residues disrupt several well-documented activities of VirB, including its anti-silencing activity at a VirB-dependent promoter, its role in generating a Congo red positive phenotype in Shigella , and the ability of the VirB protein to form foci in the bacterial cytoplasm when fused to GFP. Thus, this work is the first to show that VirB is a bona fide CTP-binding protein and links Shigella virulence phenotypes to the nucleoside triphosphate, CTP. Importance Shigella species cause bacillary dysentery (shigellosis), the second leading cause of diarrheal deaths worldwide. With growing antibiotic resistance, there is a pressing need to identify novel molecular drug targets. Shigella virulence phenotypes are controlled by the transcriptional regulator, VirB. We show that VirB belongs to a fast-evolving, primarily plasmid-borne clade of the ParB superfamily, which has diverged from versions that have a distinct cellular role - DNA partitioning. We are the first to report that, like classic members of the ParB family, VirB binds a highly unusual ligand, CTP. Mutants predicted to be defective in CTP binding are compromised in a variety of virulence attributes controlled by VirB. This study i) reveals that VirB binds CTP, ii) provides a link between VirB-CTP interactions and Shigella virulence phenotypes, and iii) broadens our understanding of the ParB superfamily, a group of bacterial proteins that play critical roles in many different bacteria.
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Affiliation(s)
- Taylor M. Gerson
- School of Life Sciences, University of Nevada Las Vegas, Las Vegas, NV 89154-4004, USA
| | - Audrey M. Ott
- School of Life Sciences, University of Nevada Las Vegas, Las Vegas, NV 89154-4004, USA
| | - Monika MA. Karney
- School of Life Sciences, University of Nevada Las Vegas, Las Vegas, NV 89154-4004, USA
| | - Jillian N. Socea
- School of Life Sciences, University of Nevada Las Vegas, Las Vegas, NV 89154-4004, USA
| | - Daren R. Ginete
- School of Life Sciences, University of Nevada Las Vegas, Las Vegas, NV 89154-4004, USA
| | - Lakshminarayan M. Iyer
- Computational Biology Branch, 8600 Rockville Pike, Building 38A, Room 5N505, National Library of Medicine, Bethesda, MD 20894
| | - L. Aravind
- Computational Biology Branch, 8600 Rockville Pike, Building 38A, Room 5N505, National Library of Medicine, Bethesda, MD 20894
| | - Ronald K. Gary
- Department of Chemistry and Biochemistry, University of Nevada Las Vegas, Las Vegas, NV 89154-4003
| | - Helen J. Wing
- School of Life Sciences, University of Nevada Las Vegas, Las Vegas, NV 89154-4004, USA
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6
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Picker MA, Karney MMA, Gerson TM, Karabachev A, Duhart J, McKenna J, Wing H. Localized modulation of DNA supercoiling, triggered by the Shigella anti-silencer VirB, is sufficient to relieve H-NS-mediated silencing. Nucleic Acids Res 2023; 51:3679-3695. [PMID: 36794722 PMCID: PMC10164555 DOI: 10.1093/nar/gkad088] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Revised: 01/27/2023] [Accepted: 01/31/2023] [Indexed: 02/17/2023] Open
Abstract
In Bacteria, nucleoid structuring proteins govern nucleoid dynamics and regulate transcription. In Shigella spp., at ≤30°C, the histone-like nucleoid structuring protein (H-NS) transcriptionally silences many genes on the large virulence plasmid. Upon a switch to 37°C, VirB, a DNA binding protein and key transcriptional regulator of Shigella virulence, is produced. VirB functions to counter H-NS-mediated silencing in a process called transcriptional anti-silencing. Here, we show that VirB mediates a loss of negative DNA supercoils from our plasmid-borne, VirB-regulated PicsP-lacZ reporter in vivo. The changes are not caused by a VirB-dependent increase in transcription, nor do they require the presence of H-NS. Instead, the VirB-dependent change in DNA supercoiling requires the interaction of VirB with its DNA binding site, a critical first step in VirB-dependent gene regulation. Using two complementary approaches, we show that VirB:DNA interactions in vitro introduce positive supercoils in plasmid DNA. Subsequently, by exploiting transcription-coupled DNA supercoiling, we reveal that a localized loss of negative supercoils is sufficient to alleviate H-NS-mediated transcriptional silencing independently of VirB. Together, our findings provide novel insight into VirB, a central regulator of Shigella virulence and, more broadly, a molecular mechanism that offsets H-NS-dependent silencing of transcription in bacteria.
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Affiliation(s)
- Michael A Picker
- School of Life Sciences, University of Nevada Las Vegas, Las Vegas, NV 89154-4004, USA
| | - Monika M A Karney
- School of Life Sciences, University of Nevada Las Vegas, Las Vegas, NV 89154-4004, USA
| | - Taylor M Gerson
- School of Life Sciences, University of Nevada Las Vegas, Las Vegas, NV 89154-4004, USA
| | | | - Juan C Duhart
- School of Life Sciences, University of Nevada Las Vegas, Las Vegas, NV 89154-4004, USA
| | - Joy A McKenna
- School of Life Sciences, University of Nevada Las Vegas, Las Vegas, NV 89154-4004, USA
| | - Helen J Wing
- School of Life Sciences, University of Nevada Las Vegas, Las Vegas, NV 89154-4004, USA
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7
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Dadinova LA, Petoukhov MV, Gordienko AM, Manuvera VA, Lazarev VN, Rakitina TV, Mozhaev AA, Peters GS, Shtykova EV. Nucleoid-Associated Proteins HU and IHF: Oligomerization in Solution and Hydrodynamic Properties. BIOCHEMISTRY. BIOKHIMIIA 2023; 88:640-654. [PMID: 37331710 DOI: 10.1134/s0006297923050073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Revised: 03/10/2023] [Accepted: 03/23/2023] [Indexed: 06/20/2023]
Abstract
Structure and function of bacterial nucleoid is controlled by the nucleoid-associated proteins (NAP). In any phase of growth, various NAPs, acting sequentially, condense nucleoid and facilitate formation of its transcriptionally active structure. However, in the late stationary phase, only one of the NAPs, Dps protein, is strongly expressed, and DNA-protein crystals are formed that transform nucleoid into a static, transcriptionally inactive structure, effectively protected from the external influences. Discovery of crystal structures in living cells and association of this phenomenon with the bacterial resistance to antibiotics has aroused great interest in studying this phenomenon. The aim of this work is to obtain and compare structures of two related NAPs (HU and IHF), since they are the ones that accumulate in the cell at the late stationary stage of growth, which precedes formation of the protective DNA-Dps crystalline complex. For structural studies, two complementary methods were used in the work: small-angle X-ray scattering (SAXS) as the main method for studying structure of proteins in solution, and dynamic light scattering as a complementary one. To interpret the SAXS data, various approaches and computer programs were used (in particular, the evaluation of structural invariants, rigid body modeling and equilibrium mixture analysis in terms of the volume fractions of its components were applied), which made it possible to determine macromolecular characteristics and obtain reliable 3D structural models of various oligomeric forms of HU and IHF proteins with ~2 nm resolution typical for SAXS. It was shown that these proteins oligomerize in solution to varying degrees, and IHF is characterized by the presence of large oligomers consisting of initial dimers arranged in a chain. An analysis of the experimental and published data made it possible to hypothesize that just before the Dps expression, it is IHF that forms toroidal structures previously observed in vivo and prepares the platform for formation of DNA-Dps crystals. The results obtained are necessary for further investigation of the phenomenon of biocrystal formation in bacterial cells and finding ways to overcome resistance of various pathogens to external conditions.
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Affiliation(s)
- Liubov A Dadinova
- Shubnikov Institute of Crystallography, Federal Scientific Research Centre "Crystallography and Photonics", Russian Academy of Sciences, Moscow, 119333, Russia
| | - Maxim V Petoukhov
- Shubnikov Institute of Crystallography, Federal Scientific Research Centre "Crystallography and Photonics", Russian Academy of Sciences, Moscow, 119333, Russia
| | - Alexander M Gordienko
- Shubnikov Institute of Crystallography, Federal Scientific Research Centre "Crystallography and Photonics", Russian Academy of Sciences, Moscow, 119333, Russia
| | - Valentin A Manuvera
- Lopukhin Federal Research and Clinical Center of Physical-Chemical Medicine, Federal Medical Biological Agency, Moscow, 119435, Russia
- Moscow Institute of Physics and Technology (State University), Dolgoprudny, Moscow Region, 141701, Russia
| | - Vassili N Lazarev
- Lopukhin Federal Research and Clinical Center of Physical-Chemical Medicine, Federal Medical Biological Agency, Moscow, 119435, Russia
- Moscow Institute of Physics and Technology (State University), Dolgoprudny, Moscow Region, 141701, Russia
| | - Tatiana V Rakitina
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, 117997, Russia
- National Research Centre "Kurchatov Institute", Moscow, 123182, Russia
| | - Andrey A Mozhaev
- Shubnikov Institute of Crystallography, Federal Scientific Research Centre "Crystallography and Photonics", Russian Academy of Sciences, Moscow, 119333, Russia
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, 117997, Russia
| | - Georgy S Peters
- National Research Centre "Kurchatov Institute", Moscow, 123182, Russia
| | - Eleonora V Shtykova
- Shubnikov Institute of Crystallography, Federal Scientific Research Centre "Crystallography and Photonics", Russian Academy of Sciences, Moscow, 119333, Russia.
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8
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Picker MA, Karney MMA, Gerson TM, Karabachev AD, Duhart JC, McKenna JA, Wing HJ. Localized modulation of DNA supercoiling, triggered by the Shigella anti-silencer VirB, is sufficient to relieve H-NS-mediated silencing. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.09.523335. [PMID: 36711906 PMCID: PMC9882051 DOI: 10.1101/2023.01.09.523335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
In Bacteria, nucleoid structuring proteins govern nucleoid dynamics and regulate transcription. In Shigella spp ., at ≤ 30 °C, the histone-like nucleoid structuring protein (H-NS) transcriptionally silences many genes on the large virulence plasmid. Upon a switch to 37 °C, VirB, a DNA binding protein and key transcriptional regulator of Shigella virulence, is produced. VirB functions to counter H-NS-mediated silencing in a process called transcriptional anti-silencing. Here, we show that VirB mediates a loss of negative DNA supercoils from our plasmid-borne, VirB-regulated PicsP-lacZ reporter, in vivo . The changes are not caused by a VirB-dependent increase in transcription, nor do they require the presence of H-NS. Instead, the VirB-dependent change in DNA supercoiling requires the interaction of VirB with its DNA binding site, a critical first step in VirB-dependent gene regulation. Using two complementary approaches, we show that VirB:DNA interactions in vitro introduce positive supercoils in plasmid DNA. Subsequently, by exploiting transcription-coupled DNA supercoiling, we reveal that a localized loss of negative supercoils is sufficient to alleviate H-NS-mediated transcriptional silencing, independently of VirB. Together, our findings provide novel insight into VirB, a central regulator of Shigella virulence and more broadly, a molecular mechanism that offsets H-NS-dependent silencing of transcription in bacteria.
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9
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Degradation of gene silencer is essential for expression of foreign genes and bacterial colonization of the mammalian gut. Proc Natl Acad Sci U S A 2022; 119:e2210239119. [PMID: 36161931 DOI: 10.1073/pnas.2210239119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Horizontal gene transfer drives bacterial evolution. To confer new properties, horizontally acquired genes must overcome gene silencing by nucleoid-associated proteins, such as the heat-stable nucleoid structuring (H-NS) protein. Enteric bacteria possess proteins that displace H-NS from foreign genes, form nonfunctional oligomers with H-NS, and degrade H-NS, raising the question of whether any of these mechanisms play a role in overcoming foreign gene silencing in vivo. To answer this question, we mutagenized the hns gene and identified a variant specifying an H-NS protein that binds foreign DNA and silences expression of the corresponding genes, like wild-type H-NS, but resists degradation by the Lon protease. Critically, Escherichia coli expressing this variant alone fails to produce curli, which are encoded by foreign genes and required for biofilm formation, and fails to colonize the murine gut. Our findings establish that H-NS proteolysis is a general mechanism of derepressing foreign genes and essential for colonization of mammalian hosts.
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10
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Forrest D, Warman EA, Erkelens AM, Dame RT, Grainger DC. Xenogeneic silencing strategies in bacteria are dictated by RNA polymerase promiscuity. Nat Commun 2022; 13:1149. [PMID: 35241653 PMCID: PMC8894471 DOI: 10.1038/s41467-022-28747-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Accepted: 02/07/2022] [Indexed: 12/13/2022] Open
Abstract
Horizontal gene transfer facilitates dissemination of favourable traits among bacteria. However, foreign DNA can also reduce host fitness: incoming sequences with a higher AT content than the host genome can misdirect transcription. Xenogeneic silencing proteins counteract this by modulating RNA polymerase binding. In this work, we compare xenogeneic silencing strategies of two distantly related model organisms: Escherichia coli and Bacillus subtilis. In E. coli, silencing is mediated by the H-NS protein that binds extensively across horizontally acquired genes. This prevents spurious non-coding transcription, mostly intragenic in origin. By contrast, binding of the B. subtilis Rok protein is more targeted and mostly silences expression of functional mRNAs. The difference reflects contrasting transcriptional promiscuity in E. coli and B. subtilis, largely attributable to housekeeping RNA polymerase σ factors. Thus, whilst RNA polymerase specificity is key to the xenogeneic silencing strategy of B. subtilis, transcriptional promiscuity must be overcome to silence horizontally acquired DNA in E. coli. Bacteria use specific silencing proteins to prevent spurious transcription of horizontally acquired DNA. Here, Forrest et al. describe differences in silencing strategies between E. coli and Bacillus subtilis, driven by the respective specificities of the silencing protein and the RNA polymerase in each organism.
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Affiliation(s)
- David Forrest
- School of Biosciences, University of Birmingham, Edgbaston, B15 2TT, UK
| | - Emily A Warman
- School of Biosciences, University of Birmingham, Edgbaston, B15 2TT, UK
| | - Amanda M Erkelens
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333CC, Leiden, The Netherlands
| | - Remus T Dame
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333CC, Leiden, The Netherlands.,Centre for Microbial Cell Biology, Leiden University, Einsteinweg 55, 2333CC, Leiden, The Netherlands
| | - David C Grainger
- School of Biosciences, University of Birmingham, Edgbaston, B15 2TT, UK.
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11
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Dong H, Zhao Y, Bi C, Han Y, Zhang J, Bai X, Zhai G, Zhang H, Tian S, Hu D, Xu L, Zhang K. TmcA functions as a lysine 2-hydroxyisobutyryltransferase to regulate transcription. Nat Chem Biol 2022; 18:142-151. [PMID: 34903851 DOI: 10.1038/s41589-021-00906-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 09/23/2021] [Indexed: 02/05/2023]
Abstract
Protein lysine 2-hydroxyisobutyrylation (Khib) has recently been shown to play a critical role in the regulation of cellular processes. However, the mechanism and functional consequence of Khib in prokaryotes remain unclear. Here we report that TmcA, an RNA acetyltransferase, functions as a lysine 2-hydroxyisobutyryltransferase in the regulation of transcription. We show that TmcA can effectively catalyze Khib both in vitro and intracellularly, and that R502 is a key site for the Khib catalytic activity of TmcA. Using quantitative proteomics, we identified 467 endogenous candidates targeted by TmcA for Khib in Escherichia coli. Interestingly, we demonstrate that TmcA can specifically modulate the DNA-binding activity of H-NS, a nucleoid-associated protein, by catalysis of Khib at K121. Furthermore, this TmcA-targeted Khib regulates transcription of acid-resistance genes and enhances E. coli survival under acid stress. Our study reveals transcription regulation mediated by TmcA-catalyzed Khib for bacterial acid resistance.
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Affiliation(s)
- Hanyang Dong
- The Province and Ministry Co-sponsored Collaborative Innovation Center for Medical Epigenetics, Key Laboratory of Breast Cancer Prevention and Therapy (Ministry of Education), Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University Cancer Institute and Hospital, Tianjin Medical University General Hospital, Tianjin Medical University, Tianjin, China
- The Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Department of Biochemistry and Molecular Biology, Shantou University Medical College, Shantou, China
| | - Yujie Zhao
- The Province and Ministry Co-sponsored Collaborative Innovation Center for Medical Epigenetics, Key Laboratory of Breast Cancer Prevention and Therapy (Ministry of Education), Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University Cancer Institute and Hospital, Tianjin Medical University General Hospital, Tianjin Medical University, Tianjin, China
| | - Changfen Bi
- Tianjin Key Laboratory of Radiation Medicine and Molecular Nuclear Medicine, Institute of Radiation Medicine, Peking Union Medical College & Chinese Academy of Medical Sciences, Tianjin, China
| | - Yue Han
- The Province and Ministry Co-sponsored Collaborative Innovation Center for Medical Epigenetics, Key Laboratory of Breast Cancer Prevention and Therapy (Ministry of Education), Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University Cancer Institute and Hospital, Tianjin Medical University General Hospital, Tianjin Medical University, Tianjin, China
| | - Jianji Zhang
- The Province and Ministry Co-sponsored Collaborative Innovation Center for Medical Epigenetics, Key Laboratory of Breast Cancer Prevention and Therapy (Ministry of Education), Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University Cancer Institute and Hospital, Tianjin Medical University General Hospital, Tianjin Medical University, Tianjin, China
| | - Xue Bai
- The Province and Ministry Co-sponsored Collaborative Innovation Center for Medical Epigenetics, Key Laboratory of Breast Cancer Prevention and Therapy (Ministry of Education), Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University Cancer Institute and Hospital, Tianjin Medical University General Hospital, Tianjin Medical University, Tianjin, China
| | - Guijin Zhai
- The Province and Ministry Co-sponsored Collaborative Innovation Center for Medical Epigenetics, Key Laboratory of Breast Cancer Prevention and Therapy (Ministry of Education), Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University Cancer Institute and Hospital, Tianjin Medical University General Hospital, Tianjin Medical University, Tianjin, China
| | - Hui Zhang
- The Province and Ministry Co-sponsored Collaborative Innovation Center for Medical Epigenetics, Key Laboratory of Breast Cancer Prevention and Therapy (Ministry of Education), Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University Cancer Institute and Hospital, Tianjin Medical University General Hospital, Tianjin Medical University, Tianjin, China
| | - Shanshan Tian
- The Province and Ministry Co-sponsored Collaborative Innovation Center for Medical Epigenetics, Key Laboratory of Breast Cancer Prevention and Therapy (Ministry of Education), Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University Cancer Institute and Hospital, Tianjin Medical University General Hospital, Tianjin Medical University, Tianjin, China
| | - Deqing Hu
- Tianjin Key Laboratory of Medical Epigenetics, Department of Cell Biology, Tianjin Medical University, Tianjin, China
| | - Liyan Xu
- The Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Department of Biochemistry and Molecular Biology, Shantou University Medical College, Shantou, China
| | - Kai Zhang
- The Province and Ministry Co-sponsored Collaborative Innovation Center for Medical Epigenetics, Key Laboratory of Breast Cancer Prevention and Therapy (Ministry of Education), Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University Cancer Institute and Hospital, Tianjin Medical University General Hospital, Tianjin Medical University, Tianjin, China.
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12
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Fang YL, Cui Y, Zhou L, Thawai C, Naqvi TA, Zhang HY, He YW. H-NS family protein MvaU downregulates phenazine-1-carboxylic acid (PCA) biosynthesis via binding to an AT-rich region within the promoter of the phz2 gene cluster in the rhizobacterium Pseudomonas strain PA1201. Synth Syst Biotechnol 2021; 6:262-271. [PMID: 34584994 PMCID: PMC8455314 DOI: 10.1016/j.synbio.2021.09.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 09/08/2021] [Accepted: 09/10/2021] [Indexed: 11/06/2022] Open
Abstract
Histone-like nucleoid-structuring (H-NS) proteins are key regulators in gene expression silencing and in nucleoid compaction. The H-NS family member proteins MvaU in Pseudomonas aeruginosa are thought to bind the same AT-rich regions of chromosomes and function to coordinate the control of a common set of genes. Here, we explored the molecular mechanism by which MvaU controls PCA biosynthesis in P. aeruginosa PA1201. We present evidence suggesting that MvaU is self-regulated. Deletion of mvaU significantly increased PCA production, and PCA production sharply decreased when mvaU was over-expressed. MvaU transcriptionally repressed phz2 cluster expression and consequently reduced PCA biosynthesis. β-galactosidase assays confirmed that base pairing near the −35 box is required when MvaU regulates PCA production in PA1201. Electrophoretic mobility shift assays (EMSA) and additional point mutation analysis demonstrated that MvaU directly bound to an AT-rich motif within the promoter of the phz2 cluster. Chromatin immunoprecipitation (ChIP) analysis also indicated that MvaU directly bound to the P5 region of the phz2 cluster promoter. MvaU repression of PCA biosynthesis was independent of QscR and OxyR in PA1201 and neither PCA or H2O2 were the environmental signals that induced mvaU expression. These findings detail a new MvaU-dependent regulatory pathway of PCA biosynthesis in PA1201 and provide a foundation to increase PCA fermentation titer by genetic engineering.
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Affiliation(s)
- Yun-Ling Fang
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic and Developmental Sciences, SJTU-Shanghai Nong Le Joint R&D Center on Biopesticides and Biofertilizers, Shanghai Jiao Tong University (SJTU), Shanghai, 200240, China
| | - Ying Cui
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic and Developmental Sciences, SJTU-Shanghai Nong Le Joint R&D Center on Biopesticides and Biofertilizers, Shanghai Jiao Tong University (SJTU), Shanghai, 200240, China
| | - Lian Zhou
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic and Developmental Sciences, SJTU-Shanghai Nong Le Joint R&D Center on Biopesticides and Biofertilizers, Shanghai Jiao Tong University (SJTU), Shanghai, 200240, China
| | - Chitti Thawai
- Department of Biology, Faculty of Science, King Mongkut's Institute of Technology Ladkrabang, Bangkok, Thailand
| | - Tatheer Alam Naqvi
- Department of Biotechnology, COMSATS University Islamabad, Abbottabad Campus, Abbottabad, Pakistan
| | - Hong-Yan Zhang
- Shanghai Nong Le Biological Products Company Limited, Shanghai, 201419, China
| | - Ya-Wen He
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic and Developmental Sciences, SJTU-Shanghai Nong Le Joint R&D Center on Biopesticides and Biofertilizers, Shanghai Jiao Tong University (SJTU), Shanghai, 200240, China
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13
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Zhao X, Remington JM, Schneebeli ST, Arold ST, Li J. Molecular Basis for Environment Sensing by a Nucleoid-Structuring Bacterial Protein Filament. J Phys Chem Lett 2021; 12:7878-7884. [PMID: 34382809 PMCID: PMC9346976 DOI: 10.1021/acs.jpclett.1c01710] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The histone-like nucleoid structuring (H-NS) protein controls the expression of hundreds of genes in Gram-positive bacteria through its capability to coat and condense DNA. This mechanism requires the formation of superhelical H-NS protein filaments that are sensitive to temperature and salinity, allowing H-NS to act as an environment sensor. We use multiscale modeling and simulations to obtain detailed insights into the mechanism of H-NS filament's sensitivity to environmental changes. Through the simulations of the superhelical H-NS filament, we reveal how different environments induce heterogeneity of H-NS monomers. Further, we observe that transient self-association within the H-NS filament creates temperature-inducible strain and might mildly oppose DNA binding. We also probe different H-NS-DNA complex architectures and show that complexation enhances the stability of both DNA and H-NS superhelices. Overall, our results provide unprecedented molecular insights into the environmental sensing and DNA interactions of a prototypical nucleoid-structuring bacterial protein filament.
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Affiliation(s)
- Xiaochuan Zhao
- Departments of Chemistry and Materials Science, University of Vermont, Burlington VT 05405
| | - Jacob M. Remington
- Departments of Chemistry and Materials Science, University of Vermont, Burlington VT 05405
| | - Severin T. Schneebeli
- Departments of Chemistry and Materials Science, University of Vermont, Burlington VT 05405
| | - Stefan T. Arold
- King Abdullah University of Science and Technology (KAUST), Computational Bioscience Research Center (CBRC), Biological and Environmental Science and Engineering (BESE), Thuwal, 23955-6900, Saudi Arabia
- Centre de Biologie Structurale, CNRS, INSERM, Université de Montpellier, 34090 Montpellier, France
| | - Jianing Li
- Departments of Chemistry and Materials Science, University of Vermont, Burlington VT 05405
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14
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Zhao X, Yang F, Wang Y, Zhang Y. hns mRNA downregulates the expression of galU and attenuates the motility of Salmonella enterica serovar Typhi. Int J Med Microbiol 2021; 311:151525. [PMID: 34340061 DOI: 10.1016/j.ijmm.2021.151525] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2021] [Revised: 07/11/2021] [Accepted: 07/25/2021] [Indexed: 10/20/2022] Open
Abstract
Recently, multiple bifunctional RNAs have been discovered, which can both be translated into proteins and play regulatory roles. hns encodes the global gene silencing factor H-NS, which is widespread in Gram-negative bacteria. This study reported that hns mRNA of Salmonella enterica serovar Typhi (S. Typhi) was a bifunctional RNA that could act as an antisense RNA downregulating the expression of galU, the coding gene of uridine triphosphate-glucose-1-phosphate uridylyltransferase, and attenuating bacterial motility. galU, which is located at the opposite strand of hns, was identified to have a long 3'-untranslated region that overlapped with hns and could be processed to produce short RNA fragments. The overexpression of hns mRNA inhibited the expression of galU. The deletion of galU attenuated the motility of S. Typhi, while the complementation of galU nearly restored the phenotype. Overexpressing hns mRNA in the wild-type strain of S. Typhi inhibited the motility and the expression of flagellar genes, while overexpressing hns mRNA in the galU-deletion mutant did not influence bacterial motility. In conclusion, hns mRNA has been identified to be a new bifunctional RNA that attenuates the motility of S. Typhi by downregulating the expression of galU.
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Affiliation(s)
- Xin Zhao
- Department of Nuclear Medicine, Nanjing First Hospital, Nanjing Medical University, Nanjing, Jiangsu, 210006, China.
| | - Fanfan Yang
- Department of Biochemistry and Molecular Biology, School of Medicine, Jiangsu University, Zhenjiang, Jiangsu, 212013, China.
| | - Yurou Wang
- Department of Biochemistry and Molecular Biology, School of Medicine, Jiangsu University, Zhenjiang, Jiangsu, 212013, China.
| | - Ying Zhang
- Department of Biochemistry and Molecular Biology, School of Medicine, Jiangsu University, Zhenjiang, Jiangsu, 212013, China.
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15
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A Histone-Like Nucleoid Structuring Protein Regulates Several Virulence Traits in Burkholderia multivorans. Appl Environ Microbiol 2021; 87:e0036921. [PMID: 33931418 PMCID: PMC8231446 DOI: 10.1128/aem.00369-21] [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] [Indexed: 12/12/2022] Open
Abstract
Burkholderia cepacia complex bacteria comprise opportunistic pathogens causing chronic respiratory infections in cystic fibrosis (CF) patients. These microorganisms produce an exopolysaccharide named cepacian, which is considered a virulence determinant. To find genes implicated in the regulation of cepacian biosynthesis, we characterized an evolved nonmucoid variant (17616nmv) derived from the ancestor, Burkholderia multivorans ATCC 17616, after prolonged stationary phase. Lack of cepacian biosynthesis was correlated with downregulation of the expression of bce genes implicated in its biosynthesis. Furthermore, genome sequencing of the variant identified the transposition of the mobile element IS406 upstream of the coding sequence of an hns-like gene (Bmul_0158) encoding a histone-like nucleoid structuring (H-NS) protein, a known global transcriptional repressor. This insertion sequence (IS) element upregulated the expression of Bmul_0158 by 4-fold. Transcriptome analysis identified the global effects of this mutation on gene expression, with major changes in genes implicated in motility, pilus synthesis, type VI secretion, and chromosome-associated functions. Concomitant with these differences, the nonmucoid variant displays reduced adherence to a CF lung bronchial cell line and reduced surface hydrophobicity and forms smaller cellular aggregates but has an increase in swimming and swarming motilities. Finally, analysis of the GC content of the upstream region of differentially expressed genes led to the identification of various genomic regions, possibly acquired by horizontal gene transfer, which were transcriptionally repressed by the increased expression of the Bmul_0158 gene in the 17616nmv strain. Taken together, the results revealed a significant role for this H-NS protein in the regulation of B. multivorans persistence- and virulence-associated genes. IMPORTANCE Members of the histone-like nucleoid structuring (H-NS) family of proteins, present in many bacteria, are important global regulators of gene expression. Many of the regulated genes were acquired horizontally and include pathogenicity islands and prophages, among others. Additionally, H-NS can play a structural role by bridging and compacting DNA, fulfilling a crucial role in cell physiology. Several virulence phenotypes have been frequently identified in several bacteria as dependent on H-NS activity. Here, we describe an H-NS-like protein of the opportunistic pathogen Burkholderia multivorans, a species commonly infecting the respiratory tract of cystic fibrosis patients. Our results indicate that this protein is involved in regulating virulence traits such as exopolysaccharide biosynthesis, adhesion to biotic surfaces, cellular aggregation, and motility. Furthermore, this H-NS-like protein is one out of eight orthologs present in the B. multivorans ATCC 17616 genome, posing relevant questions to be investigated on how these proteins coordinate the expression of virulence traits.
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16
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Abstract
Pathogenic Vibrio cholerae strains express multiple virulence factors that are encoded by bacteriophage and chromosomal islands. These include cholera toxin and the intestinal colonization pilus called the toxin-coregulated pilus, which are essential for causing severe disease in humans. However, it is presently unclear how the expression of these horizontally acquired accessory virulence genes can be efficiently integrated with preexisting transcriptional programs that are presumably fine-tuned for optimal expression in V. cholerae before its conversion to a human pathogen. Here, we report the role of a transcriptional regulator (TsrA) in silencing horizontally acquired genes encoding important virulence factors. We propose that this factor could be critical to the efficient acquisition of accessory virulence genes by silencing their expression until other signals trigger their transcriptional activation within the host. Vibrio cholerae is a globally important pathogen responsible for the severe epidemic diarrheal disease called cholera. The current and ongoing seventh pandemic of cholera is caused by El Tor strains, which have completely replaced the sixth-pandemic classical strains of V. cholerae. To successfully establish infection and disseminate to new victims, V. cholerae relies on key virulence factors encoded on horizontally acquired genetic elements. The expression of these factors relies on the regulatory architecture that coordinates the timely expression of virulence determinants during host infection. Here, we apply transcriptomics and structural modeling to understand how type VI secretion system regulator A (TsrA) affects gene expression in both the classical and El Tor biotypes of V. cholerae. We find that TsrA acts as a negative regulator of V. cholerae virulence genes encoded on horizontally acquired genetic elements. The TsrA regulon comprises genes encoding cholera toxin (CT), the toxin-coregulated pilus (TCP), and the type VI secretion system (T6SS), as well as genes involved in biofilm formation. The majority of the TsrA regulon is carried on horizontally acquired AT-rich genetic islands whose loss or acquisition could be directly ascribed to the differences between the classical and El Tor strains studied. Our modeling predicts that the TsrA protein is a structural homolog of the histone-like nucleoid structuring protein (H-NS) oligomerization domain and is likely capable of forming higher-order superhelical structures, potentially with DNA. These findings describe how TsrA can integrate into the intricate V. cholerae virulence gene expression program, controlling gene expression through transcriptional silencing.
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17
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Fitzgerald S, Kary SC, Alshabib EY, MacKenzie KD, Stoebel DM, Chao TC, Cameron ADS. Redefining the H-NS protein family: a diversity of specialized core and accessory forms exhibit hierarchical transcriptional network integration. Nucleic Acids Res 2020; 48:10184-10198. [PMID: 32894292 PMCID: PMC7544231 DOI: 10.1093/nar/gkaa709] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 08/07/2020] [Accepted: 08/23/2020] [Indexed: 12/27/2022] Open
Abstract
H-NS is a nucleoid structuring protein and global repressor of virulence and horizontally-acquired genes in bacteria. H-NS can interact with itself or with homologous proteins, but protein family diversity and regulatory network overlap remain poorly defined. Here, we present a comprehensive phylogenetic analysis that revealed deep-branching clades, dispelling the presumption that H-NS is the progenitor of varied molecular backups. Each clade is composed exclusively of either chromosome-encoded or plasmid-encoded proteins. On chromosomes, stpA and newly discovered hlpP are core genes in specific genera, whereas hfp and newly discovered hlpC are sporadically distributed. Six clades of H-NS plasmid proteins (Hpp) exhibit ancient and dedicated associations with plasmids, including three clades with fidelity for plasmid incompatibility groups H, F or X. A proliferation of H-NS homologs in Erwiniaceae includes the first observation of potentially co-dependent H-NS forms. Conversely, the observed diversification of oligomerization domains may facilitate stable co-existence of divergent homologs in a genome. Transcriptomic and proteomic analysis in Salmonella revealed regulatory crosstalk and hierarchical control of H-NS homologs. We also discovered that H-NS is both a repressor and activator of Salmonella Pathogenicity Island 1 gene expression, and both regulatory modes are restored by Sfh (HppH) in the absence of H-NS.
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Affiliation(s)
- Stephen Fitzgerald
- Department of Biology, University of Regina, Regina, Saskatchewan S4S 0A2, Canada.,Division of Immunity and Infection, The Roslin Institute and R(D)SVS, University of Edinburgh, Edinburgh EH25 9RG, UK
| | - Stefani C Kary
- Department of Biology, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
| | - Ebtihal Y Alshabib
- Department of Biology, University of Regina, Regina, Saskatchewan S4S 0A2, Canada.,Institute for Microbial Systems and Society, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
| | - Keith D MacKenzie
- Department of Biology, University of Regina, Regina, Saskatchewan S4S 0A2, Canada.,Institute for Microbial Systems and Society, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
| | - Daniel M Stoebel
- Department of Biology, Harvey Mudd College, Claremont, CA 91711, USA
| | - Tzu-Chiao Chao
- Department of Biology, University of Regina, Regina, Saskatchewan S4S 0A2, Canada.,Institute of Environmental Change and Society, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
| | - Andrew D S Cameron
- Department of Biology, University of Regina, Regina, Saskatchewan S4S 0A2, Canada.,Institute for Microbial Systems and Society, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
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18
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Borriello G, Russo V, Paradiso R, Riccardi MG, Criscuolo D, Verde G, Marasco R, Pedone PV, Galiero G, Baglivo I. Different Impacts of MucR Binding to the babR and virB Promoters on Gene Expression in Brucella abortus 2308. Biomolecules 2020; 10:biom10050788. [PMID: 32438765 PMCID: PMC7277663 DOI: 10.3390/biom10050788] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 05/12/2020] [Accepted: 05/12/2020] [Indexed: 12/27/2022] Open
Abstract
The protein MucR from Brucella abortus has been described as a transcriptional regulator of many virulence genes. It is a member of the Ros/MucR family comprising proteins that control the expression of genes important for the successful interaction of α-proteobacteria with their eukaryotic hosts. Despite clear evidence of the role of MucR in repressing virulence genes, no study has been carried out so far demonstrating the direct interaction of this protein with the promoter of its target gene babR encoding a LuxR-like regulator repressing virB genes. In this study, we show for the first time the ability of MucR to bind the promoter of babR in electrophoretic mobility shift assays demonstrating a direct role of MucR in repressing this gene. Furthermore, we demonstrate that MucR can bind the virB gene promoter. Analyses by RT-qPCR showed no significant differences in the expression level of virB genes in Brucella abortus CC092 lacking MucR compared to the wild-type Brucella abortus strain, indicating that MucR binding to the virB promoter has little impact on virB gene expression in B. abortus 2308. The MucR modality to bind the two promoters analyzed supports our previous hypothesis that this is a histone-like protein never found before in Brucella.
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Affiliation(s)
- Giorgia Borriello
- Experimental Zooprophylactic Institute of Southern Italy, via Salute, 2, 80055 Portici, Italy; (G.B.); (R.P.); (M.G.R.); (D.C.)
| | - Veronica Russo
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, University of Campania “Luigi Vanvitelli”, via Vivaldi—43, 81100 Caserta, Italy; (V.R.); (R.M.); (P.V.P.)
| | - Rubina Paradiso
- Experimental Zooprophylactic Institute of Southern Italy, via Salute, 2, 80055 Portici, Italy; (G.B.); (R.P.); (M.G.R.); (D.C.)
| | - Marita Georgia Riccardi
- Experimental Zooprophylactic Institute of Southern Italy, via Salute, 2, 80055 Portici, Italy; (G.B.); (R.P.); (M.G.R.); (D.C.)
| | - Daniela Criscuolo
- Experimental Zooprophylactic Institute of Southern Italy, via Salute, 2, 80055 Portici, Italy; (G.B.); (R.P.); (M.G.R.); (D.C.)
| | - Gaetano Verde
- Institute of Genetics and Biophysics (IGB) “Adriano Buzzati-Traverso”, Consiglio Nazionale delle Ricerche (CNR), 80134 Naples, Italy;
- Flomics Biotech, Carrer Dr. Aiguader 88, 08003 Barcelona, Spain
| | - Rosangela Marasco
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, University of Campania “Luigi Vanvitelli”, via Vivaldi—43, 81100 Caserta, Italy; (V.R.); (R.M.); (P.V.P.)
| | - Paolo Vincenzo Pedone
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, University of Campania “Luigi Vanvitelli”, via Vivaldi—43, 81100 Caserta, Italy; (V.R.); (R.M.); (P.V.P.)
| | - Giorgio Galiero
- Experimental Zooprophylactic Institute of Southern Italy, via Salute, 2, 80055 Portici, Italy; (G.B.); (R.P.); (M.G.R.); (D.C.)
- Correspondence: (G.G.); (I.B.); Tel.: +39-081-7865201 (G.G.); +39-0823-274598 (I.B.)
| | - Ilaria Baglivo
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, University of Campania “Luigi Vanvitelli”, via Vivaldi—43, 81100 Caserta, Italy; (V.R.); (R.M.); (P.V.P.)
- Correspondence: (G.G.); (I.B.); Tel.: +39-081-7865201 (G.G.); +39-0823-274598 (I.B.)
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19
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Salmonella expresses foreign genes during infection by degrading their silencer. Proc Natl Acad Sci U S A 2020; 117:8074-8082. [PMID: 32209674 DOI: 10.1073/pnas.1912808117] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The heat-stable nucleoid structuring (H-NS, also referred to as histone-like nucleoid structuring) protein silences transcription of foreign genes in a variety of Gram-negative bacterial species. To take advantage of the products encoded in foreign genes, bacteria must overcome the silencing effects of H-NS. Because H-NS amounts are believed to remain constant, overcoming gene silencing has largely been ascribed to proteins that outcompete H-NS for binding to AT-rich foreign DNA. However, we report here that the facultative intracellular pathogen Salmonella enterica serovar Typhimurium decreases H-NS amounts 16-fold when inside macrophages. This decrease requires both the protease Lon and the DNA-binding virulence regulator PhoP. The decrease in H-NS abundance reduces H-NS binding to foreign DNA, allowing transcription of foreign genes, including those required for intramacrophage survival. The purified Lon protease degraded free H-NS but not DNA-bound H-NS. By displacing H-NS from DNA, the PhoP protein promoted H-NS proteolysis, thereby de-repressing foreign genes-even those whose regulatory sequences are not bound by PhoP. The uncovered mechanism enables a pathogen to express foreign virulence genes during infection without the need to evolve binding sites for antisilencing proteins at each foreign gene.
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20
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Qin L, Bdira FB, Sterckx YGJ, Volkov AN, Vreede J, Giachin G, van Schaik P, Ubbink M, Dame RT. Structural basis for osmotic regulation of the DNA binding properties of H-NS proteins. Nucleic Acids Res 2020; 48:2156-2172. [PMID: 31925429 PMCID: PMC7039000 DOI: 10.1093/nar/gkz1226] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 11/29/2019] [Accepted: 12/19/2019] [Indexed: 01/07/2023] Open
Abstract
H-NS proteins act as osmotic sensors translating changes in osmolarity into altered DNA binding properties, thus, regulating enterobacterial genome organization and genes transcription. The molecular mechanism underlying the switching process and its conservation among H-NS family members remains elusive. Here, we focus on the H-NS family protein MvaT from Pseudomonas aeruginosa and demonstrate experimentally that its protomer exists in two different conformations, corresponding to two different functional states. In the half-opened state (dominant at low salt) the protein forms filaments along DNA, in the fully opened state (dominant at high salt) the protein bridges DNA. This switching is a direct effect of ionic strength on electrostatic interactions between the oppositely charged DNA binding and N-terminal domains of MvaT. The asymmetric charge distribution and intramolecular interactions are conserved among the H-NS family of proteins. Therefore, our study establishes a general paradigm for the molecular mechanistic basis of the osmosensitivity of H-NS proteins.
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Affiliation(s)
- Liang Qin
- Department of Macromolecular Biochemistry, Leiden Institute of Chemistry, Einsteinweg 55, 2333 CC Leiden, the Netherlands.,Centre for Microbial Cell Biology, Leiden University, Einsteinweg 55, 2333CC Leiden, the Netherlands
| | - Fredj Ben Bdira
- Department of Macromolecular Biochemistry, Leiden Institute of Chemistry, Einsteinweg 55, 2333 CC Leiden, the Netherlands.,Centre for Microbial Cell Biology, Leiden University, Einsteinweg 55, 2333CC Leiden, the Netherlands
| | - Yann G J Sterckx
- Laboratory of Medical Biochemistry, University of Antwerp, Campus Drie Eiken, University Square 1, 2610 Wilrijk, Belgium
| | - Alexander N Volkov
- VIB-VUB Structural Biology Research Center, Pleinlaan 2, 1050 Brussels, Belgium.,Jean Jeener NMR Centre, VUB, Pleinlaan 2, 1050 Brussels, Belgium
| | - Jocelyne Vreede
- Department of Computational Chemistry, Van't Hoff Institute for Molecular Sciences, University of Amsterdam Science Park 904, 1098 XH Amsterdam, the Netherlands
| | - Gabriele Giachin
- Structural Biology Group, European Synchrotron Radiation Facility (ESRF), Grenoble, France
| | - Peter van Schaik
- Department of Macromolecular Biochemistry, Leiden Institute of Chemistry, Einsteinweg 55, 2333 CC Leiden, the Netherlands.,Centre for Microbial Cell Biology, Leiden University, Einsteinweg 55, 2333CC Leiden, the Netherlands
| | - Marcellus Ubbink
- Department of Macromolecular Biochemistry, Leiden Institute of Chemistry, Einsteinweg 55, 2333 CC Leiden, the Netherlands
| | - Remus T Dame
- Department of Macromolecular Biochemistry, Leiden Institute of Chemistry, Einsteinweg 55, 2333 CC Leiden, the Netherlands.,Centre for Microbial Cell Biology, Leiden University, Einsteinweg 55, 2333CC Leiden, the Netherlands
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21
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Crisan CV, Hammer BK. The
Vibrio cholerae
type VI secretion system: toxins, regulators and consequences. Environ Microbiol 2020; 22:4112-4122. [DOI: 10.1111/1462-2920.14976] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 03/01/2020] [Accepted: 03/02/2020] [Indexed: 12/13/2022]
Affiliation(s)
- Cristian V. Crisan
- Center for Microbial Dynamics and Infection Georgia Institute of Technology Atlanta GA USA
- Institute for Bioengineering and Biosciences, Georgia Institute of Technology Atlanta GA USA
- School of Biological Sciences, Georgia Institute of Technology Atlanta GA USA
| | - Brian K. Hammer
- Center for Microbial Dynamics and Infection Georgia Institute of Technology Atlanta GA USA
- Institute for Bioengineering and Biosciences, Georgia Institute of Technology Atlanta GA USA
- School of Biological Sciences, Georgia Institute of Technology Atlanta GA USA
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22
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Qin L, Erkelens AM, Ben Bdira F, Dame RT. The architects of bacterial DNA bridges: a structurally and functionally conserved family of proteins. Open Biol 2019; 9:190223. [PMID: 31795918 PMCID: PMC6936261 DOI: 10.1098/rsob.190223] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Accepted: 11/08/2019] [Indexed: 12/15/2022] Open
Abstract
Every organism across the tree of life compacts and organizes its genome with architectural chromatin proteins. While eukaryotes and archaea express histone proteins, the organization of bacterial chromosomes is dependent on nucleoid-associated proteins. In Escherichia coli and other proteobacteria, the histone-like nucleoid structuring protein (H-NS) acts as a global genome organizer and gene regulator. Functional analogues of H-NS have been found in other bacterial species: MvaT in Pseudomonas species, Lsr2 in actinomycetes and Rok in Bacillus species. These proteins complement hns- phenotypes and have similar DNA-binding properties, despite their lack of sequence homology. In this review, we focus on the structural and functional characteristics of these four architectural proteins. They are able to bridge DNA duplexes, which is key to genome compaction, gene regulation and their response to changing conditions in the environment. Structurally the domain organization and charge distribution of these proteins are conserved, which we suggest is at the basis of their conserved environment responsive behaviour. These observations could be used to find and validate new members of this protein family and to predict their response to environmental changes.
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Affiliation(s)
- L. Qin
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333CC Leiden, The Netherlands
- Centre for Microbial Cell Biology, Leiden University, Leiden, The Netherlands
| | - A. M. Erkelens
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333CC Leiden, The Netherlands
- Centre for Microbial Cell Biology, Leiden University, Leiden, The Netherlands
| | - F. Ben Bdira
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333CC Leiden, The Netherlands
- Centre for Microbial Cell Biology, Leiden University, Leiden, The Netherlands
| | - R. T. Dame
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333CC Leiden, The Netherlands
- Centre for Microbial Cell Biology, Leiden University, Leiden, The Netherlands
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23
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Hsieh PF, Lu YR, Lin TL, Lai LY, Wang JT. Klebsiella pneumoniae Type VI Secretion System Contributes to Bacterial Competition, Cell Invasion, Type-1 Fimbriae Expression, and In Vivo Colonization. J Infect Dis 2019; 219:637-647. [PMID: 30202982 PMCID: PMC6350951 DOI: 10.1093/infdis/jiy534] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Accepted: 09/03/2018] [Indexed: 01/25/2023] Open
Abstract
Background We previously isolated a Klebsiella pneumoniae strain, NTUH-K2044, from a community-acquired pyogenic liver abscess (PLA) patient. Analysis of the NTUH-K2044 genome revealed that this strain harbors 2 putative type VI secretion system (T6SS)-encoding gene clusters. Methods The distribution of T6SS genes in the PLA and intestinal-colonizing K pneumoniae clinical isolates was examined. icmF1-, icmF2-, icmF1/icmF2-, and hcp-deficient K pneumoniae strains were constructed using an unmarked deletion method. The roles of T6SSs in antibacterial activity, type-1 fimbriae expression, cell adhesion, and invasion and intestinal colonization were determined. Results The prevalence of T6SSs is higher in the PLA strains than in the intestinal-colonizing strains (37 of 42 vs 54 of 130). Deletion of icmF1/icmF2 and hcp genes significantly reduced interbacterial and intrabacterial killing. Strain deleted for icmF1 and icmF2 exhibited decreased transcriptional expression of type-1 fimbriae and reduced adherence to and invasion of human colorectal epithelial cells and was attenuated for in vivo competition to enable colonization of the host gut. Finally, Hcp expression in K pneumoniae was silenced by the histone-like nucleoid structuring protein via direct binding. Conclusions These results provide new insights into T6SS-mediated bacterial competition and attachment in K pneumoniae and could facilitate the prevention of K pneumoniae infection.
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Affiliation(s)
- Pei-Fang Hsieh
- Department of Microbiology, National Taiwan University College of Medicine, Taipei
| | - Yi-Rou Lu
- Department of Microbiology, National Taiwan University College of Medicine, Taipei
| | - Tzu-Lung Lin
- Department of Microbiology, National Taiwan University College of Medicine, Taipei
| | - Li-Yin Lai
- Department of Microbiology, National Taiwan University College of Medicine, Taipei
| | - Jin-Town Wang
- Department of Microbiology, National Taiwan University College of Medicine, Taipei.,Department of Internal Medicine, National Taiwan University Hospital, Taipei
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24
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Belibasakis GN, Maula T, Bao K, Lindholm M, Bostanci N, Oscarsson J, Ihalin R, Johansson A. Virulence and Pathogenicity Properties of Aggregatibacter actinomycetemcomitans. Pathogens 2019; 8:E222. [PMID: 31698835 PMCID: PMC6963787 DOI: 10.3390/pathogens8040222] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 10/29/2019] [Accepted: 11/04/2019] [Indexed: 02/06/2023] Open
Abstract
Aggregatibacter actinomycetemcomitans is a periodontal pathogen colonizing the oral cavity of a large proportion of the human population. It is equipped with several potent virulence factors that can cause cell death and induce or evade inflammation. Because of the large genetic diversity within the species, both harmless and highly virulent genotypes of the bacterium have emerged. The oral condition and age, as well as the geographic origin of the individual, influence the risk to be colonized by a virulent genotype of the bacterium. In the present review, the virulence and pathogenicity properties of A. actinomycetemcomitans will be addressed.
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Affiliation(s)
- Georgios N. Belibasakis
- Division of Oral Diseases, Department of Dental Medicine, Karolinska Institutet, S-141 04 Huddinge, Sweden; (G.N.B.); (K.B.); (N.B.)
| | - Terhi Maula
- Department of Biochemistry, University of Turku, FI-20014 Turku, Finland; (T.M.); (R.I.)
| | - Kai Bao
- Division of Oral Diseases, Department of Dental Medicine, Karolinska Institutet, S-141 04 Huddinge, Sweden; (G.N.B.); (K.B.); (N.B.)
| | - Mark Lindholm
- Department of Odontology, Umeå University, S-901 87 Umeå, Sweden; (M.L.); (J.O.)
| | - Nagihan Bostanci
- Division of Oral Diseases, Department of Dental Medicine, Karolinska Institutet, S-141 04 Huddinge, Sweden; (G.N.B.); (K.B.); (N.B.)
| | - Jan Oscarsson
- Department of Odontology, Umeå University, S-901 87 Umeå, Sweden; (M.L.); (J.O.)
| | - Riikka Ihalin
- Department of Biochemistry, University of Turku, FI-20014 Turku, Finland; (T.M.); (R.I.)
| | - Anders Johansson
- Department of Odontology, Umeå University, S-901 87 Umeå, Sweden; (M.L.); (J.O.)
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25
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Shen BA, Landick R. Transcription of Bacterial Chromatin. J Mol Biol 2019; 431:4040-4066. [PMID: 31153903 PMCID: PMC7248592 DOI: 10.1016/j.jmb.2019.05.041] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 05/22/2019] [Accepted: 05/23/2019] [Indexed: 12/12/2022]
Abstract
Decades of research have probed the interplay between chromatin (genomic DNA associated with proteins and RNAs) and transcription by RNA polymerase (RNAP) in all domains of life. In bacteria, chromatin is compacted into a membrane-free region known as the nucleoid that changes shape and composition depending on the bacterial state. Transcription plays a key role in both shaping the nucleoid and organizing it into domains. At the same time, chromatin impacts transcription by at least five distinct mechanisms: (i) occlusion of RNAP binding; (ii) roadblocking RNAP progression; (iii) constraining DNA topology; (iv) RNA-mediated interactions; and (v) macromolecular demixing and heterogeneity, which may generate phase-separated condensates. These mechanisms are not mutually exclusive and, in combination, mediate gene regulation. Here, we review the current understanding of these mechanisms with a focus on gene silencing by H-NS, transcription coordination by HU, and potential phase separation by Dps. The myriad questions about transcription of bacterial chromatin are increasingly answerable due to methodological advances, enabling a needed paradigm shift in the field of bacterial transcription to focus on regulation of genes in their native state. We can anticipate answers that will define how bacterial chromatin helps coordinate and dynamically regulate gene expression in changing environments.
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Affiliation(s)
- Beth A Shen
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, United States
| | - Robert Landick
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, United States; Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, United States.
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26
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Gulvady R, Gao Y, Kenney LJ, Yan J. A single molecule analysis of H-NS uncouples DNA binding affinity from DNA specificity. Nucleic Acids Res 2019; 46:10216-10224. [PMID: 30239908 PMCID: PMC6212787 DOI: 10.1093/nar/gky826] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2018] [Accepted: 09/06/2018] [Indexed: 12/29/2022] Open
Abstract
Heat-stable nucleoid structuring protein (H-NS) plays a crucial role in gene silencing within prokaryotic cells and is important in pathogenesis. It was reported that H-NS silences nearly 5% of the genome, yet the molecular mechanism of silencing is not well understood. Here, we employed a highly-sensitive single-molecule counting approach, and measured the dissociation constant (KD) of H-NS binding to single DNA binding sites. Charged residues in the linker domain of H-NS provided the most significant contribution to DNA binding affinity. Although H-NS was reported to prefer A/T-rich DNA (a feature of pathogenicity islands) over G/C-rich DNA, the dissociation constants obtained from such sites were nearly identical. Using a hairpin unzipping assay, we were able to uncouple non-specific DNA binding steps from nucleation site binding and subsequent polymerization. We propose a model in which H-NS initially engages with non-specific DNA via reasonably high affinity (∼60 nM KD) electrostatic interactions with basic residues in the linker domain. This initial contact enables H-NS to search along the DNA for specific nucleation sites that drive subsequent polymerization and gene silencing.
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Affiliation(s)
- Ranjit Gulvady
- Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore
| | - Yunfeng Gao
- Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore
| | - Linda J Kenney
- Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore.,Jesse Brown Veterans Administration Medical Center, Chicago, IL 6061, USA.,Department of Microbiology and Immunology, University of Illinois-Chicago, Chicago, IL 60612, USA.,Department of Biochemistry, National University of Singapore, Singapore 117596, Singapore
| | - Jie Yan
- Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore.,Department of Physics, National University of Singapore, Singapore 117542, Singapore.,Centre for Bioimaging Sciences, National University of Singapore, Singapore 117546, Singapore
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27
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Identifying the region responsible for Brucella abortus MucR higher-order oligomer formation and examining its role in gene regulation. Sci Rep 2018; 8:17238. [PMID: 30467359 PMCID: PMC6250670 DOI: 10.1038/s41598-018-35432-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Accepted: 11/05/2018] [Indexed: 11/09/2022] Open
Abstract
MucR is a member of the Ros/MucR family of prokaryotic zinc-finger proteins found in the α-proteobacteria which regulate the expression of genes required for the successful pathogenic and symbiotic interactions of these bacteria with the eukaryotic hosts. The structure and function of their distinctive zinc-finger domain has been well-studied, but only recently the quaternary structure of the full length proteins was investigated demonstrating their ability to form higher-order oligomers. The aim of this study was to identify the region of MucR involved in higher-order oligomer formation by analysing deletion and point mutants of this protein by Light Scattering, and to determine the role that MucR oligomerization plays in the regulatory function of this protein. Here we demonstrate that a conserved hydrophobic region at the N-terminus of MucR is responsible for higher-order oligomer formation and that MucR oligomerization is essential for its regulatory function in Brucella. All these features of MucR are shared by the histone-like nucleoid structuring protein, (H-NS), leading us to propose that the prokaryotic zinc-finger proteins in the MucR/Ros family control gene expression employing a mechanism similar to that used by the H-NS proteins, rather than working as classical transcriptional regulators.
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28
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Boudreau BA, Hron DR, Qin L, van der Valk RA, Kotlajich MV, Dame RT, Landick R. StpA and Hha stimulate pausing by RNA polymerase by promoting DNA-DNA bridging of H-NS filaments. Nucleic Acids Res 2018; 46:5525-5546. [PMID: 29718386 PMCID: PMC6009659 DOI: 10.1093/nar/gky265] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Revised: 03/12/2018] [Accepted: 04/03/2018] [Indexed: 11/22/2022] Open
Abstract
In enterobacteria, AT-rich horizontally acquired genes, including virulence genes, are silenced through the actions of at least three nucleoid-associated proteins (NAPs): H-NS, StpA and Hha. These proteins form gene-silencing nucleoprotein filaments through direct DNA binding by H-NS and StpA homodimers or heterodimers. Both linear and bridged filaments, in which NAPs bind one or two DNA segments, respectively, have been observed. Hha can interact with H-NS or StpA filaments, but itself lacks a DNA-binding domain. Filaments composed of H-NS alone can inhibit transcription initiation and, in the bridged conformation, slow elongating RNA polymerase (RNAP) by promoting backtracking at pause sites. How the other NAPs modulate these effects of H-NS is unknown, despite evidence that they help regulate subsets of silenced genes in vivo (e.g. in pathogenicity islands). Here we report that Hha and StpA greatly enhance H-NS-stimulated pausing by RNAP at 20°C. StpA:H-NS or StpA-only filaments also stimulate pausing at 37°C, a temperature at which Hha:H-NS or H-NS-only filaments have much less effect. In addition, we report that both Hha and StpA greatly stimulate DNA-DNA bridging by H-NS filaments. Together, these observations indicate that Hha and StpA can affect H-NS-mediated gene regulation by stimulating bridging of H-NS/DNA filaments.
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Affiliation(s)
- Beth A Boudreau
- Department of Biochemistry, University of Wisconsin–Madison, Madison, WI 53706, USA
| | - Daniel R Hron
- Department of Biochemistry, University of Wisconsin–Madison, Madison, WI 53706, USA
| | - Liang Qin
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333 CC, Leiden, Netherlands
| | - Ramon A van der Valk
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333 CC, Leiden, Netherlands
| | - Matthew V Kotlajich
- Department of Biochemistry, University of Wisconsin–Madison, Madison, WI 53706, USA
| | - Remus T Dame
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333 CC, Leiden, Netherlands
| | - Robert Landick
- Department of Biochemistry, University of Wisconsin–Madison, Madison, WI 53706, USA
- Department of Bacteriology, University of Wisconsin–Madison, Madison, WI 53706, USA
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29
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Bao K, Bostanci N, Thurnheer T, Grossmann J, Wolski WE, Thay B, Belibasakis GN, Oscarsson J. Aggregatibacter actinomycetemcomitans H-NS promotes biofilm formation and alters protein dynamics of other species within a polymicrobial oral biofilm. NPJ Biofilms Microbiomes 2018; 4:12. [PMID: 29844920 PMCID: PMC5964231 DOI: 10.1038/s41522-018-0055-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Revised: 04/03/2018] [Accepted: 04/19/2018] [Indexed: 12/12/2022] Open
Abstract
Aggregatibacter actinomycetemcomitans is a Gram-negative organism, strongly associated with aggressive forms of periodontitis. An important virulence property of A. actinomycetemcomitans is its ability to form tenacious biofilms that can attach to abiotic as well as biotic surfaces. The histone-like (H-NS) family of nucleoid-structuring proteins act as transcriptional silencers in many Gram-negative bacteria. To evaluate the role of H-NS in A. actinomycetemcomitans, hns mutant derivatives of serotype a strain D7S were generated. Characteristics of the hns mutant phenotype included shorter and fewer pili, and substantially lower monospecies biofilm formation relative to the wild type. Furthermore, the D7S hns mutant exhibited significantly reduced growth within a seven-species oral biofilm model. However, no apparent difference was observed regarding the numbers and proportions of the remaining six species regardless of being co-cultivated with D7S hns or its parental strain. Proteomics analysis of the strains grown in monocultures confirmed the role of H-NS as a repressor of gene expression in A. actinomycetemcomitans. Interestingly, proteomics analysis of the multispecies biofilms indicated that the A. actinomycetemcomitans wild type and hns mutant imposed different regulatory effects on the pattern of protein expression in the other species, i.e., mainly Streptococcus spp., Fusobacterium nucleatum, and Veillonella dispar. Gene ontology analysis revealed that a large portion of the differentially regulated proteins was related to translational activity. Taken together, our data suggest that, apart from being a negative regulator of protein expression in A. actinomycetemcomitans, H-NS promotes biofilm formation and may be an important factor for survival of this species within a multispecies biofilm. A member of a specific group of gene-regulating proteins promotes biofilm formation by a bacterium associated with aggressive forms of gum disease. Forming biofilms helps the bacterium to cause persistent infections. Researchers at Karolinska Institutet and Umeå University (Sweden), and University of Zürich (Switzerland), led by Jan Oscarsson at Umeå University, investigated the role of the “histone-like” protein H-NS in Aggregatibacter actinomycetemcomitans infections. These proteins are known to suppress the activity of specific genes in many bacteria, a property confirmed in this research. By studying mutant bacterial strains deficient in H-NS protein, the researchers demonstrated that this protein promotes the formation of biofilms by the bacteria. The results suggest that H-NS plays a significant role in allowing Aggregatibacter actinomycetemcomitans to thrive in biofilms containing mixed populations of bacteria. This effect appears to involve activating production of hair-like appendages called pili on the bacterial surface.
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Affiliation(s)
- Kai Bao
- 1Division of Oral Diseases, Department of Dental Medicine, Karolinska Institutet, Huddinge, Solnavägen, Sweden.,2Division of Oral Microbiology and Immunology, Center of Dental Medicine, University of Zürich, Zürich, Switzerland
| | - Nagihan Bostanci
- 1Division of Oral Diseases, Department of Dental Medicine, Karolinska Institutet, Huddinge, Solnavägen, Sweden
| | - Thomas Thurnheer
- 2Division of Oral Microbiology and Immunology, Center of Dental Medicine, University of Zürich, Zürich, Switzerland
| | - Jonas Grossmann
- 3Functional Genomics Center, ETH Zürich and University of Zürich, Zürich, Switzerland
| | - Witold E Wolski
- 3Functional Genomics Center, ETH Zürich and University of Zürich, Zürich, Switzerland
| | - Bernard Thay
- 4Oral Microbiology, Department of Odontology, Umeå University, Umeå, Sweden
| | - Georgios N Belibasakis
- 1Division of Oral Diseases, Department of Dental Medicine, Karolinska Institutet, Huddinge, Solnavägen, Sweden
| | - Jan Oscarsson
- 4Oral Microbiology, Department of Odontology, Umeå University, Umeå, Sweden
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30
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Baglivo I, Pirone L, Malgieri G, Fattorusso R, Roop II RM, Pedone EM, Pedone PV. MucR binds multiple target sites in the promoter of its own gene and is a heat-stable protein: Is MucR a H-NS-like protein? FEBS Open Bio 2018; 8:711-718. [PMID: 29632823 PMCID: PMC5881533 DOI: 10.1002/2211-5463.12411] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2018] [Revised: 02/17/2018] [Accepted: 02/21/2018] [Indexed: 01/08/2023] Open
Abstract
The protein MucR from Brucella spp. is involved in the expression regulation of genes necessary for host interaction and infection. MucR is a member of the Ros/MucR family, which comprises prokaryotic zinc-finger proteins and includes Ros from Agrobacterium tumefaciens and the Ml proteins from Mesorhizobium loti. MucR from Brucella spp. can regulate the expression of virulence genes and repress its own gene expression. Despite the well-known role played by MucR in the repression of its own gene, no target sequence has yet been identified in the mucR promoter gene. In this study, we provide the first evidence that MucR from Brucella abortus binds more than one target site in the promoter region of its own gene, suggesting a molecular mechanism by which this protein represses its own expression. Furthermore, a circular dichroism analysis reveals that MucR is a heat-stable protein. Overall, the results of this study suggest that MucR might resemble a H-NS protein.
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Affiliation(s)
- Ilaria Baglivo
- Department of Environmental, Biological and Pharmaceutical Sciences and TechnologiesUniversity of Campania ‘Luigi Vanvitelli’CasertaItaly
| | - Luciano Pirone
- Institute of Biostructures and BioimagingC.N.R.NaplesItaly
| | - Gaetano Malgieri
- Department of Environmental, Biological and Pharmaceutical Sciences and TechnologiesUniversity of Campania ‘Luigi Vanvitelli’CasertaItaly
| | - Roberto Fattorusso
- Department of Environmental, Biological and Pharmaceutical Sciences and TechnologiesUniversity of Campania ‘Luigi Vanvitelli’CasertaItaly
| | - Roy Martin Roop II
- Department of Microbiology and ImmunologyBrody School of MedicineEast Carolina UniversityGreenvilleNCUSA
| | | | - Paolo Vincenzo Pedone
- Department of Environmental, Biological and Pharmaceutical Sciences and TechnologiesUniversity of Campania ‘Luigi Vanvitelli’CasertaItaly
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31
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Santiago AE, Yan MB, Hazen TH, Sauder B, Meza-Segura M, Rasko DA, Kendall MM, Ruiz-Perez F, Nataro JP. The AraC Negative Regulator family modulates the activity of histone-like proteins in pathogenic bacteria. PLoS Pathog 2017; 13:e1006545. [PMID: 28806780 PMCID: PMC5570504 DOI: 10.1371/journal.ppat.1006545] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Revised: 08/24/2017] [Accepted: 07/20/2017] [Indexed: 02/04/2023] Open
Abstract
The AraC Negative Regulators (ANR) comprise a large family of virulence regulators distributed among diverse clinically important Gram-negative pathogens, including Vibrio spp., Salmonella spp., Shigella spp., Yersinia spp., Citrobacter spp., and pathogenic E. coli strains. We have previously reported broad effects of the ANR members on regulators of the AraC/XylS family. Here, we interrogate possible broader effects of the ANR members on the bacterial transcriptome. Our studies focused on Aar (AggR-activated regulator), an ANR family archetype in enteroaggregative E. coli (EAEC) isolate 042. Transcriptome analysis of EAEC strain 042, 042aar and 042aar(pAar) identified more than 200 genes that were differentially expressed (+/- 1.5 fold, p<0.05). Most of those genes are located on the bacterial chromosome (195 genes, 92.85%), and are associated with regulation, transport, metabolism, and pathogenesis, based on the predicted annotation; a considerable number of Aar-regulated genes encoded for hypothetical proteins (46 genes, 21.9%) and regulatory proteins (25, 11.9%). Notably, the transcriptional expression of three histone-like regulators, H-NS (orf1292), H-NS homolog (orf2834) and StpA, was down-regulated in the absence of aar and may explain some of the effects of Aar on gene expression. By employing a bacterial two-hybrid system, LacZ reporter assays, pull-down and electrophoretic mobility shift assay (EMSA) analysis, we demonstrated that Aar binds directly to H-NS and modulates H-NS-induced gene silencing. Importantly, Aar was highly expressed in the mouse intestinal tract and was found to be necessary for maximal H-NS expression. In conclusion, this work further extends our knowledge of genes under the control of Aar and its biological relevance in vivo. The AraC Negative Regulators (ANR) is a large family of negative regulators distributed in several clinically relevant Gram-negative pathogens, including Vibrio spp., Salmonella spp., Shigella spp., Yersinia spp., Citrobacter spp., pathogenic E. coli, and members of the Pasteurellaceae. Previously, we showed that the ANR family suppresses transcriptional expression of virulence factors such as fimbriae, toxins, and the type VI secretion system by directly down-regulating AraC/XylS master regulators. Transcriptome and biochemical analysis of Aar (AggR-activated regulator), an ANR family archetype in enteroaggregative E. coli (EAEC) 042, demonstrated that Aar binds directly to H-NS and modulates the H-NS-induced gene expression. Accordingly, mutation of aar decreased expression of the H-NS-regulated Lpf fimbriae, LPS-related enzymes, GadXW operon and porins. Importantly, Aar was highly expressed in the mouse intestinal tract and was found to be necessary for maximal H-NS expression. These findings unveil an exquisite regulatory network in pathogenic bacteria, which operates by concomitant control of master transcriptional regulators of the AraC family and global negative H-NS regulators.
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Affiliation(s)
- Araceli E. Santiago
- Department of Pediatrics, University of Virginia School of Medicine, Charlottesville, Virginia, United States of America
- * E-mail:
| | - Michael B. Yan
- Department of Pediatrics, University of Virginia School of Medicine, Charlottesville, Virginia, United States of America
| | - Tracy H. Hazen
- Institute for Genome Sciences, Department of Microbiology and Immunology. University of Maryland, Baltimore, Maryland, United States of America
| | - Brooke Sauder
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, Virginia, United States of America
| | - Mario Meza-Segura
- Department of Pediatrics, University of Virginia School of Medicine, Charlottesville, Virginia, United States of America
| | - David A. Rasko
- Institute for Genome Sciences, Department of Microbiology and Immunology. University of Maryland, Baltimore, Maryland, United States of America
| | - Melissa M. Kendall
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, Virginia, United States of America
| | - Fernando Ruiz-Perez
- Department of Pediatrics, University of Virginia School of Medicine, Charlottesville, Virginia, United States of America
| | - James P. Nataro
- Department of Pediatrics, University of Virginia School of Medicine, Charlottesville, Virginia, United States of America
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Additional regulatory activities of MrkH for the transcriptional expression of the Klebsiella pneumoniae mrk genes: Antagonist of H-NS and repressor. PLoS One 2017; 12:e0173285. [PMID: 28278272 PMCID: PMC5344390 DOI: 10.1371/journal.pone.0173285] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Accepted: 02/07/2017] [Indexed: 11/19/2022] Open
Abstract
Klebsiella pneumoniae is a common opportunistic pathogen causing nosocomial infections. One of the main virulence determinants of K. pneumoniae is the type 3 pilus (T3P). T3P helps the bacterial interaction to both abiotic and biotic surfaces and it is crucial for the biofilm formation. T3P is genetically organized in three transcriptional units: the mrkABCDF polycistronic operon, the mrkHI bicistronic operon and the mrkJ gene. MrkH is a regulatory protein encoded in the mrkHI operon, which positively regulates the mrkA pilin gene and its own expression. In contrast, the H-NS nucleoid protein represses the transcriptional expression of T3P. Here we reported that MrkH and H-NS positively and negatively regulate mrkJ expression, respectively, by binding to the promoter of mrkJ. MrkH protein recognized a sequence located at position -63.5 relative to the transcriptional start site of mrkJ gene. Interestingly, our results show that, in addition to its known function as classic transcriptional activator, MrkH also positively controls the expression of mrk genes by acting as an anti-repressor of H-NS; moreover, our results support the notion that high levels of MrkH repress T3P expression. Our data provide new insights about the complex regulatory role of the MrkH protein on the transcriptional control of T3P in K. pneumoniae.
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H-NS, Its Family Members and Their Regulation of Virulence Genes in Shigella Species. Genes (Basel) 2016; 7:genes7120112. [PMID: 27916940 PMCID: PMC5192488 DOI: 10.3390/genes7120112] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Revised: 11/22/2016] [Accepted: 11/24/2016] [Indexed: 12/04/2022] Open
Abstract
The histone-like nucleoid structuring protein (H-NS) has played a key role in shaping the evolution of Shigella spp., and provides the backdrop to the regulatory cascade that controls virulence by silencing many genes found on the large virulence plasmid. H-NS and its paralogue StpA are present in all four Shigella spp., but a second H-NS paralogue, Sfh, is found in the Shigella flexneri type strain 2457T, which is routinely used in studies of Shigella pathogenesis. While StpA and Sfh have been proposed to serve as “molecular backups” for H-NS, the apparent redundancy of these proteins is questioned by in vitro studies and work done in Escherichia coli. In this review, we describe the current understanding of the regulatory activities of the H-NS family members, the challenges associated with studying these proteins and their role in the regulation of virulence genes in Shigella.
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Elgaml A, Miyoshi SI. Role of the Histone-Like Nucleoid Structuring Protein (H-NS) in the Regulation of Virulence Factor Expression and Stress Response in Vibrio vulnificus. Biocontrol Sci 2016; 20:263-74. [PMID: 26699858 DOI: 10.4265/bio.20.263] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
Abstract
Temperature is one of the important parameters regulating the expression of virulence factors in bacteria. The global regulator, a histone-like nucleoid structuring protein (H-NS), is known to play a crucial role in this regulation. In the present study, we first clarified the role of H-NS in the temperature-dependent regulation of virulence factor production in Vibrio vulnificus, including that of the cytolytic toxin (V. vulnificus hemolysin: VVH) and the proteolytic enzyme (V. vulnificus protease: VVP). The expression of hns itself was subjected to temperature regulation, where hns was expressed more at 26 ℃ than at 37 ℃. VVH production and the expression of its gene vvhA were increased by disruption of the hns gene. H-NS appeared to affect the vvhA expression by the well-documented transcriptional silencing mechanism. On the other hand, hns disruption resulted in the reduction of VVP production and the expression of its gene vvpE. H-NS was suggested to positively regulate vvpE expression through the increase in the level of the rpoS mRNA. Moreover, H-NS was found to contribute to the survival of V. vulnificus in stressful environments. When compared to the wild type strain, the hns mutant exhibited reduced survival rates when subjected to acidic pH, hyperosmotic and oxidative stress.
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Affiliation(s)
- Abdelaziz Elgaml
- Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University
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Cui S, Xiao J, Wang Q, Zhang Y. H-NS binding to evpB and evpC and repressing T6SS expression in fish pathogen Edwardsiella piscicida. Arch Microbiol 2016; 198:653-61. [PMID: 27125651 DOI: 10.1007/s00203-016-1226-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2015] [Revised: 03/11/2016] [Accepted: 04/15/2016] [Indexed: 11/30/2022]
Abstract
Edwardsiella piscicida is an important causative agent of hemorrhagic septicemia in fish and infects both cultured and wild fish species. Type VI secretion system (T6SS) was proved to play important roles in pathogenesis of E. piscicida. In this study, it was demonstrated that the expression of T6SS genes evpB and evpC was under control of the global regulator H-NS in E. piscicida and the transcriptional level of evpB and evpC was significantly down-regulated by H-NS. Compared to the wild type, the transcriptional levels of evpB and evpC were up-regulated in hns null mutant, while down-regulated in hns overexpression strain. The results of EMSA and DNase I footprinting revealed that H-NS protein directly bound to upstream region of evpC at multiple sites. A high-affinity motif with a 9-nucleotide sequence 5'-ATATAAAAT-3' was defined for H-NS preferential recognition based on the feature of the binding sites. These results indicated that H-NS acted cooperatively to form extended nucleoprotein filaments on target DNA. Site-directed mutagenesis of H-NS further showed that R86 played an essential role in T6SS gene binding. These findings highlighted the mechanisms underlying the complex regulation network of T6SS by H-NS in E. piscicida.
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Affiliation(s)
- Shilei Cui
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, 200237, China
| | - Jingfan Xiao
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, 200237, China. .,Shanghai Engineering Research Center of Maricultured Animal Vaccines, Shanghai, China.
| | - Qiyao Wang
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, 200237, China.,Shanghai Engineering Research Center of Maricultured Animal Vaccines, Shanghai, China.,Shanghai Collaborative Innovation Center for Biomanufacturing Technology, Shanghai, China
| | - Yuanxing Zhang
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, 200237, China.,Shanghai Engineering Research Center of Maricultured Animal Vaccines, Shanghai, China.,Shanghai Collaborative Innovation Center for Biomanufacturing Technology, Shanghai, China
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The Histone-Like Nucleoid Structuring Protein (H-NS) Is a Negative Regulator of the Lateral Flagellar System in the Deep-Sea Bacterium Shewanella piezotolerans WP3. Appl Environ Microbiol 2016; 82:2388-2398. [PMID: 26873312 DOI: 10.1128/aem.00297-16] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Accepted: 02/05/2016] [Indexed: 11/20/2022] Open
Abstract
Although the histone-like nucleoid structuring protein (H-NS) is well known for its involvement in the adaptation of mesophilic bacteria, such as Escherichia coli, to cold environments and high-pressure stress, an understanding of the role of H-NS in the cold-adapted benthic microorganisms that live in the deep-sea ecosystem, which covers approximately 60% of the earth's surface, is still lacking. In this study, we characterized the function of H-NS in Shewanella piezotolerans WP3, which was isolated from West Pacific sediment at a depth of 1,914 m. Anhns gene deletion mutant (WP3Δhns) was constructed, and comparative whole-genome microarray analysis was performed. H-NS had a significant influence (fold change, >2) on the expression of a variety of WP3 genes (274 and 280 genes were upregulated and downregulated, respectively), particularly genes related to energy production and conversion. Notably, WP3Δhnsexhibited higher expression levels of lateral flagellar genes than WP3 and showed enhanced swarming motility and lateral flagellar production compared to those of WP3. The DNA gel mobility shift experiment showed that H-NS bound specifically to the promoter of lateral flagellar genes. Moreover, the high-affinity binding sequences of H-NS were identified by DNase I protection footprinting, and the results support the "binding and spreading" model for H-NS functioning. To our knowledge, this is the first attempt to characterize the function of the universal regulator H-NS in a deep-sea bacterium. Our data revealed that H-NS has a novel function as a repressor of the expression of genes related to the energy-consuming secondary flagellar system and to swarming motility.
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Liu Y, Long J, Shen D, Song C. Xanthomonas oryzae pv. oryzae requires H-NS-family protein XrvC to regulate virulence during rice infection. FEMS Microbiol Lett 2016; 363:fnw067. [PMID: 27001973 DOI: 10.1093/femsle/fnw067] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/16/2016] [Indexed: 01/18/2023] Open
Abstract
Histone-like nucleoid-structuring (H-NS) proteins, which are conserved in Gram-negative bacteria, bind DNA and act as the global transcriptional repressors. In this study, we identified and characterized the xrvC gene encoding a H-NS protein in Xathomonas oryzae pv. oryzae (Xoo) Philippines strain PXO99(A) Compared with the wild type, the xrvC-deficient mutant of PXO99(A) (named PXO99ΔxrvC) showed a reduced growth rate in both nutrient-rich and nutrient-limited media. Interestingly, PXO99ΔxrvC exhibited significantly reduced virulence on rice cultivar IRBB214, but its virulence on 31 other rice cultivars was not affected. Transcriptional analysis revealed that the expression of hrpG, hrpX and hpa1 and of 15 out of 18 tested non-TAL (transcription activator-like) effector genes was decreased significantly in the xrvC mutant compared with that in the wild type. In addition, loss of xrvC also impaired the induction of the rice susceptibility gene Os8N3 in IRBB214 by PXO99(A) Our results suggest that the xrvC gene is involved in bacterial growth, and it plays a vital role in virulence by positively regulating the expression of hrp genes and non-TAL effector genes in PXO99(A) and the susceptibility gene Os8N3 in rice.
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Affiliation(s)
- Yongting Liu
- College of Plant Protection/Key Laboratory of Integrated Management of Crop Diseases and Pests, Ministry of Education, Nanjing Agricultural University, Nanjing, China
| | - Juying Long
- College of Plant Protection/Key Laboratory of Integrated Management of Crop Diseases and Pests, Ministry of Education, Nanjing Agricultural University, Nanjing, China
| | - Dan Shen
- College of Plant Protection/Key Laboratory of Integrated Management of Crop Diseases and Pests, Ministry of Education, Nanjing Agricultural University, Nanjing, China
| | - Congfeng Song
- College of Plant Protection/Key Laboratory of Integrated Management of Crop Diseases and Pests, Ministry of Education, Nanjing Agricultural University, Nanjing, China
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Ares MA, Fernández-Vázquez JL, Rosales-Reyes R, Jarillo-Quijada MD, von Bargen K, Torres J, González-y-Merchand JA, Alcántar-Curiel MD, De la Cruz MA. H-NS Nucleoid Protein Controls Virulence Features of Klebsiella pneumoniae by Regulating the Expression of Type 3 Pili and the Capsule Polysaccharide. Front Cell Infect Microbiol 2016; 6:13. [PMID: 26904512 PMCID: PMC4746245 DOI: 10.3389/fcimb.2016.00013] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Accepted: 01/22/2016] [Indexed: 12/14/2022] Open
Abstract
Klebsiella pneumoniae is an opportunistic pathogen causing nosocomial infections. Main virulence determinants of K. pneumoniae are pili, capsular polysaccharide, lipopolysaccharide, and siderophores. The histone-like nucleoid-structuring protein (H-NS) is a pleiotropic regulator found in several gram-negative pathogens. It has functions both as an architectural component of the nucleoid and as a global regulator of gene expression. We generated a Δhns mutant and evaluated the role of the H-NS nucleoid protein on the virulence features of K. pneumoniae. A Δhns mutant down-regulated the mrkA pilin gene and biofilm formation was affected. In contrast, capsule expression was derepressed in the absence of H-NS conferring a hypermucoviscous phenotype. Moreover, H-NS deficiency affected the K. pneumoniae adherence to epithelial cells such as A549 and HeLa cells. In infection experiments using RAW264.7 and THP-1 differentiated macrophages, the Δhns mutant was less phagocytized than the wild-type strain. This phenotype was likely due to the low adherence to these phagocytic cells. Taken together, our data indicate that H-NS nucleoid protein is a crucial regulator of both T3P and CPS of K. pneumoniae.
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Affiliation(s)
- Miguel A Ares
- Unidad de Investigación Médica en Enfermedades Infecciosas y Parasitarias, Hospital de Pediatría, Centro Médico Nacional Siglo XXI, Instituto Mexicano del Seguro Social, Hospital de PediatríaMexico City, Mexico; Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico NacionalMexico City, Mexico
| | - José L Fernández-Vázquez
- Unidad de Investigación en Medicina Experimental, Facultad de Medicina, Universidad Nacional Autónoma de México Mexico City, Mexico
| | - Roberto Rosales-Reyes
- Unidad de Investigación en Medicina Experimental, Facultad de Medicina, Universidad Nacional Autónoma de México Mexico City, Mexico
| | - Ma Dolores Jarillo-Quijada
- Unidad de Investigación en Medicina Experimental, Facultad de Medicina, Universidad Nacional Autónoma de México Mexico City, Mexico
| | | | - Javier Torres
- Unidad de Investigación Médica en Enfermedades Infecciosas y Parasitarias, Hospital de Pediatría, Centro Médico Nacional Siglo XXI, Instituto Mexicano del Seguro Social, Hospital de Pediatría Mexico City, Mexico
| | - Jorge A González-y-Merchand
- Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional Mexico City, Mexico
| | - María D Alcántar-Curiel
- Unidad de Investigación en Medicina Experimental, Facultad de Medicina, Universidad Nacional Autónoma de México Mexico City, Mexico
| | - Miguel A De la Cruz
- Unidad de Investigación Médica en Enfermedades Infecciosas y Parasitarias, Hospital de Pediatría, Centro Médico Nacional Siglo XXI, Instituto Mexicano del Seguro Social, Hospital de Pediatría Mexico City, Mexico
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Ishihama A, Shimada T, Yamazaki Y. Transcription profile of Escherichia coli: genomic SELEX search for regulatory targets of transcription factors. Nucleic Acids Res 2016; 44:2058-74. [PMID: 26843427 PMCID: PMC4797297 DOI: 10.1093/nar/gkw051] [Citation(s) in RCA: 95] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Accepted: 01/20/2016] [Indexed: 01/25/2023] Open
Abstract
Bacterial genomes are transcribed by DNA-dependent RNA polymerase (RNAP), which achieves gene selectivity through interaction with sigma factors that recognize promoters, and transcription factors (TFs) that control the activity and specificity of RNAP holoenzyme. To understand the molecular mechanisms of transcriptional regulation, the identification of regulatory targets is needed for all these factors. We then performed genomic SELEX screenings of targets under the control of each sigma factor and each TF. Here we describe the assembly of 156 SELEX patterns of a total of 116 TFs performed in the presence and absence of effector ligands. The results reveal several novel concepts: (i) each TF regulates more targets than hitherto recognized; (ii) each promoter is regulated by more TFs than hitherto recognized; and (iii) the binding sites of some TFs are located within operons and even inside open reading frames. The binding sites of a set of global regulators, including cAMP receptor protein, LeuO and Lrp, overlap with those of the silencer H-NS, suggesting that certain global regulators play an anti-silencing role. To facilitate sharing of these accumulated SELEX datasets with the research community, we compiled a database, ‘Transcription Profile of Escherichia coli’ (www.shigen.nig.ac.jp/ecoli/tec/).
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Affiliation(s)
- Akira Ishihama
- Micro-Nano Technology Research Center, Hosei University, Koganei, Tokyo, 184-8584, Japan
| | - Tomohiro Shimada
- Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuda, Yokohama 226-8503, Japan
| | - Yukiko Yamazaki
- National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
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Abstract
Escherichia colicauses three types of illnesses in humans: diarrhea, urinary tract infections, and meningitis in newborns. The acquisition of virulence-associated genes and the ability to properly regulate these, often horizontally transferred, loci distinguishes pathogens from the normally harmless commensal E. coli found within the human intestine. This review addresses our current understanding of virulence gene regulation in several important diarrhea-causing pathotypes, including enteropathogenic, enterohemorrhagic,enterotoxigenic, and enteroaggregativeE. coli-EPEC, EHEC, ETEC and EAEC, respectively. The intensely studied regulatory circuitry controlling virulence of uropathogenicE. coli, or UPEC, is also reviewed, as is that of MNEC, a common cause of meningitis in neonates. Specific topics covered include the regulation of initial attachment events necessary for infection, environmental cues affecting virulence gene expression, control of attaching and effacing lesionformation, and control of effector molecule expression and secretion via the type III secretion systems by EPEC and EHEC. How phage control virulence and the expression of the Stx toxins of EHEC, phase variation, quorum sensing, and posttranscriptional regulation of virulence determinants are also addressed. A number of important virulence regulators are described, including the AraC-like molecules PerA of EPEC, CfaR and Rns of ETEC, and AggR of EAEC;the Ler protein of EPEC and EHEC;RfaH of UPEC;and the H-NS molecule that acts to silence gene expression. The regulatory circuitry controlling virulence of these greatly varied E. colipathotypes is complex, but common themes offerinsight into the signals and regulators necessary forE. coli disease progression.
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Abstract
This review provides a brief review of the current understanding of the structure-function relationship of the Escherichia coli nucleoid developed after the overview by Pettijohn focusing on the physical properties of nucleoids. Isolation of nucleoids requires suppression of DNA expansion by various procedures. The ability to control the expansion of nucleoids in vitro has led to purification of nucleoids for chemical and physical analyses and for high-resolution imaging. Isolated E. coli genomes display a number of individually intertwined supercoiled loops emanating from a central core. Metabolic processes of the DNA double helix lead to three types of topological constraints that all cells must resolve to survive: linking number, catenates, and knots. The major species of nucleoid core protein share functional properties with eukaryotic histones forming chromatin; even the structures are different from histones. Eukaryotic histones play dynamic roles in the remodeling of eukaryotic chromatin, thereby controlling the access of RNA polymerase and transcription factors to promoters. The E. coli genome is tightly packed into the nucleoid, but, at each cell division, the genome must be faithfully replicated, divided, and segregated. Nucleoid activities such as transcription, replication, recombination, and repair are all affected by the structural properties and the special conformations of nucleoid. While it is apparent that much has been learned about the nucleoid, it is also evident that the fundamental interactions organizing the structure of DNA in the nucleoid still need to be clearly defined.
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Abstract
Pathogenic bacteria sense environmental cues, including the local temperature, to control the production of key virulence factors. Thermal regulation can be achieved at the level of DNA, RNA or protein and although many virulence factors are subject to thermal regulation, the exact mechanisms of control are yet to be elucidated in many instances. Understanding how virulence factors are regulated by temperature presents a significant challenge, as gene expression and protein production are often influenced by complex regulatory networks involving multiple transcription factors in bacteria. Here we highlight some recent insights into thermal regulation of virulence in pathogenic bacteria. We focus on bacteria which cause disease in mammalian hosts, which are at a significantly higher temperature than the outside environment. We outline the mechanisms of thermal regulation and how understanding this fundamental aspect of the biology of bacteria has implications for pathogenesis and human health.
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Affiliation(s)
- Oliver Lam
- a The Sir William Dunn School of Pathology ; University of Oxford ; Oxford , UK
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43
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Solórzano C, Srikumar S, Canals R, Juárez A, Paytubi S, Madrid C. Hha has a defined regulatory role that is not dependent upon H-NS or StpA. Front Microbiol 2015; 6:773. [PMID: 26284052 PMCID: PMC4519777 DOI: 10.3389/fmicb.2015.00773] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 07/14/2015] [Indexed: 11/13/2022] Open
Abstract
The Hha family of proteins is involved in the regulation of gene expression in enterobacteria by forming complexes with H-NS-like proteins. Whereas several amino acid residues of both proteins participate in the interaction, some of them play a key role. Residue D48 of Hha protein is essential for the interaction with H-NS, thus the D48N substitution in Hha protein abrogates H-NS/Hha interaction. Despite being a paralog of H-NS protein, StpA interacts with HhaD48N with higher affinity than with the wild type Hha protein. To analyze whether Hha is capable of acting independently of H-NS and StpA, we conducted transcriptomic analysis on the hha and stpA deletion strains and the hhaD48N substitution strain of Salmonella Typhimurium using a custom microarray. The results obtained allowed the identification of 120 genes regulated by Hha in an H-NS/StpA-independent manner, 38% of which are horizontally acquired genes. A significant number of the identified genes are involved in functions related to cell motility, iron uptake, and pathogenicity. Thus, motility assays, siderophore detection and intra-macrophage replication assays were performed to confirm the transcriptomic data. Our findings point out the importance of Hha protein as an independent regulator in S. Typhimurium, highlighting a regulatory role on virulence.
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Affiliation(s)
- Carla Solórzano
- Departament de Microbiologia, Universitat de Barcelona Barcelona, Spain
| | | | - Rocío Canals
- Institute of Integrative Biology, University of Liverpool Liverpool, UK
| | - Antonio Juárez
- Departament de Microbiologia, Universitat de Barcelona Barcelona, Spain ; Institut de Bioenginyeria de Catalunya, Parc Científic de Barcelona Barcelona, Spain
| | - Sonia Paytubi
- Departament de Microbiologia, Universitat de Barcelona Barcelona, Spain
| | - Cristina Madrid
- Departament de Microbiologia, Universitat de Barcelona Barcelona, Spain
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Function of the Histone-Like Protein H-NS in Motility of Escherichia coli: Multiple Regulatory Roles Rather than Direct Action at the Flagellar Motor. J Bacteriol 2015. [PMID: 26195595 DOI: 10.1128/jb.00309-15] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED A number of investigations of Escherichia coli have suggested that the DNA-binding protein H-NS, in addition to its well-known functions in chromosome organization and gene regulation, interacts directly with the flagellar motor to modulate its function. Here, in a study initially aimed at characterizing the H-NS/motor interaction further, we identify problems and limitations in the previous work that substantially weaken the case for a direct H-NS/motor interaction. Null hns mutants are immotile, largely owing to the downregulation of the flagellar master regulators FlhD and FlhC. We, and others, previously reported that an hns mutant remains poorly motile even when FlhDC are expressed constitutively. In the present work, we use better-engineered strains to show that the motility defect in a Δhns, FlhDC-constitutive strain is milder than that reported previously and does not point to a direct action of H-NS at the motor. H-NS regulates numerous genes and might influence motility via a number of regulatory molecules besides FlhDC. To examine the sources of the motility defect that persists in an FlhDC-constitutive Δhns mutant, we measured transcript levels and overexpression effects of a number of genes in candidate regulatory pathways. The results indicate that H-NS influences motility via multiple regulatory linkages that include, minimally, the messenger molecule cyclic di-GMP, the biofilm regulatory protein CsgD, and the sigma factors σ(S) and σ(F). The results are in accordance with the more standard view of H-NS as a regulator of gene expression rather than a direct modulator of flagellar motor performance. IMPORTANCE Data from a number of previous studies have been taken to indicate that the nucleoid-organizing protein H-NS influences motility not only by its well-known DNA-based mechanisms but also by binding directly to the flagellar motor to alter function. In this study, H-NS is shown to influence motility through diverse regulatory pathways, but a direct interaction with the motor is not supported. Previous indications of a direct action at the motor appear to be related to the use of nonnull strains and, in some cases, a failure to effectively bypass the requirement for H-NS in the expression of the flagellar regulon. These findings call for a substantially revised interpretation of the literature concerning H-NS and flagellar motility and highlight the importance of H-NS in diverse regulatory processes involved in the motile-sessile transition.
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Shintani M, Suzuki-Minakuchi C, Nojiri H. Nucleoid-associated proteins encoded on plasmids: Occurrence and mode of function. Plasmid 2015; 80:32-44. [PMID: 25952329 DOI: 10.1016/j.plasmid.2015.04.008] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2015] [Revised: 04/14/2015] [Accepted: 04/22/2015] [Indexed: 01/31/2023]
Abstract
Nucleoid-associated proteins (NAPs) play a role in changing the shape of microbial DNA, making it more compact and affecting the regulation of transcriptional networks in host cells. Genes that encode NAPs include H-NS family proteins (H-NS, Ler, MvaT, BpH3, Bv3F, HvrA, and Lsr2), FIS, HU, IHF, Lrp, and NdpA, and are found in both microbial chromosomes and plasmid DNA. In the present study, NAP genes were distributed among 442 plasmids out of 4602 plasmid sequences, and many H-NS family proteins, and HU, IHF, Lrp, and NdpA were found in plasmids of Alpha-, Beta-, and Gammaproteobacteria, while HvrA, Lsr2, HU, and Lrp were found in other classes including Actinobacteria and Bacilli. Larger plasmids frequently carried multiple NAP genes. In addition, NAP genes were more frequently found in conjugative plasmids than non-transmissible plasmids. Several host cells carried the same types of H-NS family proteins on both their plasmids and chromosome(s), while this was not observed for other NAPs. Recent studies have shown that NAP genes on plasmids and chromosomes play important roles in the physical and regulatory integration of plasmids into the host cell.
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Affiliation(s)
- Masaki Shintani
- Applied Chemistry and Biochemical Engineering Course, Department of Engineering, Graduate School of Integrated Science and Technology, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu, Shizuoka 432-8561, Japan; Department of Bioscience, Graduate School of Science and Technology, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu, Shizuoka 432-8561, Japan
| | - Chiho Suzuki-Minakuchi
- Biotechnology Research Center, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Hideaki Nojiri
- Biotechnology Research Center, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
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Effects of three different nucleoid-associated proteins encoded on IncP-7 plasmid pCAR1 on host Pseudomonas putida KT2440. Appl Environ Microbiol 2015; 81:2869-80. [PMID: 25681185 DOI: 10.1128/aem.00023-15] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Nucleoid-associated proteins (NAPs), which fold bacterial DNA and influence gene transcription, are considered to be global transcriptional regulators of genes on both plasmids and the host chromosome. Incompatibility P-7 group plasmid pCAR1 carries genes encoding three NAPs: H-NS family protein Pmr, NdpA-like protein Pnd, and HU-like protein Phu. In this study, the effects of single or double disruption of pmr, pnd, and phu were assessed in host Pseudomonas putida KT2440. When pmr and pnd or pmr and phu were simultaneously disrupted, both the segregational stability and the structural stability of pCAR1 were markedly decreased, suggesting that Pmr, Pnd, and Phu act as plasmid-stabilizing factors in addition to their established roles in replication and partition systems. The transfer frequency of pCAR1 was significantly decreased in these double mutants. The segregational and structural instability of pCAR1 in the double mutants was recovered by complementation of pmr, whereas no recovery of transfer deficiency was observed. Comprehensive phenotype comparisons showed that the host metabolism of carbon compounds, which was reduced by pCAR1 carriage, was restored by disruption of the NAP gene(s). Transcriptome analyses of mutants indicated that transcription of genes for energy production, conversion, inorganic ion transport, and metabolism were commonly affected; however, how their products altered the phenotypes of mutants was not clear. The findings of this study indicated that Pmr, Pnd, and Phu act synergistically to affect pCAR1 replication, maintenance, and transfer, as well as to alter the host metabolic phenotype.
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Winardhi RS, Castang S, Dove SL, Yan J. Single-molecule study on histone-like nucleoid-structuring protein (H-NS) paralogue in Pseudomonas aeruginosa: MvaU bears DNA organization mode similarities to MvaT. PLoS One 2014; 9:e112246. [PMID: 25372370 PMCID: PMC4221281 DOI: 10.1371/journal.pone.0112246] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Accepted: 10/13/2014] [Indexed: 11/18/2022] Open
Abstract
Pseudomonas aeruginosa contains two distinct members of H-NS family of nucleoid-structuring proteins: MvaT and MvaU. Together, these proteins bind to the same regions of the chromosome and function coordinately in the regulation of hundreds of genes. Due to their structural similarity, they can associate to form heteromeric complexes. These findings left us wondering whether they bear similar DNA binding properties that underlie their gene-silencing functions. Using single-molecule stretching and imaging experiments, we found striking similarities in the DNA organization modes of MvaU compared to the previously studied MvaT. MvaU can form protective nucleoprotein filaments that are insensitive to environmental factors, consistent with its role as a repressor of gene expression. Similar to MvaT, MvaU filament can mediate DNA bridging while excessive MvaU can cause DNA aggregation. The almost identical DNA organization modes of MvaU and MvaT explain their functional redundancy, and raise an interesting question regarding the evolutionary benefits of having multiple H-NS paralogues in the Pseudomonas genus.
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Affiliation(s)
- Ricksen S. Winardhi
- NUS Graduate school for Integrative Sciences and Engineering, Singapore, Singapore
- Mechanobiology Institute, National University of Singapore, Singapore, Singapore
- Centre for Bioimaging Sciences, National University of Singapore, Singapore, Singapore
| | - Sandra Castang
- Division of Infectious Diseases, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Simon L. Dove
- Division of Infectious Diseases, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Jie Yan
- Mechanobiology Institute, National University of Singapore, Singapore, Singapore
- Centre for Bioimaging Sciences, National University of Singapore, Singapore, Singapore
- Department of Physics, National University of Singapore, Singapore, Singapore
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Zhang J, Xiao J, Zhang Y, Cui S, Liu Q, Wang Q, Wu H, Zhang Y. A new target for the old regulator: H-NS suppress T6SS secretory protein EvpP, the major virulence factor in the fish pathogen Edwardsiella tarda. Lett Appl Microbiol 2014; 59:557-64. [PMID: 25131176 DOI: 10.1111/lam.12316] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Revised: 07/28/2014] [Accepted: 08/06/2014] [Indexed: 11/29/2022]
Abstract
UNLABELLED The evpP gene in fish pathogen Edwardsiella tarda, coding the T6SS secretory protein EvpP and carrying an evpA-evpO independent promoter region, was crucial for host cell invasion. The transcription of evpP was positively regulated by either the two-component system EsrA-EsrB or iron concentration, and its overexpression was known to enhance the invasion ability in our previous study. This work demonstrated that the H-NS protein, a pleiotropic regulator of gene expression, was a new transcriptional modulator of evpP gene. The results showed that in vivo the transcriptional level of evpP was downregulated by H-NS and in vitro this global regulator interacted directly with evpP promoter region. Moreover, DNase I footprinting experiments mapping the interaction regions of H-NS and evpP revealed that this global regulator bound to evpP promoter and neighbouring areas at multiple sites. We provided a new insight into evpP regulation network and demonstrated the repression of H-NS to the transcription of evpP gene. SIGNIFICANCE AND IMPACT OF THE STUDY Recently, the devastating fish disease edwardsiellosis caused by Edwardsiella tarda has been widely concerned. The xenogeneic silencing of the classic regulator H-NS to the T6SS secretory protein EvpP, which played an important role in the virulence of Edw. tarda, was firstly reported in this study. It raised a better understanding of the virulence regulation of EvpP and provided more information about the complex infection mechanism of this pathogen. Our findings would contribute to the development of live attenuated vaccines against edwardsiellosis thus reducing the economic losses caused by this bacterium.
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Affiliation(s)
- J Zhang
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, China
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Suzuki C, Kawazuma K, Horita S, Terada T, Tanokura M, Okada K, Yamane H, Nojiri H. Oligomerization mechanisms of an H-NS family protein, Pmr, encoded on the plasmid pCAR1 provide a molecular basis for functions of H-NS family members. PLoS One 2014; 9:e105656. [PMID: 25137042 PMCID: PMC4138198 DOI: 10.1371/journal.pone.0105656] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Accepted: 07/26/2014] [Indexed: 11/19/2022] Open
Abstract
Enterobacterial H-NS-like proteins and Pseudomonas MvaT-like proteins share low homology at the amino acid sequence level, but both can function as xenogeneic silencers and are included in the H-NS family of proteins. H-NS family members have dimerization/oligomerization and DNA-binding domains connected by a flexible linker and form large nucleoprotein complexes using both domains. Pmr, an MvaT-like protein encoded on the IncP-7 carbazole-degradative plasmid pCAR1, is a key regulator of an interaction between pCAR1 and its host Pseudomonas putida KT2440. KT2440 has two transcribed genes that encode the MvaT-like proteins TurA and TurB. Our previous transcriptome analyses suggested that the functions of Pmr, TurA and TurB are non-equivalent, although the detailed underlying mechanisms remain unclear. In this study, we focused on the protein–protein interactions of Pmr, and assessed the homo-oligomerization capacity of various substituted and truncated Pmr derivatives by protein–protein cross-linking analysis. Six of the seven residues identified as important for homo-oligomerization in Pmr were located near the N-terminus, and the putative flexible linker or the region near that was not involved in homo-oligomerization, suggesting that Pmr homo-oligomerization is different from that of enterobacterial H-NS and that the functional mechanism differs between H-NS-like and MvaT-like proteins. In addition, we assessed homo- and hetero-oligomerization of Pmr by surface plasmon resonance analysis and found that the coupling ratio of TurB-Pmr oligomers is smaller than that of Pmr-Pmr or TurA-Pmr oligomers. These results raised the possibility that composition of the hetero-oligomers of Pmr, TurA, and TurB could explain why the different gene sets were affected by either pmr, turA, or turB disruption in our previous studies.
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Affiliation(s)
- Chiho Suzuki
- Biotechnology Research Center, The University of Tokyo, Tokyo, Japan
| | - Kohei Kawazuma
- Biotechnology Research Center, The University of Tokyo, Tokyo, Japan
| | - Shoichiro Horita
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Tohru Terada
- Agricultural Bioinformatics Research Unit, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Masaru Tanokura
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Kazunori Okada
- Biotechnology Research Center, The University of Tokyo, Tokyo, Japan
| | - Hisakazu Yamane
- Biotechnology Research Center, The University of Tokyo, Tokyo, Japan
| | - Hideaki Nojiri
- Biotechnology Research Center, The University of Tokyo, Tokyo, Japan
- Agricultural Bioinformatics Research Unit, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
- * E-mail:
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H-NS is a novel transcriptional modulator of the ribonucleotide reductase genes in Escherichia coli. J Bacteriol 2013; 195:4255-63. [PMID: 23873909 DOI: 10.1128/jb.00490-13] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Ribonucleotide reductases (RNRs) are essential enzymes for DNA synthesis because they are responsible for the production of the four deoxyribonucleotides (dNTPs) from their corresponding ribonucleotides. Escherichia coli contains two classes of aerobic RNRs, encoded by the nrdAB (class Ia) and nrdHIEF (class Ib) operons, and a third RNR class, which is functional under anaerobic conditions and is encoded by the nrdDG (class III) operon. Because cellular imbalances in the amounts of the four dNTPs cause an increase in the rate of mutagenesis, the activity and the expression of RNRs must be tightly regulated during bacterial chromosome replication. The transcriptional regulation of these genes requires several transcription factors (including DnaA, IciA, FIS [factor for inversion stimulation], Fnr, Fur, and NrdR), depending on the RNR class; however, the factors that dictate the expression of some RNR genes in response to different environmental conditions are not known. We show that H-NS modulates the expression of the nrdAB and nrdDG operons. H-NS represses expression both in aerobically and in anaerobically growing cells. Under aerobic conditions, repression occurs at the exponential phase of growth as well as at the transition from the exponential to the stationary phase, a period when no dNTPs are needed. Under anoxic conditions, repression occurs mainly in exponentially growing cells. Electrophoretic mobility assays performed with two DNA fragments from the regulatory region of the nrdAB operon demonstrated the direct interaction of H-NS with these sequences.
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