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Cortés-Avalos D, Borges Farias A, Romero-González LE, Lara-Ochoa C, Villa-Tanaca L, García-Del Portillo F, López-Guerrero V, Bustamante VH, Pérez-Rueda E, Ibarra JA. Interactions between the AraC/XylS-like transcriptional activator InvF of Salmonella Typhimurium, the RNA polymerase alpha subunit and the chaperone SicA. Sci Rep 2024; 14:156. [PMID: 38167847 PMCID: PMC10761746 DOI: 10.1038/s41598-023-50636-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: 11/07/2023] [Accepted: 12/22/2023] [Indexed: 01/05/2024] Open
Abstract
Salmonella enterica serovar Typhimurium causes gastroenteritis and systemic infections in humans. For this bacterium the expression of a type III secretion system (T3SS) and effector proteins encoded in the Salmonella pathogenicity island-1 (SPI-1), is keystone for the virulence of this bacterium. Expression of these is controlled by a regulatory cascade starting with the transcriptional regulators HilD, HilC and RtsA that induce the expression of HilA, which then activates expression of the regulator InvF, a transcriptional regulator of the AraC/XylS family. InvF needs to interact with the chaperone SicA to activate transcription of SPI-1 genes including sicA, sopB, sptP, sopE, sopE2, and STM1239. InvF very likely acts as a classical activator; however, whether InvF interacts with the RNA polymerase alpha subunit RpoA has not been determined. Results from this study confirm the interaction between InvF with SicA and reveal that both proteins interact with the RNAP alpha subunit. Thus, our study further supports that the InvF/SicA complex acts as a classical activator. Additionally, we showed for the first time an interaction between a chaperone of T3SS effectors (SicA) and the RNAP.
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Affiliation(s)
- Daniel Cortés-Avalos
- Laboratorio de Genética Microbiana, Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional. Prol. Carpio y Plan de Ayala S/N, Col. Santo Tomás 11340, Mexico City, Mexico
| | - André Borges Farias
- Instituto de Investigaciones en Matemáticas Aplicadas y en Sistemas, Universidad Nacional Autónoma de México, Unidad Académica del Estado de Yucatán, Mérida, Mexico
| | - Luis E Romero-González
- Laboratorio de Genética Microbiana, Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional. Prol. Carpio y Plan de Ayala S/N, Col. Santo Tomás 11340, Mexico City, Mexico
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico
| | - Cristina Lara-Ochoa
- Centro de Detección Biomolecular, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
| | - Lourdes Villa-Tanaca
- Laboratorio de Genética Microbiana, Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional. Prol. Carpio y Plan de Ayala S/N, Col. Santo Tomás 11340, Mexico City, Mexico
| | - Francisco García-Del Portillo
- Laboratory of Intracellular Bacterial Pathogens, National Centre for Biotechnology (CNB)-CSIC, Darwin, 3, 28049, Madrid, Spain
| | - Vanessa López-Guerrero
- Facultad de Medicina, Universidad Autónoma del Estado de Morelos, Cuernavaca, Morelos, Mexico
| | - Víctor H Bustamante
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico
| | - Ernesto Pérez-Rueda
- Instituto de Investigaciones en Matemáticas Aplicadas y en Sistemas, Universidad Nacional Autónoma de México, Unidad Académica del Estado de Yucatán, Mérida, Mexico
| | - J Antonio Ibarra
- Laboratorio de Genética Microbiana, Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional. Prol. Carpio y Plan de Ayala S/N, Col. Santo Tomás 11340, Mexico City, Mexico.
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2
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Lara-Ochoa C, González-Lara F, Romero-González LE, Jaramillo-Rodríguez JB, Vázquez-Arellano SI, Medrano-López A, Cedillo-Ramírez L, Martínez-Laguna Y, Girón JA, Pérez-Rueda E, Puente JL, Ibarra JA. The transcriptional activator of the bfp operon in EPEC (PerA) interacts with the RNA polymerase alpha subunit. Sci Rep 2021; 11:8541. [PMID: 33879812 PMCID: PMC8058060 DOI: 10.1038/s41598-021-87586-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2020] [Accepted: 03/30/2021] [Indexed: 11/09/2022] Open
Abstract
Enteropathogenic E. coli virulence genes are under the control of various regulators, one of which is PerA, an AraC/XylS-like regulator. PerA directly promotes its own expression and that of the bfp operon encoding the genes involved in the biogenesis of the bundle-forming pilus (BFP); it also activates PerC expression, which in turn stimulates locus of enterocyte effacement (LEE) activation through the LEE-encoded regulator Ler. Monomeric PerA directly binds to the per and bfp regulatory regions; however, it is not known whether interactions between PerA and the RNA polymerase (RNAP) are needed to activate gene transcription as has been observed for other AraC-like regulators. Results showed that PerA interacts with the alpha subunit of the RNAP polymerase and that it is necessary for the genetic and phenotypic expression of bfpA. Furthermore, an in silico analysis shows that PerA might be interacting with specific alpha subunit amino acids residues highlighting the direction of future experiments.
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Affiliation(s)
- Cristina Lara-Ochoa
- Centro de Detección Biomolecular, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico.
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico.
| | - Fabiola González-Lara
- Centro de Detección Biomolecular, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico
| | - Luis E Romero-González
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico
- Laboratorio de Genética Microbiana, Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Mexico City, Mexico
| | - Juan B Jaramillo-Rodríguez
- Centro de Detección Biomolecular, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico
| | | | - Abraham Medrano-López
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico
| | - Lilia Cedillo-Ramírez
- Centro de Detección Biomolecular, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
| | - Ygnacio Martínez-Laguna
- Centro de Detección Biomolecular, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
- Vicerrectoría de Investigación y Estudios de Posgrado, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
| | - Jorge A Girón
- Centro de Detección Biomolecular, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
| | - Ernesto Pérez-Rueda
- Instituto de Investigaciones en Matemáticas Aplicadas y en Sistemas, Universidad Nacional Autónoma de México, Unidad Académica Yucatán, Mérida, Mexico
| | - José Luis Puente
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico
| | - J Antonio Ibarra
- Laboratorio de Genética Microbiana, Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Mexico City, Mexico.
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3
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Cortés-Avalos D, Martínez-Pérez N, Ortiz-Moncada MA, Juárez-González A, Baños-Vargas AA, Estrada-de Los Santos P, Pérez-Rueda E, Ibarra JA. An update of the unceasingly growing and diverse AraC/XylS family of transcriptional activators. FEMS Microbiol Rev 2021; 45:6219864. [PMID: 33837749 DOI: 10.1093/femsre/fuab020] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 03/31/2021] [Indexed: 01/09/2023] Open
Abstract
Transcriptional factors play an important role in gene regulation in all organisms, especially in Bacteria. Here special emphasis is placed in the AraC/XylS family of transcriptional regulators. This is one of the most abundant as many predicted members have been identified and more members are added because more bacterial genomes are sequenced. Given the way more experimental evidence has mounded in the past decades, we decided to update the information about this captivating family of proteins. Using bioinformatics tools on all the data available for experimentally characterized members of this family, we found that many members that display a similar functional classification can be clustered together and in some cases they have a similar regulatory scheme. A proposal for grouping these proteins is also discussed. Additionally, an analysis of surveyed proteins in bacterial genomes is presented. Altogether, the current review presents a panoramic view into this family and we hope it helps to stimulate future research in the field.
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Affiliation(s)
- Daniel Cortés-Avalos
- Laboratorio de Genética Microbiana, Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Ciudad de México, México
| | - Noemy Martínez-Pérez
- Instituto de Investigaciones en Matemáticas Aplicadas y en Sistemas, Universidad Nacional Autónoma de México, Unidad Académica Yucatán, Mérida, Yucatán, México
| | - Mario A Ortiz-Moncada
- Laboratorio de Genética Microbiana, Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Ciudad de México, México
| | - Aylin Juárez-González
- Laboratorio de Genética Microbiana, Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Ciudad de México, México
| | - Arturo A Baños-Vargas
- Laboratorio de Genética Microbiana, Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Ciudad de México, México
| | - Paulina Estrada-de Los Santos
- Laboratorio de Biotecnología Microbiana, Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Ciudad de México, México
| | - Ernesto Pérez-Rueda
- Instituto de Investigaciones en Matemáticas Aplicadas y en Sistemas, Universidad Nacional Autónoma de México, Unidad Académica Yucatán, Mérida, Yucatán, México.,Facultad de Ciencias, Centro de Genómica y Bioinformática, Universidad Mayor, Santiago, Chile
| | - J Antonio Ibarra
- Laboratorio de Genética Microbiana, Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Ciudad de México, México
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Backbone Interactions Between Transcriptional Activator ExsA and Anti-Activator ExsD Facilitate Regulation of the Type III Secretion System in Pseudomonas aeruginosa. Sci Rep 2020; 10:9881. [PMID: 32555263 PMCID: PMC7303211 DOI: 10.1038/s41598-020-66555-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Accepted: 05/20/2020] [Indexed: 12/20/2022] Open
Abstract
The type III secretion system (T3SS) is a pivotal virulence mechanism of many Gram-negative bacteria. During infection, the syringe-like T3SS injects cytotoxic proteins directly into the eukaryotic host cell cytoplasm. In Pseudomonas aeruginosa, expression of the T3SS is regulated by a signaling cascade involving the proteins ExsA, ExsC, ExsD, and ExsE. The AraC-type transcription factor ExsA activates transcription of all T3SS-associated genes. Prior to host cell contact, ExsA is inhibited through direct binding of the anti-activator protein ExsD. Host cell contact triggers secretion of ExsE and sequestration of ExsD by ExsC to cause the release of ExsA. ExsA does not bind ExsD through the canonical ligand binding pocket of AraC-type proteins. Using site-directed mutagenesis and a specific in vitro transcription assay, we have now discovered that backbone interactions between the amino terminus of ExsD and the ExsA beta barrel constitute a pivotal part of the ExsD-ExsA interface. Follow-up bacterial two-hybrid experiments suggest additional contacts create an even larger protein–protein interface. The discovered role of the amino terminus of ExsD in ExsA binding explains how ExsC might relieve the ExsD-mediated inhibition of T3SS gene expression, because the same region of ExsD interacts with ExsC following host cell contact.
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King MM, Kayastha BB, Franklin MJ, Patrauchan MA. Calcium Regulation of Bacterial Virulence. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1131:827-855. [PMID: 31646536 DOI: 10.1007/978-3-030-12457-1_33] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Calcium (Ca2+) is a universal signaling ion, whose major informational role shaped the evolution of signaling pathways, enabling cellular communications and responsiveness to both the intracellular and extracellular environments. Elaborate Ca2+ regulatory networks have been well characterized in eukaryotic cells, where Ca2+ regulates a number of essential cellular processes, ranging from cell division, transport and motility, to apoptosis and pathogenesis. However, in bacteria, the knowledge on Ca2+ signaling is still fragmentary. This is complicated by the large variability of environments that bacteria inhabit with diverse levels of Ca2+. Yet another complication arises when bacterial pathogens invade a host and become exposed to different levels of Ca2+ that (1) are tightly regulated by the host, (2) control host defenses including immune responses to bacterial infections, and (3) become impaired during diseases. The invading pathogens evolved to recognize and respond to the host Ca2+, triggering the molecular mechanisms of adhesion, biofilm formation, host cellular damage, and host-defense resistance, processes enabling the development of persistent infections. In this review, we discuss: (1) Ca2+ as a determinant of a host environment for invading bacterial pathogens, (2) the role of Ca2+ in regulating main events of host colonization and bacterial virulence, and (3) the molecular mechanisms of Ca2+ signaling in bacterial pathogens.
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Affiliation(s)
- Michelle M King
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, USA
| | - Biraj B Kayastha
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, USA
| | - Michael J Franklin
- Department of Microbiology and Center for Biofilm Engineering, Montana State University, Bozeman, MT, USA
| | - Marianna A Patrauchan
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, USA.
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Soni N, Swain SK, Kant R, Singh A, Ravichandran R, Verma SK, Panda PK, Suar M. Landscape of ROD9 Island: Functional annotations and biological network of hypothetical proteins in Salmonella enterica. Comput Biol Chem 2019; 83:107110. [PMID: 31445418 DOI: 10.1016/j.compbiolchem.2019.107110] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2018] [Revised: 07/16/2019] [Accepted: 08/13/2019] [Indexed: 01/01/2023]
Abstract
Salmonella, an Enterobacteria is a therapeutically important pathogen for the host. The advancement of genome sequencing of S. enterica serovar Enteritidis have identified a distinct ROD9 pathogenic island, imparting virulence. The occurrence of 17 ROD9 hypothetical proteins, necessitates subsequent bioinformatics approach for structural and functional aspects of protein-protein relations or networks in different pathogenic phenotypes express. A collective analysis using predictive bioinformatics tools that includes NCBI-BLASTp and BLAST2GO annotated the motif patterns and functional significance. The VFDB identified 10 virulence proteins at both genomic and metagenomic level. Phylogenetic analysis revealed a divergent and convergent relationship between 17 ROD9 and 41 SP-1 proteins. Here, combining a comprehensive approach from sequence based, motif recognitions, domain identification, virulence ability to structural modelling provides a precise function to ROD9 proteins biological network, for which no experimental information is available.
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Affiliation(s)
- Nikita Soni
- School of Biotechnology and Bioinformatics, D. Y. Patil (Deemed to be University), Navi Mumbai, India
| | | | - Ravi Kant
- University of Delhi, New Delhi, India
| | - Aditya Singh
- School of Biotechnology and Bioinformatics, D. Y. Patil (Deemed to be University), Navi Mumbai, India
| | - Rahul Ravichandran
- School of Chemical and Biotechnology, SASTRA University, Tamil Nadu, India
| | - Suresh K Verma
- Institute of Environmental Medicine (IMM), C6, Molecular Toxicology, Karolinska Institutet, Sweden
| | - Pritam Kumar Panda
- Division of Pediatric Hematology and Oncology, University Medical Center, University of Freiburg, Germany.
| | - Mrutyunjay Suar
- School of Biotechnology, KIIT University, Bhubaneswar, India.
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Pseudomonas aeruginosa Magnesium Transporter MgtE Inhibits Type III Secretion System Gene Expression by Stimulating rsmYZ Transcription. J Bacteriol 2017; 199:JB.00268-17. [PMID: 28847924 DOI: 10.1128/jb.00268-17] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Accepted: 08/23/2017] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas aeruginosa causes numerous acute and chronic opportunistic infections in humans. One of its most formidable weapons is a type III secretion system (T3SS), which injects powerful toxins directly into host cells. The toxins lead to cell dysfunction and, ultimately, cell death. Identification of regulatory pathways that control T3SS gene expression may lead to the discovery of novel therapeutics to treat P. aeruginosa infections. In a previous study, we found that expression of the magnesium transporter gene mgtE inhibits T3SS gene transcription. MgtE-dependent inhibition appeared to interfere with the synthesis or function of the master T3SS transcriptional activator ExsA, although the exact mechanism was unclear. We now demonstrate that mgtE expression acts through the GacAS two-component system to activate rsmY and rsmZ transcription. This event ultimately leads to inhibition of exsA translation. This inhibitory effect is specific to exsA as translation of other genes in the exsCEBA operon is not inhibited by mgtE Moreover, our data reveal that MgtE acts solely through this pathway to regulate T3SS gene transcription. Our study reveals an important mechanism that may allow P. aeruginosa to fine-tune T3SS activity in response to certain environmental stimuli.IMPORTANCE The type III secretion system (T3SS) is a critical virulence factor utilized by numerous Gram-negative bacteria, including Pseudomonas aeruginosa, to intoxicate and kill host cells. Elucidating T3SS regulatory mechanisms may uncover targets for novel anti-P. aeruginosa therapeutics and provide deeper understanding of bacterial pathogenesis. We previously found that the magnesium transporter MgtE inhibits T3SS gene transcription in P. aeruginosa In this study, we describe the mechanism of MgtE-dependent inhibition of the T3SS. Our report also illustrates how MgtE might respond to environmental cues, such as magnesium levels, to fine-tune T3SS gene expression.
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Vakulskas CA, Leng Y, Abe H, Amaki T, Okayama A, Babitzke P, Suzuki K, Romeo T. Antagonistic control of the turnover pathway for the global regulatory sRNA CsrB by the CsrA and CsrD proteins. Nucleic Acids Res 2016; 44:7896-910. [PMID: 27235416 PMCID: PMC5027483 DOI: 10.1093/nar/gkw484] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 05/18/2016] [Indexed: 12/20/2022] Open
Abstract
The widely conserved protein CsrA (carbon storage regulator A) globally regulates bacterial gene expression at the post-transcriptional level. In many species, CsrA activity is governed by untranslated sRNAs, CsrB and CsrC in Escherichia coli, which bind to multiple CsrA dimers, sequestering them from lower affinity mRNA targets. Both the synthesis and turnover of CsrB/C are regulated. Their turnover requires the housekeeping endonuclease RNase E and is activated by the presence of a preferred carbon source via the binding of EIIAGlc of the glucose transport system to the GGDEF-EAL domain protein CsrD. We demonstrate that the CsrB 3′ segment contains the features necessary for CsrD-mediated decay. RNase E cleavage in an unstructured segment located immediately upstream from the intrinsic terminator is necessary for subsequent degradation to occur. CsrA stabilizes CsrB against RNase E cleavage by binding to two canonical sites adjacent to the necessary cleavage site, while CsrD acts by overcoming CsrA-mediated protection. Our genetic, biochemical and structural studies establish a molecular framework for sRNA turnover by the CsrD-RNase E pathway. We propose that CsrD evolution was driven by the selective advantage of decoupling Csr sRNA decay from CsrA binding, connecting it instead to the availability of a preferred carbon source.
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Affiliation(s)
- Christopher A Vakulskas
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611-0700, USA
| | - Yuanyuan Leng
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611-0700, USA
| | - Hazuki Abe
- Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan
| | - Takumi Amaki
- Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan
| | - Akihiro Okayama
- Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan
| | - Paul Babitzke
- Department of Applied Biological Chemistry, Faculty of Agriculture, Niigata University, Niigata 950-2181, Japan
| | - Kazushi Suzuki
- Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan Department of Biochemistry and Molecular Biology, Center for RNA Molecular Biology, Pennsylvania State University, University Park, PA 16802, USA
| | - Tony Romeo
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611-0700, USA
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Shen L, Macnaughtan MA, Frohlich KM, Cong Y, Goodwin OY, Chou CW, LeCour L, Krup K, Luo M, Worthylake DK. Multipart Chaperone-Effector Recognition in the Type III Secretion System of Chlamydia trachomatis. J Biol Chem 2015; 290:28141-28155. [PMID: 26438824 DOI: 10.1074/jbc.m115.670232] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Indexed: 11/06/2022] Open
Abstract
Secretion of effector proteins into the eukaryotic host cell is required for Chlamydia trachomatis virulence. In the infection process, Scc1 and Scc4, two chaperones of the type III secretion (T3S) system, facilitate secretion of the important effector and plug protein, CopN, but little is known about the details of this event. Here we use biochemistry, mass spectrometry, nuclear magnetic resonance spectroscopy, and genetic analyses to characterize this trimolecular event. We find that Scc4 complexes with Scc1 and CopN in situ at the late developmental cycle of C. trachomatis. We show that Scc4 and Scc1 undergo dynamic interactions as part of the unique bacterial developmental cycle. Using alanine substitutions, we identify several amino acid residues in Scc4 that are critical for the Scc4-Scc1 interaction, which is required for forming the Scc4·Scc1·CopN ternary complex. These results, combined with our previous findings that Scc4 plays a role in transcription (Rao, X., Deighan, P., Hua, Z., Hu, X., Wang, J., Luo, M., Wang, J., Liang, Y., Zhong, G., Hochschild, A., and Shen, L. (2009) Genes Dev. 23, 1818-1829), reveal that the T3S process is linked to bacterial transcriptional events, all of which are mediated by Scc4 and its interacting proteins. A model describing how the T3S process may affect gene expression is proposed.
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Affiliation(s)
- Li Shen
- Department of Microbiology, Immunology, and Parasitology.
| | - Megan A Macnaughtan
- Department of Chemistry, Louisiana State University, Baton Range, Louisiana 70803
| | | | - Yanguang Cong
- Department of Microbiology, Immunology, and Parasitology
| | - Octavia Y Goodwin
- Department of Chemistry, Louisiana State University, Baton Range, Louisiana 70803
| | - Chau-Wen Chou
- Department of Chemistry, University of Georgia, Athens, Georgia 30602
| | - Louis LeCour
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112
| | - Kristen Krup
- Department of Microbiology, Immunology, and Parasitology
| | - Miao Luo
- Department of Microbiology, Immunology, and Parasitology
| | - David K Worthylake
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112
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10
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Shrestha M, Xiao Y, Robinson H, Schubot FD. Structural Analysis of the Regulatory Domain of ExsA, a Key Transcriptional Regulator of the Type Three Secretion System in Pseudomonas aeruginosa. PLoS One 2015; 10:e0136533. [PMID: 26317977 PMCID: PMC4552939 DOI: 10.1371/journal.pone.0136533] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 08/04/2015] [Indexed: 12/30/2022] Open
Abstract
Pseudomonas aeruginosa employs a type three secretion system to facilitate infections in mammalian hosts. The operons encoding genes of structural components of the secretion machinery and associated virulence factors are all under the control of the AraC-type transcriptional activator protein, ExsA. ExsA belongs to a unique subfamily of AraC-proteins that is regulated through protein-protein contacts rather than small molecule ligands. Prior to infection, ExsA is inhibited through a direct interaction with the anti-activator ExsD. To activate ExsA upon host cell contact this interaction is disrupted by the anti-antiactivator protein ExsC. Here we report the crystal structure of the regulatory domain of ExsA, which is known to mediate ExsA dimerization as well as ExsD binding. The crystal structure suggests two models for the ExsA dimer. Both models confirmed the previously shown involvement of helix α-3 in ExsA dimerization but one also suggest a role for helix α-2. These structural data are supported by the observation that a mutation in α-2 greatly diminished the ability of ExsA to activate transcription in vitro. Additional in vitro transcription studies revealed that a conserved pocket, used by AraC and the related ToxT protein for the binding of small molecule regulators, although present in ExsA is not involved in binding of ExsD.
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Affiliation(s)
- Manisha Shrestha
- Department of Biological Sciences, Virginia Polytechnic Institute & State University, Washington Street, Blacksburg, VA 24060, United States of America
| | - Yi Xiao
- Department of Biological Sciences, Virginia Polytechnic Institute & State University, Washington Street, Blacksburg, VA 24060, United States of America
| | - Howard Robinson
- Biology Department, Brookhaven National Laboratory, Upton, NY 11973–5000, United States of America
| | - Florian D. Schubot
- Department of Biological Sciences, Virginia Polytechnic Institute & State University, Washington Street, Blacksburg, VA 24060, United States of America
- * E-mail:
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11
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Vakulskas CA, Potts AH, Babitzke P, Ahmer BMM, Romeo T. Regulation of bacterial virulence by Csr (Rsm) systems. Microbiol Mol Biol Rev 2015; 79:193-224. [PMID: 25833324 PMCID: PMC4394879 DOI: 10.1128/mmbr.00052-14] [Citation(s) in RCA: 243] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Most bacterial pathogens have the remarkable ability to flourish in the external environment and in specialized host niches. This ability requires their metabolism, physiology, and virulence factors to be responsive to changes in their surroundings. It is no surprise that the underlying genetic circuitry that supports this adaptability is multilayered and exceedingly complex. Studies over the past 2 decades have established that the CsrA/RsmA proteins, global regulators of posttranscriptional gene expression, play important roles in the expression of virulence factors of numerous proteobacterial pathogens. To accomplish these tasks, CsrA binds to the 5' untranslated and/or early coding regions of mRNAs and alters translation, mRNA turnover, and/or transcript elongation. CsrA activity is regulated by noncoding small RNAs (sRNAs) that contain multiple CsrA binding sites, which permit them to sequester multiple CsrA homodimers away from mRNA targets. Environmental cues sensed by two-component signal transduction systems and other regulatory factors govern the expression of the CsrA-binding sRNAs and, ultimately, the effects of CsrA on secretion systems, surface molecules and biofilm formation, quorum sensing, motility, pigmentation, siderophore production, and phagocytic avoidance. This review presents the workings of the Csr system, the paradigm shift that it generated for understanding posttranscriptional regulation, and its roles in virulence networks of animal and plant pathogens.
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Affiliation(s)
- Christopher A Vakulskas
- Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida, USA
| | - Anastasia H Potts
- Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida, USA
| | - Paul Babitzke
- Department of Biochemistry and Molecular Biology, Center for RNA Molecular Biology, Pennsylvania State University, University Park, Pennsylvania, USA
| | - Brian M M Ahmer
- Department of Microbial Infection and Immunity, The Ohio State University, Columbus, Ohio, USA Department of Microbiology, The Ohio State University, Columbus, Ohio, USA
| | - Tony Romeo
- Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida, USA
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ExsA and LcrF recognize similar consensus binding sites, but differences in their oligomeric state influence interactions with promoter DNA. J Bacteriol 2013; 195:5639-50. [PMID: 24142246 DOI: 10.1128/jb.00990-13] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
ExsA activates type III secretion system (T3SS) gene expression in Pseudomonas aeruginosa and is a member of the AraC family of transcriptional regulators. AraC proteins contain two helix-turn-helix (HTH) DNA binding motifs. One helix from each HTH motif inserts into the major groove of the DNA to make base-specific contacts with the promoter region. The amino acids that comprise the HTH motifs of ExsA are nearly identical to those in LcrF/VirF, the activators of T3SS gene expression in the pathogenic yersiniae. In this study, we tested the hypothesis that ExsA/LcrF/VirF recognize a common nucleotide sequence. We report that Yersinia pestis LcrF binds to and activates transcription of ExsA-dependent promoters in P. aeruginosa and that plasmid-expressed ExsA complements a Y. pestis lcrF mutant for T3SS gene expression. Mutations that disrupt the ExsA consensus binding sites in both P. aeruginosa and Y. pestis T3SS promoters prevent activation by ExsA and LcrF. Our combined data demonstrate that ExsA and LcrF recognize a common nucleotide sequence. Nevertheless, the DNA binding properties of ExsA and LcrF are distinct. Whereas two ExsA monomers are sequentially recruited to the promoter region, LcrF binds to promoter DNA as a preformed dimer and has a higher capacity to bend DNA. An LcrF mutant defective for dimerization bound promoter DNA with properties similar to ExsA. Finally, we demonstrate that the activators of T3SS gene expression from Photorhabdus luminescens, Aeromonas hydrophila, and Vibrio parahaemolyticus are also sensitive to mutations that disrupt the ExsA consensus binding site.
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Diaz MR, King JM, Yahr TL. Intrinsic and Extrinsic Regulation of Type III Secretion Gene Expression in Pseudomonas Aeruginosa. Front Microbiol 2011; 2:89. [PMID: 21833328 PMCID: PMC3153048 DOI: 10.3389/fmicb.2011.00089] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2011] [Accepted: 04/13/2011] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen that is particularly problematic in the healthcare setting where it is a frequent cause of pneumonia, bloodstream, and urinary tract infections. An important determinant of P. aeruginosa virulence is a type III secretion system (T3SS). T3SS-dependent intoxication is a complex process that minimally requires binding of P. aeruginosa to host cells, injection of the cytotoxic effector proteins through the host cell plasma membrane, and induction of T3SS gene expression. The latter process, referred to as contact-dependent expression, involves a well-characterized regulatory cascade that activates T3SS gene expression in response to host cell contact. Although host cell contact is a primary activating signal for T3SS gene expression, the involvement of multiple membrane-bound regulatory systems indicates that additional environmental signals also play a role in controlling expression of the T3SS. These regulatory systems coordinate T3SS gene expression with many other cellular activities including motility, mucoidy, polysaccharide production, and biofilm formation. The signals to which the organism responds are poorly understood but many seem to be coupled to the metabolic state of the cell and integrated within a master circuit that assimilates informational signals from endogenous and exogenous sources. Herein we review progress toward unraveling this complex circuitry, provide analysis of the current knowledge gaps, and highlight potential areas for future studies. Complete understanding of the regulatory networks that control T3SS gene expression will maximize opportunities for the development of strategies to treat P. aeruginosa infections.
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Affiliation(s)
- Manisha R Diaz
- Department of Microbiology, University of Iowa Iowa City, IA, USA
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