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Paquette AR, Payne SR, McKay GA, Brazeau-Henrie JT, Darnowski MG, Kammili A, Bernal F, Mah TF, Gruenheid S, Nguyen D, Boddy CN. RpoN-Based stapled peptides with improved DNA binding suppress Pseudomonas aeruginosa virulence. RSC Med Chem 2022; 13:445-455. [PMID: 35647551 PMCID: PMC9020619 DOI: 10.1039/d1md00371b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Accepted: 02/02/2022] [Indexed: 11/21/2022] Open
Abstract
Stapled peptides have the ability to mimic α-helices involved in protein binding and have proved to be effective pharmacological agents for disrupting protein-protein interactions. DNA-binding proteins such as transcription factors bind their cognate DNA sequences via an α-helix interacting with the major groove of DNA. We previously developed a stapled peptide based on the bacterial alternative sigma factor RpoN capable of binding the RpoN DNA promoter sequence and inhibiting RpoN-mediated expression in Escherichia coli. We have elucidated a structure-activity relationship for DNA binding by this stapled peptide, improving DNA binding affinity constants in the high nM range. Lead peptides were shown to have low toxicity as determined by their low hemolytic activity at 100 μM and were shown to have anti-virulence activity in a Galleria mellonella model of Pseudomonas aeruginosa infection. These findings support further preclinical development of stapled peptides as antivirulence agents targeting P. aeruginosa.
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Affiliation(s)
- André R. Paquette
- Department of Chemistry and Biomolecular Sciences, University of OttawaOttawaONK1N 6N5 Canada
| | - Sterling R. Payne
- Laboratory of Protein Dynamics and Signaling, National Cancer Institute, National Institutes of HealthFrederickMD 21702USA
| | - Geoffrey A. McKay
- Meakins-Christie Laboratories, Research Institute of the McGill University Health CentreMontrealQuebec H4A 3J1Canada
| | | | - Micheal G. Darnowski
- Department of Chemistry and Biomolecular Sciences, University of OttawaOttawaONK1N 6N5 Canada
| | - Anitha Kammili
- Department of Chemistry and Biomolecular Sciences, University of Ottawa Ottawa ON K1N 6N5 Canada
| | - Federico Bernal
- Laboratory of Protein Dynamics and Signaling, National Cancer Institute, National Institutes of HealthFrederickMD 21702USA
| | - Thien-Fah Mah
- Department of Biochemistry, Microbiology, and Immunology, University of OttawaOttawaONK1H 8M5Canada
| | | | - Dao Nguyen
- Meakins-Christie Laboratories, Research Institute of the McGill University Health CentreMontrealQuebec H4A 3J1Canada,Department of Medicine, McGill UniversityMontrealQuebec H4A 3J1Canada
| | - Christopher N. Boddy
- Department of Chemistry and Biomolecular Sciences, University of OttawaOttawaONK1N 6N5 Canada
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2
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A Role for the RNA Polymerase Gene Specificity Factor σ 54 in the Uniform Colony Growth of Uropathogenic Escherichia coli. J Bacteriol 2022; 204:e0003122. [PMID: 35357162 PMCID: PMC9017345 DOI: 10.1128/jb.00031-22] [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] [Indexed: 11/20/2022] Open
Abstract
The canonical function of a bacterial sigma (σ) factor is to determine the gene specificity of the RNA polymerase (RNAP). In several diverse bacterial species, the σ54 factor uniquely confers distinct functional and regulatory properties on the RNAP. A hallmark feature of the σ54-RNAP is the obligatory requirement for an activator ATPase to allow transcription initiation. Different activator ATPases couple diverse environmental cues to the σ54-RNAP to mediate adaptive changes in gene expression. Hence, the genes that rely upon σ54 for their transcription have a wide range of different functions suggesting that the repertoire of functions performed by genes, directly or indirectly affected by σ54, is not yet exhaustive. By comparing the growth patterns of prototypical enteropathogenic, uropathogenic, and nonpathogenic Escherichia coli strains devoid of σ54, we uncovered that the absence of σ54 results in two differently sized colonies that appear at different times specifically in the uropathogenic E. coli (UPEC) strain. Notably, UPEC bacteria devoid of individual activator ATPases of the σ54-RNAP do not phenocopy the σ54 mutant strain. Thus, it seems that σ54’s role as a determinant of uniform colony appearance in UPEC bacteria represents a putative non-canonical function of σ54 in regulating genetic information flow. IMPORTANCE RNA synthesis is the first step of gene expression. The multisubunit RNA polymerase (RNAP) is the central enzyme responsible for RNA synthesis in bacteria. The dissociable sigma (σ) factor subunit directs the RNAP to different sets of genes to allow their expression in response to various cellular needs. Of the seven σ factors in Escherichia coli and related bacteria, σ54 exists in a class of its own. This study has uncovered that σ54 is a determinant of the uniform growth of uropathogenic E. coli on solid media. This finding suggests a role for this σ54 in gene regulation that extends beyond its known function as an RNAP gene specificity factor.
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3
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Allsopp LP, Collins ACZ, Hawkins E, Wood TE, Filloux A. RpoN/Sfa2-dependent activation of the Pseudomonas aeruginosa H2-T6SS and its cognate arsenal of antibacterial toxins. Nucleic Acids Res 2021; 50:227-243. [PMID: 34928327 PMCID: PMC8855297 DOI: 10.1093/nar/gkab1254] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Revised: 11/26/2021] [Accepted: 12/16/2021] [Indexed: 12/13/2022] Open
Abstract
Pseudomonas aeruginosa uses three type six secretion systems
(H1-, H2- and H3-T6SS) to manipulate its environment, subvert host cells and for
microbial competition. These T6SS machines are loaded with a variety of
effectors/toxins, many being associated with a specific VgrG. How P.
aeruginosa transcriptionally coordinates the main T6SS clusters and
the multiple vgrG islands spread through the genome is unknown.
Here we show an unprecedented level of control with RsmA repressing most known
T6SS-related genes. Moreover, each of the H2- and H3-T6SS clusters encodes a
sigma factor activator (SFA) protein
called, Sfa2 and Sfa3, respectively. SFA proteins are enhancer binding proteins
necessary for the sigma factor RpoN. Using a combination of RNA-seq, ChIP-seq
and molecular biology approaches, we demonstrate that RpoN coordinates the T6SSs
of P. aeruginosa by activating the H2-T6SS but repressing the
H1- and H3-T6SS. Furthermore, RpoN and Sfa2 control the expression of the
H2-T6SS-linked VgrGs and their effector arsenal to enable very effective
interbacterial killing. Sfa2 is specific as Sfa3 from the H3-T6SS cannot
complement loss of Sfa2. Our study further delineates the regulatory mechanisms
that modulate the deployment of an arsenal of T6SS effectors likely enabling
P. aeruginosa to adapt to a range of environmental
conditions.
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Affiliation(s)
- Luke P Allsopp
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, UK.,National Heart and Lung Institute, Imperial College London, London, UK
| | - Alice C Z Collins
- National Heart and Lung Institute, Imperial College London, London, UK
| | - Eleanor Hawkins
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, UK
| | - Thomas E Wood
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, UK
| | - Alain Filloux
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, UK
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4
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Yu C, Yang F, Xue D, Wang X, Chen H. The Regulatory Functions of σ 54 Factor in Phytopathogenic Bacteria. Int J Mol Sci 2021; 22:ijms222312692. [PMID: 34884502 PMCID: PMC8657755 DOI: 10.3390/ijms222312692] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 11/16/2021] [Accepted: 11/22/2021] [Indexed: 12/24/2022] Open
Abstract
σ54 factor (RpoN), a type of transcriptional regulatory factor, is widely found in pathogenic bacteria. It binds to core RNA polymerase (RNAP) and regulates the transcription of many functional genes in an enhancer-binding protein (EBP)-dependent manner. σ54 has two conserved functional domains: the activator-interacting domain located at the N-terminal and the DNA-binding domain located at the C-terminal. RpoN directly binds to the highly conserved sequence, GGN10GC, at the −24/−12 position relative to the transcription start site of target genes. In general, bacteria contain one or two RpoNs but multiple EBPs. A single RpoN can bind to different EBPs in order to regulate various biological functions. Thus, the overlapping and unique regulatory pathways of two RpoNs and multiple EBP-dependent regulatory pathways form a complex regulatory network in bacteria. However, the regulatory role of RpoN and EBPs is still poorly understood in phytopathogenic bacteria, which cause economically important crop diseases and pose a serious threat to world food security. In this review, we summarize the current knowledge on the regulatory function of RpoN, including swimming motility, flagella synthesis, bacterial growth, type IV pilus (T4Ps), twitching motility, type III secretion system (T3SS), and virulence-associated phenotypes in phytopathogenic bacteria. These findings and knowledge prove the key regulatory role of RpoN in bacterial growth and pathogenesis, as well as lay the groundwork for further elucidation of the complex regulatory network of RpoN in bacteria.
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Affiliation(s)
- Chao Yu
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China; (C.Y.); (F.Y.)
| | - Fenghuan Yang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China; (C.Y.); (F.Y.)
| | - Dingrong Xue
- National Engineering Laboratory of Grain Storage and Logistics, Academy of National Food and Strategic Reserves Administration, No. 11 Baiwanzhuang Street, Xicheng District, Beijing 100037, China;
| | - Xiuna Wang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China;
| | - Huamin Chen
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China; (C.Y.); (F.Y.)
- Correspondence:
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5
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Shimada T, Furuhata S, Ishihama A. Whole set of constitutive promoters for RpoN sigma factor and the regulatory role of its enhancer protein NtrC in Escherichia coli K-12. Microb Genom 2021; 7. [PMID: 34787538 PMCID: PMC8743547 DOI: 10.1099/mgen.0.000653] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The promoter selectivity of Escherichia coli RNA polymerase (RNAP) is determined by its promoter-recognition sigma subunit. The model prokaryote E. coli K-12 contains seven species of the sigma subunit, each recognizing a specific set of promoters. Using genomic SELEX (gSELEX) screening in vitro, we identified the whole set of ‘constitutive’ promoters recognized by the reconstituted RNAP holoenzyme alone, containing RpoD (σ70), RpoS (σ38), RpoH (σ32), RpoF (σ28) or RpoE (σ24), in the absence of other supporting regulatory factors. In contrast, RpoN sigma (σ54), involved in expression of nitrogen-related genes and also other cellular functions, requires an enhancer (or activator) protein, such as NtrC, for transcription initiation. In this study, a series of gSELEX screenings were performed to search for promoters recognized by the RpoN RNAP holoenzyme in the presence and absence of the major nitrogen response enhancer NtrC, the best-characterized enhancer. Based on the RpoN holoenzyme-binding sites, a total of 44 to 61 putative promoters were identified, which were recognized by the RpoN holoenzyme alone. In the presence of the enhancer NtrC, the recognition target increased to 61–81 promoters. Consensus sequences of promoters recognized by RpoN holoenzyme in the absence and presence of NtrC were determined. The promoter activity of a set of NtrC-dependent and -independent RpoN promoters was verified in vivo under nitrogen starvation, in the presence and absence of RpoN and/or NtrC. The promoter activity of some RpoN-recognized promoters increased in the absence of RpoN or NtrC, supporting the concept that the promoter-bound NtrC-enhanced RpoN holoenzyme functions as a repressor against RpoD holoenzyme. Based on our findings, we propose a model in which the RpoN holoenzyme fulfils the dual role of repressor and transcriptase for the same set of genes. We also propose that the promoter recognized by RpoN holoenzyme in the absence of enhancers is the ‘repressive’ promoter. The presence of high-level RpoN sigma in growing E. coli K-12 in rich medium may be related to the repression role of a set of genes needed for the utilization of ammonia as a nitrogen source in poor media. The list of newly identified regulatory targets of RpoN provides insight into E. coli survival under nitrogen-depleted conditions in nature.
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Affiliation(s)
- Tomohiro Shimada
- School of Agriculture, Meiji University, Kawasaki, Kanagawa, Japan
| | - Shun Furuhata
- School of Agriculture, Meiji University, Kawasaki, Kanagawa, Japan
| | - Akira Ishihama
- Micro-Nanotechnology Research Center, Hosei University, Koganei, Tokyo, Japan
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6
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Regulatory small RNA, Qrr2 is expressed independently of sigma factor-54 and can function as the sole Qrr sRNA to control quorum sensing in Vibrio parahaemolyticus. J Bacteriol 2021; 204:e0035021. [PMID: 34633869 DOI: 10.1128/jb.00350-21] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacterial cells alter gene expression in response to changes in population density in a process called quorum sensing (QS). In Vibrio harveyi, LuxO, a low cell density activator of sigma factor-54 (RpoN), is required for transcription of five non-coding regulatory sRNAs, Qrr1-Qrr5, which each repress translation of the master QS regulator LuxR. Vibrio parahaemolyticus, the leading cause of bacterial seafood-borne gastroenteritis, also contains five Qrr sRNAs that control OpaR (the LuxR homolog), controlling capsule polysaccharide (CPS), motility, and metabolism. We show that in a ΔluxO deletion mutant, opaR was de-repressed and CPS and biofilm were produced. However, in a ΔrpoN mutant, opaR was repressed, no CPS was produced, and less biofilm production was observed compared to wild type. To determine why opaR was repressed, expression analysis in ΔluxO showed all five qrr genes were repressed, while in ΔrpoN the qrr2 gene was significantly de-repressed. Reporter assays and mutant analysis showed Qrr2 sRNA can act alone to control OpaR. Bioinformatics analysis identified a sigma-70 (RpoD) -35 -10 promoter overlapping the canonical sigma-54 (RpoN) -24 -12 promoter in the qrr2 regulatory region. The qrr2 sigma-70 promoter element was also present in additional Vibrio species indicating it is widespread. Mutagenesis of the sigma-70 -10 promoter site in the ΔrpoN mutant background, resulted in repression of qrr2. Analysis of qrr quadruple deletion mutants, in which only a single qrr gene is present, showed that only Qrr2 sRNA can act independently to regulate opaR. Mutant and expression data also demonstrated that RpoN and the global regulator, Fis, act additively to repress qrr2. Our data has uncovered a new mechanism of qrr expression and shows that Qrr2 sRNA is sufficient for OpaR regulation. Importance The quorum sensing non-coding sRNAs are present in all Vibrio species but vary in number and regulatory roles among species. In the Harveyi clade, all species contain five qrr genes, and in V. harveyi these are transcribed by sigma-54 and are additive in function. In the Cholerae clade, four qrr genes are present, and in V. cholerae the qrr genes are redundant in function. In V. parahaemolyticus, qrr2 is controlled by two overlapping promoters. In an rpoN mutant, qrr2 is transcribed from a sigma-70 promoter that is present in all V. parahaemolyticus strains and in other species of the Harveyi clade suggesting a conserved mechanism of regulation. Qrr2 sRNA can function as the sole Qrr sRNA to control OpaR.
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7
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Mejía-Almonte C, Busby SJW, Wade JT, van Helden J, Arkin AP, Stormo GD, Eilbeck K, Palsson BO, Galagan JE, Collado-Vides J. Redefining fundamental concepts of transcription initiation in bacteria. Nat Rev Genet 2020; 21:699-714. [PMID: 32665585 PMCID: PMC7990032 DOI: 10.1038/s41576-020-0254-8] [Citation(s) in RCA: 82] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/29/2020] [Indexed: 12/15/2022]
Abstract
Despite enormous progress in understanding the fundamentals of bacterial gene regulation, our knowledge remains limited when compared with the number of bacterial genomes and regulatory systems to be discovered. Derived from a small number of initial studies, classic definitions for concepts of gene regulation have evolved as the number of characterized promoters has increased. Together with discoveries made using new technologies, this knowledge has led to revised generalizations and principles. In this Expert Recommendation, we suggest precise, updated definitions that support a logical, consistent conceptual framework of bacterial gene regulation, focusing on transcription initiation. The resulting concepts can be formalized by ontologies for computational modelling, laying the foundation for improved bioinformatics tools, knowledge-based resources and scientific communication. Thus, this work will help researchers construct better predictive models, with different formalisms, that will be useful in engineering, synthetic biology, microbiology and genetics.
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Affiliation(s)
- Citlalli Mejía-Almonte
- Programa de Genómica Computacional, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Morelos, Cuernavaca, México
| | | | - Joseph T Wade
- Division of Genetics, Wadsworth Center, New York State Department of Health, Albany, NY, USA
| | - Jacques van Helden
- Aix-Marseille University, INSERM UMR S 1090, Theory and Approaches of Genome Complexity (TAGC), Marseille, France
- CNRS, Institut Français de Bioinformatique, IFB-core, UMS 3601, Evry, France
| | - Adam P Arkin
- Department of Bioengineering, University of California, Berkeley, Berkeley, CA, USA
| | - Gary D Stormo
- Department of Genetics, Washington University School of Medicine, St Louis, MO, USA
| | - Karen Eilbeck
- Department of Biomedical Informatics, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Bernhard O Palsson
- Department of Bioengineering, University of California, San Diego, La Jolla, CA, USA
| | - James E Galagan
- Department of Biomedical Engineering, Boston University, Boston, MA, USA
| | - Julio Collado-Vides
- Programa de Genómica Computacional, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Morelos, Cuernavaca, México.
- Department of Biomedical Engineering, Boston University, Boston, MA, USA.
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8
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Bernal P, Murillo-Torres M, Allsopp LP. Integrating signals to drive type VI secretion system killing. Environ Microbiol 2020; 22:4520-4523. [PMID: 32990336 DOI: 10.1111/1462-2920.15255] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Accepted: 09/25/2020] [Indexed: 11/29/2022]
Affiliation(s)
- Patricia Bernal
- Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Seville, Spain
| | - Marina Murillo-Torres
- Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Seville, Spain.,National Heart and Lung Institute, Imperial College London, London, UK
| | - Luke P Allsopp
- National Heart and Lung Institute, Imperial College London, London, UK
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9
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Li K, Wu G, Liao Y, Zeng Q, Wang H, Liu F. RpoN1 and RpoN2 play different regulatory roles in virulence traits, flagellar biosynthesis, and basal metabolism in Xanthomonas campestris. MOLECULAR PLANT PATHOLOGY 2020; 21:907-922. [PMID: 32281725 PMCID: PMC7280030 DOI: 10.1111/mpp.12938] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 03/18/2020] [Accepted: 03/18/2020] [Indexed: 05/08/2023]
Abstract
Homologous regulatory factors are widely present in bacteria, but whether homologous regulators synergistically or differentially regulate different biological functions remains mostly unknown. Here, we report that the homologous regulators RpoN1 and RpoN2 of the plant pathogen Xanthomonas campestris pv. campestris (Xcc) play different regulatory roles with respect to virulence traits, flagellar biosynthesis, and basal metabolism. RpoN2 directly regulated Xcc fliC and fliQ to modulate flagellar synthesis in X. campestris, thus affecting the swimming motility of X. campestris. Mutation of rpoN2 resulted in reduced production of biofilms and extracellular polysaccharides in Xcc. These defects may together cause reduced virulence of the rpoN2 mutant against the host plant. Moreover, we demonstrated that RpoN1 could regulate branched-chain fatty acid production and modulate the synthesis of diffusible signal factor family quorum sensing signals. Although RpoN1 and RpoN2 are homologues, the regulatory roles and biological functions of these proteins were not interchangeable. Overall, our report provides new insights into the two different molecular roles that form the basis for the transcriptional specialization of RpoN homologues.
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Affiliation(s)
- Kaihuai Li
- College of Plant ProtectionNanjing Agricultural UniversityNanjingChina
| | - Guichun Wu
- Institute of Plant ProtectionJiangsu Academy of Agricultural SciencesNanjingChina
| | - Yuling Liao
- Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural OrganismsCollege of Life SciencesSouth China Agricultural UniversityGuangzhouChina
| | - Quan Zeng
- Department of Plant Pathology and EcologyThe Connecticut Agricultural Experiment StationNew HavenCTUSA
| | - Haihong Wang
- Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural OrganismsCollege of Life SciencesSouth China Agricultural UniversityGuangzhouChina
| | - Fengquan Liu
- College of Plant ProtectionNanjing Agricultural UniversityNanjingChina
- Institute of Plant ProtectionJiangsu Academy of Agricultural SciencesNanjingChina
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10
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Contribution of σ 70 and σ N Factors to Expression of Class II pilE in Neisseria meningitidis. J Bacteriol 2019; 201:JB.00170-19. [PMID: 31331980 PMCID: PMC6755734 DOI: 10.1128/jb.00170-19] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2019] [Accepted: 07/16/2019] [Indexed: 02/06/2023] Open
Abstract
Neisseria meningitidis expresses multicomponent organelles called type four pili (Tfp), which are key virulence factors required for attachment to human cells during carriage and disease. Pilin (PilE) is the main component of Tfp, and N. meningitidis isolates either have a class I pilE locus and express pilins that undergo antigenic variation or have a class II pilE locus and express invariant pilins. The transcriptional regulation of class I pilE has been studied in both N. meningitidis and Neisseria gonorrhoeae, while the control of expression of class II pilE has been elucidated in the nonpathogenic species Neisseria elongata However, the factors that govern the regulation of the class II pilE gene in N. meningitidis are not known. In this work, we have bioinformatically and experimentally identified the class II pilE promoter. We confirmed the presence of conserved σ70 and σN-dependent promoters upstream of pilE in a collection of meningococcal genomes and demonstrated that class II pilE expression initiates from the σ70 family-dependent promoter. By deletion or overexpression of sigma factors, we showed that σN, σH, and σE do not affect class II pilin expression. These findings are consistent with a role of the housekeeping σD in expression of this important component of Tfp. Taken together, our data indicate that the σ-dependent network responsible for the expression of class II pilE has been selected to maintain pilE expression, consistent with the essential roles of Tfp in colonization and pathogenesis.IMPORTANCE The type four pilus (Tfp) of Neisseria meningitidis contributes to fundamental processes such as adhesion, transformation, and disease pathology. Meningococci express one of two distinct classes of Tfp (class I or class II), which can be distinguished antigenically or by the major subunit (pilE) locus and its genetic context. The factors that govern transcription of the class II pilE gene are not known, even though it is present in isolates that cause epidemic disease. Here we show that the transcription of class II pilE is maintained throughout growth and under different stress conditions and is driven by a σ70-dependent promoter. This is distinct from Tfp regulation in nonpathogenic Neisseria spp. and may confer an advantage during host-cell interaction and infection.
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11
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Abstract
σN (also σ54) is an alternative sigma factor subunit of the RNA polymerase complex that regulates the expression of genes from many different ontological groups. It is broadly conserved in the Eubacteria with major roles in nitrogen metabolism, membrane biogenesis, and motility. σN is encoded as the first gene of a five-gene operon including rpoN (σN), ptsN, hpf, rapZ, and npr that has been genetically retained among species of Escherichia, Shigella, and Salmonella. In an increasing number of bacteria, σN has been implicated in the control of genes essential to pathogenic behavior, including those involved in adherence, secretion, immune subversion, biofilm formation, toxin production, and resistance to both antimicrobials and biological stressors. For most pathogens how this is achieved is unknown. In enterohemorrhagic Escherichia coli (EHEC) O157, Salmonella enterica, and Borrelia burgdorferi, regulation of virulence by σN requires another alternative sigma factor, σS, yet the model by which σN-σS virulence regulation is predicted to occur is varied in each of these pathogens. In this review, the importance of σN to bacterial pathogenesis is introduced, and common features of σN-dependent virulence regulation discussed. Emphasis is placed on the molecular mechanisms underlying σN virulence regulation in E. coli O157. This includes a review of the structure and function of regulatory pathways connecting σN to virulence expression, predicted input signals for pathway stimulation, and the role for cognate σN activators in initiation of gene systems determining pathogenic behavior.
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12
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Abstract
Transcription initiation is highly regulated in bacterial cells, allowing adaptive gene regulation in response to environment cues. One class of promoter specificity factor called sigma54 enables such adaptive gene expression through its ability to lock the RNA polymerase down into a state unable to melt out promoter DNA for transcription initiation. Promoter DNA opening then occurs through the action of specialized transcription control proteins called bacterial enhancer-binding proteins (bEBPs) that remodel the sigma54 factor within the closed promoter complexes. The remodelling of sigma54 occurs through an ATP-binding and hydrolysis reaction carried out by the bEBPs. The regulation of bEBP self-assembly into typically homomeric hexamers allows regulated gene expression since the self-assembly is required for bEBP ATPase activity and its direct engagement with the sigma54 factor during the remodelling reaction. Crystallographic studies have now established that in the closed promoter complex, the sigma54 factor occupies the bacterial RNA polymerase in ways that will physically impede promoter DNA opening and the loading of melted out promoter DNA into the DNA-binding clefts of the RNA polymerase. Large-scale structural re-organizations of sigma54 require contact of the bEBP with an amino-terminal glutamine and leucine-rich sequence of sigma54, and lead to domain movements within the core RNA polymerase necessary for making open promoter complexes and synthesizing the nascent RNA transcript.
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13
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Novel DNA Binding and Regulatory Activities for σ 54 (RpoN) in Salmonella enterica Serovar Typhimurium 14028s. J Bacteriol 2017; 199:JB.00816-16. [PMID: 28373272 DOI: 10.1128/jb.00816-16] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2016] [Accepted: 03/27/2017] [Indexed: 01/13/2023] Open
Abstract
The variable sigma (σ) subunit of the bacterial RNA polymerase (RNAP) holoenzyme, which is responsible for promoter specificity and open complex formation, plays a strategic role in the response to environmental changes. Salmonella enterica serovar Typhimurium utilizes the housekeeping σ70 and five alternative sigma factors, including σ54 The σ54-RNAP differs from other σ-RNAP holoenzymes in that it forms a stable closed complex with the promoter and requires ATP hydrolysis by an activated cognate bacterial enhancer binding protein (bEBP) to transition to an open complex and initiate transcription. In S. Typhimurium, σ54-dependent promoters normally respond to one of 13 different bEBPs, each of which is activated under a specific growth condition. Here, we utilized a constitutively active, promiscuous bEBP to perform a genome-wide identification of σ54-RNAP DNA binding sites and the transcriptome of the σ54 regulon of S. Typhimurium. The position and context of many of the identified σ54 RNAP DNA binding sites suggest regulatory roles for σ54-RNAP that connect the σ54 regulon to regulons of other σ factors to provide a dynamic response to rapidly changing environmental conditions.IMPORTANCE The alternative sigma factor σ54 (RpoN) is required for expression of genes involved in processes with significance in agriculture, bioenergy production, bioremediation, and host-microbe interactions. The characterization of the σ54 regulon of the versatile pathogen S. Typhimurium has expanded our understanding of the scope of the σ54 regulon and how it links to other σ regulons within the complex regulatory network for gene expression in bacteria.
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Engl C, Schaefer J, Kotta-Loizou I, Buck M. Cellular and molecular phenotypes depending upon the RNA repair system RtcAB of Escherichia coli. Nucleic Acids Res 2016; 44:9933-9941. [PMID: 27402162 PMCID: PMC5175333 DOI: 10.1093/nar/gkw628] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Revised: 06/06/2016] [Accepted: 06/23/2016] [Indexed: 11/24/2022] Open
Abstract
RNA ligases function pervasively across the three kingdoms of life for RNA repair, splicing and can be stress induced. The RtcB protein (also HSPC117, C22orf28, FAAP and D10Wsu52e) is one such conserved ligase, involved in tRNA and mRNA splicing. However, its physiological role is poorly described, especially in bacteria. We now show in Escherichia coli bacteria that the RtcR activated rtcAB genes function for ribosome homeostasis involving rRNA stability. Expression of rtcAB is activated by agents and genetic lesions which impair the translation apparatus or may cause oxidative damage in the cell. Rtc helps the cell to survive challenges to the translation apparatus, including ribosome targeting antibiotics. Further, loss of Rtc causes profound changes in chemotaxis and motility. Together, our data suggest that the Rtc system is part of a previously unrecognized adaptive response linking ribosome homeostasis with basic cell physiology and behaviour.
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Affiliation(s)
- Christoph Engl
- Faculty of Natural Sciences, Division of Cell & Molecular Biology, Imperial College London, London SW7 2AZ, UK .,Institute for Global Food Security, Queen's University Belfast, Belfast BT9 7BL, UK
| | - Jorrit Schaefer
- Faculty of Natural Sciences, Division of Cell & Molecular Biology, Imperial College London, London SW7 2AZ, UK
| | - Ioly Kotta-Loizou
- Faculty of Natural Sciences, Division of Cell & Molecular Biology, Imperial College London, London SW7 2AZ, UK
| | - Martin Buck
- Faculty of Natural Sciences, Division of Cell & Molecular Biology, Imperial College London, London SW7 2AZ, UK
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15
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Wörmann ME, Horien CL, Johnson E, Liu G, Aho E, Tang CM, Exley RM. Neisseria cinerea isolates can adhere to human epithelial cells by type IV pilus-independent mechanisms. MICROBIOLOGY-SGM 2016; 162:487-502. [PMID: 26813911 DOI: 10.1099/mic.0.000248] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
In pathogenic Neisseria species the type IV pili (Tfp) are of primary importance in host-pathogen interactions. Tfp mediate initial bacterial attachment to cell surfaces and formation of microcolonies via pilus-pilus interactions. Based on genome analysis, many non-pathogenic Neisseria species are predicted to express Tfp, but aside from studies on Neisseria elongata, relatively little is known about the formation and function of pili in these organisms. Here, we have analysed pilin expression and the role of Tfp in Neisseria cinerea. This non-pathogenic species shares a close taxonomic relationship to the pathogen Neisseria meningitidis and also colonizes the human oropharyngeal cavity. Through analysis of non-pathogenic Neisseria genomes we identified two genes with homology to pilE, which encodes the major pilin of N. meningitidis. We show which of the two genes is required for Tfp expression in N. cinerea and that Tfp in this species are required for DNA competence, similar to other Neisseria. However, in contrast to the meningococcus, deletion of the pilin gene did not impact the association of N. cinerea to human epithelial cells, demonstrating that N. cinerea isolates can adhere to human epithelial cells by Tfp-independent mechanisms.
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Affiliation(s)
- Mirka E Wörmann
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK
| | - Corey L Horien
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK
| | - Errin Johnson
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK
| | - Guangyu Liu
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK
| | - Ellen Aho
- Department of Biology, Concordia College, Moorhead, MN, USA
| | - Christoph M Tang
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK
| | - Rachel M Exley
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK
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16
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Zhang N, Jovanovic G, McDonald C, Ces O, Zhang X, Buck M. Transcription Regulation and Membrane Stress Management in Enterobacterial Pathogens. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 915:207-30. [DOI: 10.1007/978-3-319-32189-9_13] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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17
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Bonocora RP, Smith C, Lapierre P, Wade JT. Genome-Scale Mapping of Escherichia coli σ54 Reveals Widespread, Conserved Intragenic Binding. PLoS Genet 2015; 11:e1005552. [PMID: 26425847 PMCID: PMC4591121 DOI: 10.1371/journal.pgen.1005552] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Accepted: 09/03/2015] [Indexed: 11/18/2022] Open
Abstract
Bacterial RNA polymerases must associate with a σ factor to bind promoter DNA and initiate transcription. There are two families of σ factor: the σ70 family and the σ54 family. Members of the σ54 family are distinct in their ability to bind promoter DNA sequences, in the context of RNA polymerase holoenzyme, in a transcriptionally inactive state. Here, we map the genome-wide association of Escherichia coli σ54, the archetypal member of the σ54 family. Thus, we vastly expand the list of known σ54 binding sites to 135. Moreover, we estimate that there are more than 250 σ54 sites in total. Strikingly, the majority of σ54 binding sites are located inside genes. The location and orientation of intragenic σ54 binding sites is non-random, and many intragenic σ54 binding sites are conserved. We conclude that many intragenic σ54 binding sites are likely to be functional. Consistent with this assertion, we identify three conserved, intragenic σ54 promoters that drive transcription of mRNAs with unusually long 5ʹ UTRs. Bacterial RNA polymerases must associate with a σ factor to bind to promoter DNA sequences upstream of genes and initiate transcription. There are two families of σ factor: σ70 and σ54. Members of the σ54 family are distinct from members of the σ70 family in their ability to bind promoter DNA sequences, in association with RNA polymerase, in a transcriptionally inactive state. We have determined positions in the Escherichia coli genome that are bound by σ54, the archetypal member of the σ54 family. Surprisingly, we identified 135 binding sites for σ54, a huge increase over the number of previously described sites. Our data suggest that there are more than 250 σ54 sites in total. Strikingly, most σ54 binding sites are located inside genes, whereas only one intragenic σ54 binding site has previously been described. The location and orientation of intragenic σ54 binding sites is non-random, and many intragenic σ54 binding sites are conserved in other bacterial species. We conclude that many intragenic σ54 binding sites are likely to be functional. Consistent with this notion, we identify three σ54 promoters in E. coli that are located inside genes but drive transcription of unusual mRNAs for the neighboring genes.
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Affiliation(s)
- Richard P. Bonocora
- Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
| | - Carol Smith
- Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
| | - Pascal Lapierre
- Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
| | - Joseph T. Wade
- Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
- Department of Biomedical Sciences, School of Public Health, University at Albany, Albany, New York, United States of America
- * E-mail:
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