1
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Vannini A, Pinatel E, Costantini PE, Pelliciari S, Roncarati D, Puccio S, De Bellis G, Scarlato V, Peano C, Danielli A. (Re)-definition of the holo- and apo-Fur direct regulons of Helicobacter pylori. J Mol Biol 2024; 436:168573. [PMID: 38626867 DOI: 10.1016/j.jmb.2024.168573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Revised: 04/09/2024] [Accepted: 04/10/2024] [Indexed: 04/28/2024]
Abstract
Iron homeostasis is a critical process for living organisms because this metal is an essential co-factor for fundamental biochemical activities, like energy production and detoxification, albeit its excess quickly leads to cell intoxication. The protein Fur (ferric uptake regulator) controls iron homeostasis in bacteria by switching from its apo- to holo-form as a function of the cytoplasmic level of ferrous ions, thereby modulating gene expression. The Helicobacter pylori HpFur protein has the rare ability to operate as a transcriptional commutator; apo- and holo-HpFur function as two different repressors with distinct DNA binding recognition properties for specific sets of target genes. Although the regulation of apo- and holo-HpFur in this bacterium has been extensively investigated, we propose a genome-wide redefinition of holo-HpFur direct regulon in H. pylori by integration of RNA-seq and ChIP-seq data, and a large extension of the apo-HpFur direct regulon. We show that in response to iron availability, new coding sequences, non-coding RNAs, toxin-antitoxin systems, and transcripts within open reading frames are directly regulated by apo- or holo-HpFur. These new targets and the more thorough validation and deeper characterization of those already known provide a complete and updated picture of the direct regulons of this two-faced transcriptional regulator.
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Affiliation(s)
- Andrea Vannini
- University of Bologna Department of Pharmacy and Biotechnology, Via Selmi 3, 40126 Bologna, Italy.
| | - Eva Pinatel
- Institute of Biomedical Technologies - National Research Council, Via Fratelli Cervi 93, 20054 Segrate (MI), Italy.
| | - Paolo Emidio Costantini
- University of Bologna Department of Pharmacy and Biotechnology, Via Selmi 3, 40126 Bologna, Italy.
| | - Simone Pelliciari
- Human Genetic Unit, Institute of Genetic and Cancer - University of Edinburgh, Crewe Road, Edinburgh EH4 2XU, UK.
| | - Davide Roncarati
- University of Bologna Department of Pharmacy and Biotechnology, Via Selmi 3, 40126 Bologna, Italy.
| | - Simone Puccio
- Institute of Genetics and Biomedical Research, UoS Milan - National Research Council, Via Manzoni 113, 20089 Rozzano (MI), Italy; Humanitas Clinical and Research Center, Via Manzoni 56, 20089 Rozzano (MI), Italy.
| | - Gianluca De Bellis
- Institute of Biomedical Technologies - National Research Council, Via Fratelli Cervi 93, 20054 Segrate (MI), Italy.
| | - Vincenzo Scarlato
- University of Bologna Department of Pharmacy and Biotechnology, Via Selmi 3, 40126 Bologna, Italy.
| | - Clelia Peano
- Institute of Genetics and Biomedical Research, UoS Milan - National Research Council, Via Manzoni 113, 20089 Rozzano (MI), Italy; Human Technopole, Via Rita Levi Montalcini 1, 20157 Milan, Italy.
| | - Alberto Danielli
- University of Bologna Department of Pharmacy and Biotechnology, Via Selmi 3, 40126 Bologna, Italy.
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2
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Wu S, Chen Y, Chen Z, Wei F, Zhou Q, Li P, Gu Q. Reactive oxygen species and gastric carcinogenesis: The complex interaction between Helicobacter pylori and host. Helicobacter 2023; 28:e13024. [PMID: 37798959 DOI: 10.1111/hel.13024] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 09/10/2023] [Accepted: 09/21/2023] [Indexed: 10/07/2023]
Abstract
Helicobacter pylori (H. pylori) is a highly successful human pathogen that colonizes stomach in around 50% of the global population. The colonization of bacterium induces an inflammatory response and a substantial rise in the production of reactive oxygen species (ROS) and reactive nitrogen species (RNS), mostly derived from host neutrophils and gastric epithelial cells, which play a crucial role in combating bacterial infections. However, H. pylori has developed various strategies to quench the deleterious effects of ROS, including the production of antioxidant enzymes, antioxidant proteins as well as blocking the generation of oxidants. The host's inability to eliminate H. pylori infection results in persistent ROS production. Notably, excessive ROS can disrupt the intracellular signal transduction and biological processes of the host, incurring chronic inflammation and cellular damage, such as DNA damage, lipid peroxidation, and protein oxidation. Markedly, the sustained inflammatory response and oxidative stress during H. pylori infection are major risk factor for gastric carcinogenesis. In this context, we summarize the literature on H. pylori infection-induced ROS production, the strategies used by H. pylori to counteract the host response, and subsequent host damage and gastric carcinogenesis.
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Affiliation(s)
- Shiying Wu
- Key Laboratory for Food Microbial Technology of Zhejiang Province, College of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou, China
| | - Yongqiang Chen
- Key Laboratory for Food Microbial Technology of Zhejiang Province, College of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou, China
| | - Ziqi Chen
- Key Laboratory for Food Microbial Technology of Zhejiang Province, College of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou, China
| | - Fangtong Wei
- Key Laboratory for Food Microbial Technology of Zhejiang Province, College of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou, China
| | - Qingqing Zhou
- Key Laboratory for Food Microbial Technology of Zhejiang Province, College of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou, China
| | - Ping Li
- Key Laboratory for Food Microbial Technology of Zhejiang Province, College of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou, China
| | - Qing Gu
- Key Laboratory for Food Microbial Technology of Zhejiang Province, College of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou, China
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3
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Loh JT, Struttmann EL, Favret N, Harvey ML, Pakala SB, Chopra A, McClain MS, Cover TL. A Positively Selected fur-R88H Mutation Enhances Helicobacter pylori Fitness in a High-Salt Environment and Alters Fur-Dependent Regulation of Gene Expression. Infect Immun 2023; 91:e0042022. [PMID: 36633416 DOI: 10.1128/iai.00420-22] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Both Helicobacter pylori infection and a high-salt diet are risk factors for gastric cancer. We previously showed that a mutation in fur (encoding the ferric uptake regulator variant Fur-R88H) was positively selected in H. pylori strains isolated from experimentally infected Mongolian gerbils receiving a high-salt diet. In the present study, we report that continuous H. pylori growth in high-salt conditions in vitro also leads to positive selection of the fur-R88H mutation. Competition experiments with strains containing wild-type fur or fur-R88H, each labeled with unique nucleotide barcodes, showed that the fur-R88H mutation enhances H. pylori fitness under high-salt conditions but reduces H. pylori fitness under routine culture conditions. The fitness advantage of the fur-R88H mutant under high-salt conditions was abrogated by the addition of supplemental iron. To test the hypothesis that the fur-R88H mutation alters the regulatory properties of Fur, we compared the transcriptional profiles of strains containing wild-type fur or fur-R88H. Increased transcript levels of fecA2, which encodes a predicted TonB-dependent outer membrane transporter, were detected in the fur-R88H variant compared to those in the strain containing wild-type fur under both high-salt and routine conditions. Competition experiments showed that fecA2 contributes to H. pylori fitness under both high-salt and routine conditions. These results provide new insights into mechanisms by which the fur-R88H mutation confers a selective advantage to H. pylori in high-salt environments.
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4
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Vannini A, Roncarati D, D'Agostino F, Antoniciello F, Scarlato V. Insights into the Orchestration of Gene Transcription Regulators in Helicobacter pylori. Int J Mol Sci 2022; 23. [PMID: 36430169 DOI: 10.3390/ijms232213688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 10/31/2022] [Accepted: 11/04/2022] [Indexed: 11/09/2022] Open
Abstract
Bacterial pathogens employ a general strategy to overcome host defenses by coordinating the virulence gene expression using dedicated regulatory systems that could raise intricate networks. During the last twenty years, many studies of Helicobacter pylori, a human pathogen responsible for various stomach diseases, have mainly focused on elucidating the mechanisms and functions of virulence factors. In parallel, numerous studies have focused on the molecular mechanisms that regulate gene transcription to attempt to understand the physiological changes of the bacterium during infection and adaptation to the environmental conditions it encounters. The number of regulatory proteins deduced from the genome sequence analyses responsible for the correct orchestration of gene transcription appears limited to 14 regulators and three sigma factors. Furthermore, evidence is accumulating for new and complex circuits regulating gene transcription and H. pylori virulence. Here, we focus on the molecular mechanisms used by H. pylori to control gene transcription as a function of the principal environmental changes.
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Kelley BR, Lu J, Haley KP, Gaddy JA, Johnson JG. Metal homeostasis in pathogenic Epsilonproteobacteria: mechanisms of acquisition, efflux, and regulation. Metallomics 2021; 13:mfaa002. [PMID: 33570133 PMCID: PMC8043183 DOI: 10.1093/mtomcs/mfaa002] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 11/25/2020] [Accepted: 12/03/2020] [Indexed: 12/14/2022]
Abstract
Epsilonproteobacteria are a diverse class of eubacteria within the Proteobacteria phylum that includes environmental sulfur-reducing bacteria and the human pathogens, Campylobacter jejuni and Helicobacter pylori. These pathogens infect and proliferate within the gastrointestinal tracts of multiple animal hosts, including humans, and cause a variety of disease outcomes. While infection of these hosts provides nutrients for the pathogenic Epsilonproteobacteria, many hosts have evolved a variety of strategies to either sequester metals from the invading pathogen or exploit the toxicity of metals and drive their accumulation as an antimicrobial strategy. As a result, C. jejuni and H. pylori have developed mechanisms to sense changes in metal availability and regulate their physiology in order to respond to either metal limitation or accumulation. In this review, we will discuss the challenges of metal availability at the host-pathogen interface during infection with C. jejuni and H. pylori and describe what is currently known about how these organisms alter their gene expression and/or deploy bacterial virulence factors in response to these environments.
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Affiliation(s)
- Brittni R Kelley
- Department of Microbiology, University of Tennessee, Knoxville, TN, USA
| | - Jacky Lu
- Department of Pathology, Microbiology and Immunology, Vanderbilt University, Nashville, TN, USA
| | - Kathryn P Haley
- Department of Biology, Grand Valley State University, Grand Rapids, MI, USA
| | - Jennifer A Gaddy
- Department of Pathology, Microbiology and Immunology, Vanderbilt University, Nashville, TN, USA
- Tennessee Valley Healthcare Systems, Department of Veterans Affairs, Nashville, TN, USA
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
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6
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Price EE, Boyd JM. Genetic Regulation of Metal Ion Homeostasis in Staphylococcus aureus. Trends Microbiol 2020; 28:821-31. [PMID: 32381454 DOI: 10.1016/j.tim.2020.04.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 04/01/2020] [Accepted: 04/02/2020] [Indexed: 12/16/2022]
Abstract
The acquisition of metal ions and the proper maturation of holo-metalloproteins are essential processes for all organisms. However, metal ion homeostasis is a double-edged sword. A cytosolic accumulation of metal ions can lead to mismetallation of proteins and cell death. Therefore, maintenance of proper concentrations of intracellular metals is essential for cell fitness and pathogenesis. Staphylococcus aureus, like all bacterial pathogens, uses transcriptional metalloregulatory proteins to aid in the detection and the genetic response to changes in metal ion concentrations. Herein, we review the mechanisms by which S. aureus senses and responds to alterations in the levels of cellular zinc, iron, heme, and copper. The interplay between metal ion sensing and metal-dependent expression of virulence factors is also discussed.
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7
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Guo Y, Guan C, Wan H, Zhang Z, Li H, Sun H, Xia W. Inactivation of NikR from Helicobacter pylori by a bismuth drug. J Inorg Biochem 2019; 196:110685. [PMID: 30999221 DOI: 10.1016/j.jinorgbio.2019.03.025] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 03/21/2019] [Accepted: 03/28/2019] [Indexed: 01/18/2023]
Abstract
The NikR protein is an essential DNA regulator of Helicobacter pylori, a human pathogen, which infects almost half of the world's population. Herein, we comprehensively characterized the interaction of a bismuth drug with Helicobacter pylori NikR. We show that Bi(III) can occupy the high-affinity Ni(II) site of NikR. The highly-conserved residue Cys107 at this site is critical for Bi(III) binding. Importantly, such a binding disassembles physiologically functional NikR tetramer into inactive dimer, leading to abrogation of the DNA-binding capability of NikR. Bi(III)-binding also significantly disturbs regulatory function of Helicobacter pylori NikR in vivo. Therefore, NikR might serve as a potential intracellular target of a bismuth drug.
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Affiliation(s)
- Yu Guo
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry, Sun Yat-sen University, Guangzhou, China, 510275
| | - Chujun Guan
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry, Sun Yat-sen University, Guangzhou, China, 510275
| | - Heiyu Wan
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry, Sun Yat-sen University, Guangzhou, China, 510275
| | - Zhengrui Zhang
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry, Sun Yat-sen University, Guangzhou, China, 510275
| | - Hongyan Li
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China
| | - Hongzhe Sun
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
| | - Wei Xia
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry, Sun Yat-sen University, Guangzhou, China, 510275.
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8
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Abstract
Helicobacter pylori is a human pathogen that infects the stomach, where it experiences variable pH. To survive the acidic gastric conditions, H. pylori produces large quantities of urease, a nickel enzyme that hydrolyzes urea to ammonia, which neutralizes the local environment. One of the regulators of urease expression in H. pylori is HpNikR, a nickel-responsive transcription factor. Here we show that HpNikR also regulates urease expression in response to changes in pH, linking acid adaptation and nickel homeostasis. Upon measuring the cytosolic pH of H. pylori exposed to an external pH of 2, similar to the acidic shock conditions that occur in the human stomach, a significant drop in internal pH was observed. This decrease in internal pH resulted in HpNikR-dependent activation of ureA transcription. Furthermore, analysis of a slate of H. pylori genes encoding other acid adaptation or nickel homeostasis components revealed HpNikR-dependent regulation in response to acid shock. This regulation was consistent with pH-dependent DNA binding to the corresponding promoter sequences observed in vitro with purified HpNikR. These results demonstrate that HpNikR can directly respond to changes in cytosolic pH during acid acclimation and illustrate the exquisitely coordinated regulatory networks that support H. pylori infections in the harsh environment of the human stomach.
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Affiliation(s)
- Michael D Jones
- Department of Chemistry, University of Toronto, Toronto, ON M5S 3H6, Canada
| | - Yanjie Li
- Department of Chemistry, University of Toronto, Toronto, ON M5S 3H6, Canada
| | - Deborah B Zamble
- Department of Chemistry, University of Toronto, Toronto, ON M5S 3H6, Canada;
- Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
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9
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Kato S, Osaki T, Kamiya S, Zhang XS, Blaser MJ. Helicobacter pylori sabA gene is associated with iron deficiency anemia in childhood and adolescence. PLoS One 2017; 12:e0184046. [PMID: 28854239 PMCID: PMC5576686 DOI: 10.1371/journal.pone.0184046] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Accepted: 08/17/2017] [Indexed: 12/16/2022] Open
Abstract
Background Gastric Helicobacter pylori colonization leads to iron deficiency anemia (IDA), especially in children and adolescents. However the pathogenesis is poorly understood. Objective We sought to identify specific H. pylori genes involved in IDA development, by comparing bacterial genome-wide expression profiling in patients affected or not. Methods H. pylori were isolated from four children with IDA and four from matched controls without IDA. Based on these isolates, cDNA microarrays under iron-replete or depleted conditions were systematically performed to compare gene expression profiles at the whole genome level. Real-time reverse-transcription (RT-) PCR and protein assays were performed for further assessing the profile differentiation of the identified H. pylori IDA-associated genes. Results We identified 29 and 11 genes with significantly higher or lower expression in the IDA isolates compared to non-IDA isolates, respectively. Especially notable were higher expression of sabA gene encoding sialic acid-binding adhesin in the IDA isolates, which was confirmed by real-time RT-PCR study. Moreover, iron-depletion in vitro led to up-regulation of fecA1 and frpB1 genes and down-regulation of pfr, as predicted. Known iron-regulated genes such as fur, pfr, fecA, and feoB did not significantly differ between both groups. The IDA isolates had significantly higher expression of vacuolating cytotoxin gene vacA than non-IDA isolates, consistent with the results of VacA protein assays. There were no significant differences in bacterial growth value between IDA and non-IDA isolates. Conclusions It is likely that H. pylori carrying high expression of sabA causes IDA, especially in children and adolescents who have increased daily iron demand. In addition, it is possible that several host-interactive genes, including vacA, may play a synergistic role for sabA in IDA development.
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Affiliation(s)
- Seiichi Kato
- Department of Pediatrics, Tohoku University School of Medicine, Sendai, Japan
- Department of Infectious Diseases, Kyorin University School of Medicine, Mitaka, Japan
- * E-mail:
| | - Takako Osaki
- Department of Infectious Diseases, Kyorin University School of Medicine, Mitaka, Japan
| | - Shigeru Kamiya
- Department of Infectious Diseases, Kyorin University School of Medicine, Mitaka, Japan
| | - Xue-Song Zhang
- Departments of Medicine and Microbiology, New York University School of Medicine, New York, NY, United States of America
| | - Martin J. Blaser
- Departments of Medicine and Microbiology, New York University School of Medicine, New York, NY, United States of America
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Haley KP, Gaddy JA. Nutrition and Helicobacter pylori: Host Diet and Nutritional Immunity Influence Bacterial Virulence and Disease Outcome. Gastroenterol Res Pract 2016; 2016:3019362. [PMID: 27688750 DOI: 10.1155/2016/3019362] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Accepted: 08/03/2016] [Indexed: 12/19/2022] Open
Abstract
Helicobacter pylori colonizes the stomachs of greater than 50% of the world's human population making it arguably one of the most successful bacterial pathogens. Chronic H. pylori colonization results in gastritis in nearly all patients; however in a subset of people, persistent infection with H. pylori is associated with an increased risk for more severe disease outcomes including B-cell lymphoma of mucosal-associated lymphoid tissue (MALT lymphoma) and invasive adenocarcinoma. Research aimed at elucidating determinants that mediate disease progression has revealed genetic differences in both humans and H. pylori which increase the risk for developing gastric cancer. Furthermore, host diet and nutrition status have been shown to influence H. pylori-associated disease outcomes. In this review we will discuss how H. pylori is able to create a replicative niche within the hostile host environment by subverting and modifying the host-generated immune response as well as successfully competing for limited nutrients such as transition metals by deploying an arsenal of metal acquisition proteins and virulence factors. Lastly, we will discuss how micronutrient availability or alterations in the gastric microbiome may exacerbate negative disease outcomes associated with H. pylori colonization.
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11
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Abstract
Nickel is an essential transition metal for the survival of Helicobacter pylori in the acidic human stomach. The nickel-responsive transcriptional regulator HpNikR is important for maintaining healthy cytosolic nickel concentrations through the regulation of multiple genes, but its complete regulon and role in nickel homeostasis are not well understood. To investigate potential gene targets of HpNikR, ChIP sequencing was performed using H. pylori grown at neutral pH in nickel-supplemented media and this experiment identified HPG27_866 (frpB2) and HPG27_1499 (ceuE). These two genes are annotated to encode a putative iron transporter and a nickel-binding, periplasmic component of an ABC transporter, respectively. In vitro DNA-binding assays revealed that HpNikR binds both gene promoter sequences in a nickel-responsive manner with affinities on the order of ∼10(-7) M. The recognition sites of HpNikR were identified and loosely correlate with the HpNikR pseudo-consensus sequence (TATTATT-N11-AATAATA). Quantitative PCR experiments revealed that HPG27_866 and HPG27_1499 are transcriptionally repressed following growth of H. pylori G27 in nickel-supplemented media, and that this response is dependent on HpNikR. In contrast, iron supplementation results in activation of HPG27_1499, but no impact on the expression of HPG27_866 was observed. Metal analysis of the Δ866 strain revealed that HPG27_866 has an impact on nickel accumulation. These studies demonstrate that HPG27_866 and HPG27_1499 are both direct targets of HpNikR and that HPG27_866 influences nickel uptake in H. pylori.
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Affiliation(s)
- M D Jones
- Department of Chemistry, University of Toronto, 80 St. George St., Toronto, ON, M5S 3H6, Canada.
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12
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Loh JT, Gaddy JA, Algood HM, Gaudieri S, Mallal S, Cover TL. Helicobacter pylori adaptation in vivo in response to a high-salt diet. Infect Immun 2015; 83:4871-83. [PMID: 26438795 DOI: 10.1128/IAI.00918-15] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Accepted: 09/30/2015] [Indexed: 12/21/2022] Open
Abstract
Helicobacter pylori exhibits a high level of intraspecies genetic diversity. In this study, we investigated whether the diversification of H. pylori is influenced by the composition of the diet. Specifically, we investigated the effect of a high-salt diet (a known risk factor for gastric adenocarcinoma) on H. pylori diversification within a host. We analyzed H. pylori strains isolated from Mongolian gerbils fed either a high-salt diet or a regular diet for 4 months by proteomic and whole-genome sequencing methods. Compared to the input strain and output strains from animals fed a regular diet, the output strains from animals fed a high-salt diet produced higher levels of proteins involved in iron acquisition and oxidative-stress resistance. Several of these changes were attributable to a nonsynonymous mutation in fur (fur-R88H). Further experiments indicated that this mutation conferred increased resistance to high-salt conditions and oxidative stress. We propose a model in which a high-salt diet leads to high levels of gastric inflammation and associated oxidative stress in H. pylori-infected animals and that these conditions, along with the high intraluminal concentrations of sodium chloride, lead to selection of H. pylori strains that are most fit for growth in this environment.
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13
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Abstract
Helicobacter pylori is a Gram-negative spiral-shaped bacterium that colonizes over half of the world's population. Chronic H. pylori infection is associated with increased risk for numerous disease outcomes including gastritis, dysplasia, neoplasia, B-cell lymphoma of mucosal-associated lymphoid tissue (MALT lymphoma), and invasive adenocarcinoma. The complex interactions that occur between pathogen and host are dynamic and exquisitely regulated, and the relationship between H. pylori and its human host are no exception. To successfully colonize, and subsequently persist, within the human stomach H. pylori must temporally regulate numerous genes to ensure localization to the gastric lumen and coordinated expression of virulence factors to subvert the host's innate and adaptive immune response. H. pylori achieves this precise gene regulation by sensing subtle environmental changes including host-mediated alterations in nutrient availability and responding with dramatic global changes in gene expression. Recent studies revealed that the presence or absence of numerous metal ions encountered in the lumen of the stomach, or within host tissues, including nickel, iron, copper and zinc, can influence regulatory networks to alter gene expression in H. pylori. These expression changes modulate the deployment of bacterial virulence factors that can ultimately influence disease outcome. In this review we will discuss the environmental stimuli that are detected by H. pylori as well as the trans regulatory elements, specifically the transcription regulators and transcription factors, that allow for these significant transcriptional shifts.
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Affiliation(s)
- Kathryn P Haley
- Tennessee Valley Healthcare Services, Department of Veterans Affairs Nashville, TN, USA
| | - Jennifer A Gaddy
- Department of Medicine, Vanderbilt University School of Medicine Nashville, TN, USA ; Tennessee Valley Healthcare Services, Department of Veterans Affairs Nashville, TN, USA
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14
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Pelliciari S, Vannini A, Roncarati D, Danielli A. The allosteric behavior of Fur mediates oxidative stress signal transduction in Helicobacter pylori. Front Microbiol 2015; 6:840. [PMID: 26347726 PMCID: PMC4541418 DOI: 10.3389/fmicb.2015.00840] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 07/31/2015] [Indexed: 12/19/2022] Open
Abstract
The microaerophilic gastric pathogen Helicobacter pylori is exposed to oxidative stress originating from the aerobic environment, the oxidative burst of phagocytes and the formation of reactive oxygen species, catalyzed by iron excess. Accordingly, the expression of genes involved in oxidative stress defense have been repeatedly linked to the ferric uptake regulator Fur. Moreover, mutations in the Fur protein affect the resistance to metronidazole, likely due to loss-of-function in the regulation of genes involved in redox control. Although many advances in the molecular understanding of HpFur function were made, little is known about the mechanisms that enable Fur to mediate the responses to oxidative stress. Here we show that iron-inducible, apo-Fur repressed genes, such as pfr and hydA, are induced shortly after oxidative stress, while their oxidative induction is lost in a fur knockout strain. On the contrary, holo-Fur repressed genes, such as frpB1 and fecA1, vary modestly in response to oxidative stress. This indicates that the oxidative stress signal specifically targets apo-Fur repressed genes, rather than impairing indiscriminately the regulatory function of Fur. Footprinting analyses showed that the oxidative signal strongly impairs the binding affinity of Fur toward apo-operators, while the binding toward holo-operators is less affected. Further evidence is presented that a reduced state of Fur is needed to maintain apo-repression, while oxidative conditions shift the preferred binding architecture of Fur toward the holo-operator binding conformation, even in the absence of iron. Together the results demonstrate that the allosteric regulation of Fur enables transduction of oxidative stress signals in H. pylori, supporting the concept that apo-Fur repressed genes can be considered oxidation inducible Fur regulatory targets. These findings may have important implications in the study of H. pylori treatment and resistance to antibiotics.
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Affiliation(s)
- Simone Pelliciari
- Department of Pharmacy and Biotechnology (FaBiT), University of Bologna , Bologna, Italy
| | - Andrea Vannini
- Department of Pharmacy and Biotechnology (FaBiT), University of Bologna , Bologna, Italy
| | - Davide Roncarati
- Department of Pharmacy and Biotechnology (FaBiT), University of Bologna , Bologna, Italy
| | - Alberto Danielli
- Department of Pharmacy and Biotechnology (FaBiT), University of Bologna , Bologna, Italy
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15
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Abstract
BACKGROUND Helicobacter pylori, a gram negative bacterium, colonizes the stomach in a majority of the world population. The two major virulence factors of H. pylori VacA and CagA, thought to be associated with chronic inflammation and disease, have been extensively studied, but the regulation of the expression of these virulence genes in H. pylori remains poorly understood. METHODS qRT-PCR was performed to quantify gene expression in unadhered and AGS-adhered H. pylori. Δfur mutant was constructed by splicing by overlap extension PCR and allelic exchange. RESULTS Adherence of H. pylori to the gastric epithelial cell line AGS strongly induces the expression of both cagA and vacA. Induction of cagA and vacA in the AGS cell-adhered H. pylori Δfur mutant strain was consistently lower than in the adhered parent strain. However, expression of the genes was similar between the wild-type and Δfur mutant strains in the unadhered state, suggesting that Fur has a role in the upregulation of cagA and vacA expression, especially in AGS-adhered H. pylori. Consistent with these results, microscopic observations revealed that infection of AGS cells with H. pylori Δfur mutant strain produced much less damage as compared to that produced by the wild-type H. pylori strain. CONCLUSIONS These results suggested that cagA and vacA gene expression is upregulated in H. pylori, especially by host cell contact, and Fur has a role in the upregulation.
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Affiliation(s)
- Raghwan
- Infectious Diseases and Immunology Division, Indian Institute of Chemical Biology, Council of Scientific and Industrial Research, Kolkata, India
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16
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Shaik MM, Cendron L, Salamina M, Ruzzene M, Zanotti G. Helicobacter pylori periplasmic receptor CeuE (HP1561) modulates its nickel affinity via organic metallophores. Mol Microbiol 2014; 91:724-35. [PMID: 24330328 DOI: 10.1111/mmi.12487] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/08/2013] [Indexed: 11/30/2022]
Abstract
In Gram-negative bacteria, nickel uptake is guaranteed by multiple and complex systems that operate at the membrane and periplasmic level. Helicobacter pylori employs other yet uncharacterized systems to import the nickel required for the maturation of key enzymes, such as urease and hydrogenase. H. pylori CeuE protein (HP1561), previously annotated as the periplasmic component of an ATP-binding cassette (ABC)-type transporter apparatus responsible of haem/siderophores or other Fe(III)-complexes uptake, has been recently proposed to be on the contrary involved in nickel/cobalt acquisition. In this work, the crystal structure of H. pylori CeuE has been determined at 1.65 Å resolution using the single anomalous dispersion (SAD) method. It comprises two structurally similar globular domains, each consisting of a central five-stranded β-sheet surrounded by α-helices, an arrangement commonly classified as a Rossmann-like fold. Structurally, H. pylori CeuE belongs to the class III periplasmic substrate-binding protein. Both crystallographic data and fluorescence binding assays allow to exclude a role of the protein in the transport of Vitamin B12, enterobactin, haem and isolated Ni(2+) ions. On the contrary, the crystal structure and plasmon resonance studies about CeuE/Ni-(l-His)2 complex indicate that in H. pylori nickel transport is supported by CeuE protein and requires the presence of a natural nickelophore, analogously to what has been recently demonstrated for NikA from Escherichia coli.
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Affiliation(s)
- Md Munan Shaik
- Department of Biomedical Sciences, University of Padua, Viale G. Colombo 3, 35131, Padua, Italy
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17
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Pich OQ, Merrell DS. The ferric uptake regulator of Helicobacter pylori: a critical player in the battle for iron and colonization of the stomach. Future Microbiol 2013; 8:725-38. [PMID: 23701330 DOI: 10.2217/fmb.13.43] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Helicobacter pylori is arguably one of the most successful pathogens; it colonizes the stomachs of more than half of the human population. Colonization and persistence in such an inhospitable niche requires the presence of exquisite adaptive mechanisms. One of the proteins that contributes significantly to the remarkable adaptability of H. pylori is the ferric uptake regulator (Fur), which functions as a master regulator of gene expression. In addition to genes directly related to iron homeostasis, Fur controls expression of several enzymes that play a central role in metabolism and energy production. The absence of Fur leads to severe H. pylori colonization defects and, accordingly, several Fur-regulated genes have been shown to be essential for colonization. Moreover, proteins encoded by Fur-regulated genes have a strong impact on redox homeostasis in the stomach and are major determinants of inflammation. In this review, we discuss the main roles of Fur in the biology of H. pylori and highlight the importance of this regulatory protein in the infectious process.
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Affiliation(s)
- Oscar Q Pich
- Department of Microbiology & Immunology, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814, USA
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18
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McClain MS, Duncan SS, Gaddy JA, Cover TL. Control of gene expression in Helicobacter pylori using the Tet repressor. J Microbiol Methods 2013; 95:336-41. [PMID: 24113399 PMCID: PMC3856897 DOI: 10.1016/j.mimet.2013.09.019] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Revised: 09/25/2013] [Accepted: 09/30/2013] [Indexed: 01/15/2023]
Abstract
The lack of a versatile system to control gene expression in Helicobacter pylori has hampered efforts to study H. pylori physiology and pathogenesis. To overcome these limitations, we evaluated the utility of an inducible system based on the well-characterized Tet repressor (TetR) and Tet operator (tetO). As validation of this system, we introduced three copies of tetO into the promoter region upstream of the cagUT operon (encoding two virulence factors required for function of the H. pylori Cag type IV secretion system) and expressed tetR by introducing a codon-optimized gene into the chromosomal ureA locus. Introduction of the tetO copies upstream of cagUT did not disrupt promoter activity, as determined by immunoblotting for CagT. The subsequent introduction of tetR, however, did repress CagT synthesis. Production of CagT was restored when strains were cultured in the presence of the inducer, anhydrotetracycline. To demonstrate one potential application of this new tool, we analyzed the function of the Cag type IV secretion system. When the modified H. pylori strains were co-cultured with AGS cells, activity of the Cag type IV secretion system was dependent on the presence of anhydrotetracycline as evidenced by inducer-dependent induction of IL-8 secretion, CagA translocation, and appearance of type IV secretion system pili at the bacteria-host interface. These studies demonstrate the effectiveness of the tetR-tetO system to control gene expression in H. pylori and provide an improved system for studying H. pylori physiology and pathogenesis.
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Affiliation(s)
- Mark S. McClain
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Stacy S. Duncan
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Jennifer A. Gaddy
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- Veterans Affairs Tennessee Valley Healthcare System, Nashville, Tennessee, United States of America
| | - Timothy L. Cover
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- Veterans Affairs Tennessee Valley Healthcare System, Nashville, Tennessee, United States of America
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19
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Lee S, Kim MK, Ji CJ, Lee JW, Cha SS. Experimental phasing using zinc and sulfur anomalous signals measured at the zinc absorption peak. J Microbiol 2013; 51:639-43. [PMID: 24173644 DOI: 10.1007/s12275-013-3412-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Accepted: 08/27/2013] [Indexed: 10/26/2022]
Abstract
Iron is an essential transition metal required for bacterial growth and survival. Excess free iron can lead to the generation of reactive oxygen species that can cause severe damage to cellular functions. Cells have developed iron-sensing regulators to maintain iron homeostasis at the transcription level. The ferric uptake regulator (Fur) is an iron-responsive regulator that controls the expression of genes involved in iron homeostasis, bacterial virulence, stress resistance, and redox metabolism. Here, we report the expression, purification, crystallization, and phasing of the apo-form of Bacillus subtilis Fur (BsFur) in the absence of regulatory metal ions. Crystals were obtained by microbatch crystallization method at 295 K and diffraction data at a resolution of 2.6 Å was collected at the zinc peak wavelength (λ=1.2823 Å). Experimental phasing identified the positions of one zinc atom and four sulfur atoms of cysteine residues coordinating the zinc atom, indicating that the data contained a meaningful anomalous scattering originating from the ordered zinc-coordinating sulfur atoms, in spite of the small anomalous signals of sulfur atoms at the examined wavelength.
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20
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Carpenter BM, Gilbreath JJ, Pich OQ, McKelvey AM, Maynard EL, Li ZZ, Merrell DS. Identification and characterization of novel Helicobacter pylori apo-fur-regulated target genes. J Bacteriol 2013; 195:5526-39. [PMID: 24097951 DOI: 10.1128/JB.01026-13] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
In Helicobacter pylori, the ferric uptake regulator (Fur) has evolved additional regulatory functions not seen in other bacteria; it can repress and activate different groups of genes in both its iron-bound and apo forms. Because little is understood about the process of apo-Fur repression and because only two apo-Fur-repressed genes (pfr and sodB) have previously been identified, we sought to expand our understanding of this type of regulation. Utilizing published genomic studies, we selected three potential new apo-Fur-regulated gene targets: serB, hydA, and the cytochrome c553 gene. Transcriptional analyses confirmed Fur-dependent repression of these genes in the absence of iron, as well as derepression in the absence of Fur. Binding studies showed that apo-Fur directly interacted with the suspected hydA and cytochrome c553 promoters but not that of serB, which was subsequently shown to be cotranscribed with pfr; apo-Fur-dependent regulation occurred at the pfr promoter. Alignments of apo-regulated promoter regions revealed a conserved, 6-bp consensus sequence (AAATGA). DNase I footprinting showed that this sequence lies within the protected regions of the pfr and hydA promoters. Moreover, mutation of the sequence in the pfr promoter abrogated Fur binding and DNase protection. Likewise, fluorescence anisotropy studies and binding studies with mutated consensus sequences showed that the sequence was important for apo-Fur binding to the pfr promoter. Together these studies expand the known apo-Fur regulon in H. pylori and characterize the first reported apo-Fur box sequence.
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21
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Troxell B, Hassan HM. Transcriptional regulation by Ferric Uptake Regulator (Fur) in pathogenic bacteria. Front Cell Infect Microbiol 2013; 3:59. [PMID: 24106689 PMCID: PMC3788343 DOI: 10.3389/fcimb.2013.00059] [Citation(s) in RCA: 290] [Impact Index Per Article: 26.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Accepted: 09/18/2013] [Indexed: 12/16/2022] Open
Abstract
In the ancient anaerobic environment, ferrous iron (Fe2+) was one of the first metal cofactors. Oxygenation of the ancient world challenged bacteria to acquire the insoluble ferric iron (Fe3+) and later to defend against reactive oxygen species (ROS) generated by the Fenton chemistry. To acquire Fe3+, bacteria produce low-molecular weight compounds, known as siderophores, which have extremely high affinity for Fe3+. However, during infection the host restricts iron from pathogens by producing iron- and siderophore-chelating proteins, by exporting iron from intracellular pathogen-containing compartments, and by limiting absorption of dietary iron. Ferric Uptake Regulator (Fur) is a transcription factor which utilizes Fe2+ as a corepressor and represses siderophore synthesis in pathogens. Fur, directly or indirectly, controls expression of enzymes that protect against ROS damage. Thus, the challenges of iron homeostasis and defense against ROS are addressed via Fur. Although the role of Fur as a repressor is well-documented, emerging evidence demonstrates that Fur can function as an activator. Fur activation can occur through three distinct mechanisms (1) indirectly via small RNAs, (2) binding at cis regulatory elements that enhance recruitment of the RNA polymerase holoenzyme (RNAP), and (3) functioning as an antirepressor by removing or blocking DNA binding of a repressor of transcription. In addition, Fur homologs control defense against peroxide stress (PerR) and control uptake of other metals such as zinc (Zur) and manganese (Mur) in pathogenic bacteria. Fur family members are important for virulence within bacterial pathogens since mutants of fur, perR, or zur exhibit reduced virulence within numerous animal and plant models of infection. This review focuses on the breadth of Fur regulation in pathogenic bacteria.
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Affiliation(s)
- Bryan Troxell
- Department of Immunology and Microbiology, Indiana University School of Medicine Indianapolis, IN, USA
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22
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Gilbreath JJ, Pich OQ, Benoit SL, Besold AN, Cha JH, Maier RJ, Michel SLJ, Maynard EL, Merrell DS. Random and site-specific mutagenesis of the Helicobacter pylori ferric uptake regulator provides insight into Fur structure-function relationships. Mol Microbiol 2013; 89:304-23. [PMID: 23710935 DOI: 10.1111/mmi.12278] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/22/2013] [Indexed: 12/29/2022]
Abstract
The ferric uptake regulator (Fur) of Helicobacter pylori is a global regulator that is important for colonization and survival within the gastric mucosa. H. pylori Fur is unique in its ability to activate and repress gene expression in both the iron-bound (Fe-Fur) and apo forms (apo-Fur). In the current study we combined random and site-specific mutagenesis to identify amino acid residues important for both Fe-Fur and apo-Fur function. We identified 25 mutations that affected Fe-Fur repression and 23 mutations that affected apo-Fur repression, as determined by transcriptional analyses of the Fe-Fur target gene amiE, and the apo-Fur target gene, pfr. In addition, eight of these mutations also significantly affected levels of Fur in the cell. Based on regulatory phenotypes, we selected several representative mutations to characterize further. Of those selected, we purified the wild-type (HpFurWT) and three mutant Fur proteins (HpFurE5A, HpFurA92T and HpFurH134Y), which represent mutations in the N-terminal extension, the regulatory metal binding site (S2) and the structural metal binding site (S3) respectively. Purified proteins were evaluated for secondary structure by circular dichroism spectroscopy, iron-binding by atomic absorption spectrophotometry, oligomerization in manganese-substituted and apo conditions by in vitro cross-linking assays, and DNA binding to Fe-Fur and apo-Fur target sequences by fluorescence anisotropy. The results showed that the N-terminal, S2 and S3 regions play distinct roles in terms of Fur structure-function relationships. Overall, these studies provide novel information regarding the role of these residues in Fur function, and provide mechanistic insight into how H. pylori Fur regulates gene expression in both the iron-bound and apo forms of the protein.
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Affiliation(s)
- Jeremy J Gilbreath
- Department of Microbiology and Immunology, Uniformed Services University of Health Sciences, Bethesda, MD, USA
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23
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Gilbreath JJ, West AL, Pich OQ, Carpenter BM, Michel S, Merrell DS. Fur activates expression of the 2-oxoglutarate oxidoreductase genes (oorDABC) in Helicobacter pylori. J Bacteriol 2012; 194:6490-7. [PMID: 23002221 DOI: 10.1128/JB.01226-12] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Helicobacter pylori is a highly successful pathogen that colonizes the gastric mucosa of ∼50% of the world's population. Within this colonization niche, the bacteria encounter large fluctuations in nutrient availability. As such, it is critical that this organism regulate expression of key metabolic enzymes so that they are present when environmental conditions are optimal for growth. One such enzyme is the 2-oxoglutarate (α-ketoglutarate) oxidoreductase (OOR), which catalyzes the conversion of α-ketoglutarate to succinyl coenzyme A (succinyl-CoA) and CO(2). Previous studies from our group suggested that the genes that encode the OOR are activated by iron-bound Fur (Fe-Fur); microarray analysis showed that expression of oorD, oorA, and oorC was altered in a fur mutant strain of H. pylori. The goal of the present work was to more thoroughly characterize expression of the oorDABC genes in H. pylori as well as to define the role of Fe-Fur in this process. Here we show that these four genes are cotranscribed as an operon and that expression of the operon is decreased in a fur mutant strain. Transcriptional start site mapping and promoter analysis revealed the presence of a canonical extended -10 element but a poorly conserved -35 element upstream of the +1. Additionally, we identified a conserved Fur binding sequence ∼130 bp upstream of the transcriptional start site. Transcriptional analysis using promoter fusions revealed that this binding sequence was required for Fe-Fur-mediated activation. Finally, fluorescence anisotropy assays indicate that Fe-Fur specifically bound this Fur box with a relatively high affinity (dissociation constant [K(d)] = 200 nM). These findings provide novel insight into the genetic regulation of a key metabolic enzyme and add to our understanding of the diverse roles Fur plays in gene regulation in H. pylori.
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24
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Vannini A, Agriesti F, Mosca F, Roncarati D, Scarlato V, Danielli A. A convenient and robust in vivo reporter system to monitor gene expression in the human pathogen Helicobacter pylori. Appl Environ Microbiol 2012; 78:6524-33. [PMID: 22773640 DOI: 10.1128/AEM.01252-12] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Thirty years of intensive research have significantly contributed to our understanding of Helicobacter pylori biology and pathogenesis. However, the lack of convenient genetic tools, in particular the limited effectiveness of available reporter systems, has notably limited the toolbox for fundamental and applied studies. Here, we report the construction of a bioluminescent H. pylori reporter system based on the Photorhabdus luminescens luxCDABE cassette. The system is constituted of a promoterless lux acceptor strain in which promoters and sequences of interest can be conveniently introduced by double homologous recombination of a suicide transformation vector. We validate the robustness of this new lux reporter system in noninvasive in vivo monitoring of dynamic transcriptional responses of inducible as well as repressible promoters and demonstrate its suitability for the implementation of genetic screens in H. pylori.
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Pich OQ, Carpenter BM, Gilbreath JJ, Merrell DS. Detailed analysis of Helicobacter pylori Fur-regulated promoters reveals a Fur box core sequence and novel Fur-regulated genes. Mol Microbiol 2012; 84:921-41. [PMID: 22507395 DOI: 10.1111/j.1365-2958.2012.08066.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
In Helicobacter pylori, iron balance is controlled by the Ferric uptake regulator (Fur), an iron-sensing repressor protein that typically regulates expression of genes implicated in iron transport and storage. Herein, we carried out extensive analysis of Fur-regulated promoters and identified a 7-1-7 motif with dyad symmetry (5'-TAATAATnATTATTA-3'), which functions as the Fur box core sequence of H. pylori. Addition of this sequence to the promoter region of a typically non-Fur regulated gene was sufficient to impose Fur-dependent regulation in vivo. Moreover, mutation of this sequence within Fur-controlled promoters negated regulation. Analysis of the H. pylori chromosome for the occurrence of the Fur box established the existence of well-conserved Fur boxes in the promoters of numerous known Fur-regulated genes, and revealed novel putative Fur targets. Transcriptional analysis of the new candidate genes demonstrated Fur-dependent repression of HPG27_51, HPG27_52, HPG27_199, HPG27_445, HPG27_825 and HPG27_1063, as well as Fur-mediated activation of the cytotoxin associated gene A, cagA (HPG27_507). Furthermore, electrophoretic mobility shift assays confirmed specific binding of Fur to the promoters of each of these genes. Future experiments will determine whether loss of Fur regulation of any of these particular genes contributes to the defects in colonization exhibited by the H. pylori fur mutant.
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Affiliation(s)
- Oscar Q Pich
- Department of Microbiology and Immunology, Uniformed Services University of the Heath Sciences, Bethesda, MD 20814, USA
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26
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Tsugawa H, Suzuki H, Matsuzaki J, Hirata K, Hibi T. FecA1, a bacterial iron transporter, determines the survival of Helicobacter pylori in the stomach. Free Radic Biol Med 2012; 52:1003-10. [PMID: 22245091 DOI: 10.1016/j.freeradbiomed.2011.12.011] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Revised: 11/16/2011] [Accepted: 12/14/2011] [Indexed: 01/14/2023]
Abstract
Helicobacter pylori encodes a single iron-cofactored superoxide dismutase (SodB), which is regulated by the ferric uptake regulator (Fur). Ferrous ion (Fe(2+)) is necessary for the activation of SodB. The activity of SodB is an important determinant of the capability of H. pylori for long-term colonization of the stomach and of the development of metronidazole (Mtz) resistance of the bacterium. This study is conducted to characterize the Fe(2+)-supply mechanisms for the activation of SodB in H. pylori, which, as mentioned above, is associated with the host-colonization ability and Mtz resistance of H. pylori. In this study, we demonstrate that fecA1, a Fe(3+)-dicitrate transporter homolog, is an essential gene for SodB activation, but not for the biogenic activity of H. pylori. H. pylori with SodB inactivation by fecA1 deletion showed reduced resistance to H(2)O(2), reduced gastric mucosal-colonization ability in Mongolian gerbils, and also reduced resistance to Mtz. Our experiment demonstrated that FecA1 is an important determinant of the host-colonization ability and Mtz resistance of H. pylori through Fe(2+) supply to SodB, suggesting that FecA1 may be a possible target for the development of a novel bactericidal drug.
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Affiliation(s)
- Hitoshi Tsugawa
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Keio University School of Medicine, Tokyo 160-8582, Japan
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Abstract
It is well established that the ferric uptake regulatory protein (Fur) functions as a transcriptional repressor in diverse microorganisms. Recent studies demonstrated that Fur also functions as a transcriptional activator. In this study we defined Fur-mediated activation of gene transcription in the sexually transmitted disease pathogen Neisseria gonorrhoeae. Analysis of 37 genes which were previously determined to be iron induced and which contained putative Fur boxes revealed that only 30 of these genes exhibited reduced transcription in a gonococcal fur mutant strain. Fur-mediated activation was established by examining binding of Fur to the putative promoter regions of 16 Fur-activated genes with variable binding affinities observed. Only ∼50% of the newly identified Fur-regulated genes bound Fur in vitro, suggesting that additional regulatory circuits exist which may function through a Fur-mediated indirect mechanism. The gonococcal Fur-activated genes displayed variable transcription patterns in a fur mutant strain, which correlated with the position of the Fur box in each (promoter) region. These results suggest that Fur-mediated direct transcriptional activation is fulfilled by multiple mechanisms involving either competing with a repressor or recruiting RNA polymerase. Collectively, our studies have established that gonococcal Fur functions as an activator of gene transcription through both direct and indirect mechanisms.
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Abstract
The stomach is a sensitive digestive organ that is susceptible and exposed to exogenous pathogens from the diet. In response to such pathogens, the stomach induces oxidative stress, which might be related to the development of gastric organic disorders such as gastritis, gastric ulcers, and gastric cancer, as well as functional disorders such as functional dyspepsia. In particular, the bacterium Helicobacter pylori plays a major role in eliciting and confronting oxidative stress in the stomach. The present paper summarizes the pathogenesis of oxidative stress in the stomach during the development of various stomach diseases.
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Affiliation(s)
- Hidekazu Suzuki
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan
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29
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Abstract
Helicobacter pylori infections are closely associated with peptic ulcers, gastric malignancy and iron deficiency anemia. Iron is essential for almost all living organisms and the investigation of iron uptake and trafficking system is thus important to understand the pathological roles of H. pylori. Up to now, the iron trafficking system of H. pylori is not yet fully clear and merits further efforts in this regards. The available information about iron uptake and regulation has been discussed in this concise review, such as FeoB in ferrous transportation, FrpB2 in hemoglobin uptake, HugZ in heme processing, virulence factors (VacA and CagA) in transferrin utilization, Pfr and NapA in iron storage and Fur in iron regulation. The identified iron trafficking system will help us to understand the pathological roles of H. pylori in the various gastric diseases and iron deficiency anemia and stimulates further development of effective anti-bacterial drugs.
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Butcher BG, Bronstein PA, Myers CR, Stodghill PV, Bolton JJ, Markel EJ, Filiatrault MJ, Swingle B, Gaballa A, Helmann JD, Schneider DJ, Cartinhour SW. Characterization of the Fur regulon in Pseudomonas syringae pv. tomato DC3000. J Bacteriol 2011; 193:4598-611. [PMID: 21784947 DOI: 10.1128/JB.00340-11] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The plant pathogen Pseudomonas syringae pv. tomato DC3000 (DC3000) is found in a wide variety of environments and must monitor and respond to various environmental signals such as the availability of iron, an essential element for bacterial growth. An important regulator of iron homeostasis is Fur (ferric uptake regulator), and here we present the first study of the Fur regulon in DC3000. Using chromatin immunoprecipitation followed by massively parallel sequencing (ChIP-seq), 312 chromosomal regions were highly enriched by coimmunoprecipitation with a C-terminally tagged Fur protein. Integration of these data with previous microarray and global transcriptome analyses allowed us to expand the putative DC3000 Fur regulon to include genes both repressed and activated in the presence of bioavailable iron. Using nonradioactive DNase I footprinting, we confirmed Fur binding in 41 regions, including upstream of 11 iron-repressed genes and the iron-activated genes encoding two bacterioferritins (PSPTO_0653 and PSPTO_4160), a ParA protein (PSPTO_0855), and a two-component system (TCS) (PSPTO_3382 to PSPTO_3380).
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Abstract
Iron is both an essential nutrient for the growth of microorganisms, as well as a dangerous metal due to its capacity to generate reactive oxygen species (ROS) via the Fenton reaction. For these reasons, bacteria must tightly control the uptake and storage of iron in a manner that restricts the build-up of ROS. Therefore, it is not surprising to find that the control of iron homeostasis and responses to oxidative stress are coordinated. The mechanisms concerned with these processes, and the interactions involved, are the subject of this review.
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Affiliation(s)
- Pierre Cornelis
- Microbial Interactions, Department of Molecular and Cellular Interactions, VIB and Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium.
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Reyes-Caballero H, Campanello GC, Giedroc DP. Metalloregulatory proteins: metal selectivity and allosteric switching. Biophys Chem 2011; 156:103-14. [PMID: 21511390 DOI: 10.1016/j.bpc.2011.03.010] [Citation(s) in RCA: 120] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2011] [Revised: 03/29/2011] [Accepted: 03/29/2011] [Indexed: 01/13/2023]
Abstract
Prokaryotic organisms have evolved the capacity to quickly adapt to a changing and challenging microenvironment in which the availability of both biologically required and non-essential transition metal ions can vary dramatically. In all bacteria, a panel of metalloregulatory proteins controls the expression of genes encoding membrane transporters and metal trafficking proteins that collectively manage metal homeostasis and resistance. These "metal sensors" are specialized allosteric proteins, in which the direct binding of a specific or small number of "cognate" metal ion(s) drives a conformational change in the regulator that allosterically activates or inhibits operator DNA binding, or alternatively, distorts the promoter structure thereby converting a poor promoter to a strong one. In this review, we discuss our current understanding of the features that control metal specificity of the allosteric response in these systems, and the role that structure, thermodynamics and conformational dynamics play in mediating allosteric activation or inhibition of DNA binding.
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Dian C, Vitale S, Leonard GA, Bahlawane C, Fauquant C, Leduc D, Muller C, de Reuse H, Michaud-Soret I, Terradot L. The structure of the Helicobacter pylori ferric uptake regulator Fur reveals three functional metal binding sites. Mol Microbiol 2011; 79:1260-75. [PMID: 21208302 DOI: 10.1111/j.1365-2958.2010.07517.x] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Fur, the ferric uptake regulator, is a transcription factor that controls iron metabolism in bacteria. Binding of ferrous iron to Fur triggers a conformational change that activates the protein for binding to specific DNA sequences named Fur boxes. In Helicobacter pylori, HpFur is involved in acid response and is important for gastric colonization in model animals. Here we present the crystal structure of a functionally active HpFur mutant (HpFur2M; C78S-C150S) bound to zinc. Although its fold is similar to that of other Fur and Fur-like proteins, the crystal structure of HpFur reveals a unique structured N-terminal extension and an unusual C-terminal helix. The structure also shows three metal binding sites: S1 the structural ZnS₄ site previously characterized biochemically in HpFur and the two zinc sites identified in other Fur proteins. Site-directed mutagenesis and spectroscopy analyses of purified wild-type HpFur and various mutants show that the two metal binding sites common to other Fur proteins can be also metallated by cobalt. DNA protection and circular dichroism experiments demonstrate that, while these two sites influence the affinity of HpFur for DNA, only one is absolutely required for DNA binding and could be responsible for the conformational changes of Fur upon metal binding while the other is a secondary site.
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Affiliation(s)
- Cyril Dian
- Structural Biology Group, European Synchrotron Radiation Facility, BP 220 F-38043 Grenoble cedex 9, France
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Tsugawa H, Suzuki H, Satoh K, Hirata K, Matsuzaki J, Saito Y, Suematsu M, Hibi T. Two amino acids mutation of ferric uptake regulator determines Helicobacter pylori resistance to metronidazole. Antioxid Redox Signal 2011; 14:15-23. [PMID: 20518707 DOI: 10.1089/ars.2010.3146] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Metronidazole (Mtz) is a prodrug that is converted to its active form when its nitro group is reduced and superoxide radicals are generated. The superoxide radicals are directly toxic to the bacterium. On the other hand, the transcriptional regulator, ferric uptake regulator (Fur), of Helicobacter pylori is a direct suppressor of the iron-cofactored superoxide dismutase SodB, which is essential for protection against superoxide attack. Here, we demonstrate that in some Mtz-resistant strains, SodB activity is induced in a dose-dependent manner on exposure to Mtz. Further, under Mtz exposure, the generation of superoxide radicals in Mtz-resistant strains was significantly reduced as compared with that in the Mtz-susceptible strains. These Mtz-resistant strains were found to carry amino acids mutation of Fur (C78Y, P114S; mutant-type Fur). The binding affinity of the mutant-type Fur to an operator sequence on the sodB promoter (Fur-Box) was significantly reduced. Our approach demonstrated that SodB expression is derepressed by mutant-type Fur, which is associated with the development of Mtz resistance.
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Affiliation(s)
- Hitoshi Tsugawa
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Keio University School of Medicine, Tokyo, Japan
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Carpenter BM, Gancz H, Benoit SL, Evans S, Olsen CH, Michel SL, Maier RJ, Merrell DS. Mutagenesis of conserved amino acids of Helicobacter pylori fur reveals residues important for function. J Bacteriol 2010; 192:5037-52. [PMID: 20644138 DOI: 10.1128/JB.00198-10] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The ferric uptake regulator (Fur) of the medically important pathogen Helicobacter pylori is unique in that it has been shown to function as a repressor both in the presence of an Fe2+ cofactor and in its apo (non-Fe2+-bound) form. However, virtually nothing is known concerning the amino acid residues that are important for Fur functioning. Therefore, mutations in six conserved amino acid residues of H. pylori Fur were constructed and analyzed for their impact on both iron-bound and apo repression. In addition, accumulation of the mutant proteins, protein secondary structure, DNA binding ability, iron binding capacity, and the ability to form higher-order structures were also examined for each mutant protein. While none of the mutated residues completely abrogated the function of Fur, we were able to identify residues that were critical for both iron-bound and apo-Fur repression. One mutation, V64A, did not alter regulation of any target genes. However, each of the five remaining mutations showed an effect on either iron-bound or apo regulation. Of these, H96A, E110A, and E117A mutations altered iron-bound Fur regulation and were all shown to influence iron binding to different extents. Additionally, the H96A mutation was shown to alter Fur oligomerization, and the E110A mutation was shown to impact oligomerization and DNA binding. Conversely, the H134A mutant exhibited changes in apo-Fur regulation that were the result of alterations in DNA binding. Although the E90A mutant exhibited alterations in apo-Fur regulation, this mutation did not affect any of the assessed protein functions. This study is the first for H. pylori to analyze the roles of specific amino acid residues of Fur in function and continues to highlight the complexity of Fur regulation in this organism.
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Miles S, Carpenter BM, Gancz H, Merrell DS. Helicobacter pylori apo-Fur regulation appears unconserved across species. J Microbiol 2010; 48:378-86. [PMID: 20571957 DOI: 10.1007/s12275-010-0022-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2010] [Accepted: 02/08/2010] [Indexed: 11/30/2022]
Abstract
The Ferric Uptake Regulator (Fur) is a transcriptional regulator that is conserved across a broad number of bacterial species and has been shown to regulate expression of iron uptake and storage genes. Additionally, Fur has been shown to be an important colonization factor of the gastric pathogen Helicobacter pylori. In H. pylori, Fur-dependent regulation appears to be unique in that Fur is able to act as a transcriptional repressor when bound to iron as well as in its iron free (apo) form. To date, apo-regulation has not been identified in any other bacterium. To determine whether Fur from other species has the capacity for apo-regulation, we investigated the ability of Fur from Escherichia coli, Campylobacter jejuni, Desulfovibrio vulgaris Hildenborough, Pseudomonas aeruginosa, and Vibrio cholerae to complement both iron-bound and apo-Fur regulation within the context of a H. pylori fur mutant. We found that while some Fur species (E. coli, C. jejuni, and V. cholerae) complemented iron-bound regulation, apo-regulation was unable to be complemented by any of the examined species. These data suggest that despite the conservation among bacterial Fur proteins, H. pylori Fur contains unique structure/function features that make it novel in comparison to Fur from other species.
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Affiliation(s)
- Shana Miles
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814, USA
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Danielli A, Amore G, Scarlato V. Built shallow to maintain homeostasis and persistent infection: insight into the transcriptional regulatory network of the gastric human pathogen Helicobacter pylori. PLoS Pathog 2010; 6:e1000938. [PMID: 20548942 DOI: 10.1371/journal.ppat.1000938] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Transcriptional regulatory networks (TRNs) transduce environmental signals into coordinated output expression of the genome. Accordingly, they are central for the adaptation of bacteria to their living environments and in host-pathogen interactions. Few attempts have been made to describe a TRN for a human pathogen, because even in model organisms, such as Escherichia coli, the analysis is hindered by the large number of transcription factors involved. In light of the paucity of regulators, the gastric human pathogen Helicobacter pylori represents a very appealing system for understanding how bacterial TRNs are wired up to support infection in the host. Herein, we review and analyze the available molecular and "-omic" data in a coherent ensemble, including protein-DNA and protein-protein interactions relevant for transcriptional control of pathogenic responses. The analysis covers approximately 80% of the annotated H. pylori regulators, and provides to our knowledge the first in-depth description of a TRN for an important pathogen. The emerging picture indicates a shallow TRN, made of four main modules (origons) that process the physiological responses needed to colonize the gastric niche. Specific network motifs confer distinct transcriptional response dynamics to the TRN, while long regulatory cascades are absent. Rather than having a plethora of specialized regulators, the TRN of H. pylori appears to transduce separate environmental inputs by using different combinations of a small set of regulators.
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Danielli A, Scarlato V. Regulatory circuits in Helicobacter pylori : network motifs and regulators involved in metal-dependent responses. FEMS Microbiol Rev 2010; 34:738-52. [PMID: 20579104 DOI: 10.1111/j.1574-6976.2010.00233.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The ability of Helicobacter pylori, one of the most successful human bacterial pathogens, to colonize the acidic gastric niche persistently, depends on the proper homeostasis of intracellular metal ions, needed as cofactors of essential metallo-proteins involved in acid acclimation, respiration and detoxification. This fundamental task is controlled at the transcriptional level mainly by the regulators Fur and NikR, involved in iron homeostasis and nickel response, respectively. Herein, we review the molecular mechanisms that underlie the activity of these key pleiotropic regulators. In addition, we will focus on their involvement in the transcriptional regulatory network of the bacterium, pinpointing a surprising complexity of network motifs that interconnects them and their gene targets. These motifs appear to confer versatile dynamics of metal-dependent responses by extensive horizontal connections between the regulators and feedback control of metal-cofactor availability.
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Miles S, Piazuelo MB, Semino-Mora C, Washington MK, Dubois A, Peek RM Jr, Correa P, Merrell DS. Detailed in vivo analysis of the role of Helicobacter pylori Fur in colonization and disease. Infect Immun 2010; 78:3073-82. [PMID: 20421381 DOI: 10.1128/IAI.00190-10] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Helicobacter pylori persistently colonizes the harsh and dynamic environment of the stomach in over one-half of the world's population and has been identified as a causal agent in a spectrum of pathologies that range from gastritis to invasive adenocarcinoma. The ferric uptake regulator (Fur) is one of the few regulatory proteins that has been identified in H. pylori. Fur regulates genes important for acid acclimation and oxidative stress and has been shown to be important for colonization of H. pylori in both murine and Mongolian gerbil models of infection. To more thoroughly define the role of Fur in vivo, we conducted an extensive temporal analysis of the location of, competitive ability of, and resultant pathology induced by a Deltafur strain in the Mongolian gerbil model of infection and compared the results to results for its wild-type parent. We found that at the earliest time points postinfection, significantly more Deltafur bacteria than wild-type bacteria were recovered. However, this trend was reversed by day 3, when there was significantly increased recovery of the wild-type strain. The increased recovery of the Deltafur strain at 1 day postinfection reflected increased recovery from both the corpus and the antrum of the stomach. When the wild-type strain was allowed to colonize first, the Deltafur strain was unable to compete for colonization at any time postinfection. However, when the Deltafur strain was allowed to colonize first, the wild type efficiently outcompeted the Deltafur strain only at early times postinfection. Finally, we demonstrated that there was a delay in the development and severity of inflammation and pathology of the Deltafur strain in the gastric mucosa even after comparable levels of colonization occurred. Together, these data indicate that H. pylori Fur is most important at early stages of infection and illustrate the importance of the ability of H. pylori to adapt to its constantly fluctuating environment when it is establishing infection, inflammation, and disease.
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Oriente F, Scarlato V, Delany I. Expression of factor H binding protein of meningococcus responds to oxygen limitation through a dedicated FNR-regulated promoter. J Bacteriol 2010; 192:691-701. [PMID: 19948796 DOI: 10.1128/JB.01308-09] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Factor H binding protein (fHBP) is a surface-exposed lipoprotein in Neisseria meningitidis, which is a component of several investigational vaccines against serogroup B meningococcus (MenB) currently in development. fHBP enables the bacterium to evade complement-mediated killing by binding factor H, a key downregulator of the complement alternative pathway, and, in addition, fHBP is important for meningococcal survival in the presence of the antimicrobial peptide LL-37. In this study, we investigate the molecular mechanisms involved in transcription and regulation of the fHBP-encoding gene, fhbp. We show that the fHBP protein is expressed from two independent transcripts: one bicistronic transcript that includes the upstream gene and a second shorter monocistronic transcript from its own dedicated promoter, P(fhbp). Transcription from the promoter P(fhbp) responds to oxygen limitation in an FNR-dependent manner, and, accordingly, the FNR protein binds to a P(fhbp) probe in vitro. Furthermore, expression in meningococci of a constitutively active FNR mutant results in the overexpression of the fHBP protein. Finally, the analysis of fHBP regulation was extended to a panel of strains expressing different fHBP allelic variants at different levels, and we demonstrate that FNR is involved in the regulation of this antigen in all but one of the strains tested. Our data suggest that oxygen limitation may play an important role in inducing the expression of fHBP from a dedicated FNR-regulated promoter. This implies a role for this protein in microenvironments lacking oxygen, for instance in the submucosa or intracellularly, in addition to its demonstrated role in serum resistance in the blood.
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Vitale S, Fauquant C, Lascoux D, Schauer K, Saint-Pierre C, Michaud-Soret I. A ZnS4 Structural Zinc Site in the Helicobacter pylori Ferric Uptake Regulator. Biochemistry 2009; 48:5582-91. [DOI: 10.1021/bi9004396] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Sylvia Vitale
- CNRS UMR 5249 Laboratoire de Chimie et Biologie des Métaux, Commissariat à l’Energie Atomique (CEA), Direction des Sciences du Vivant (DSV), l’Institut de Recherches en Technologies et Sciences pour le Vivant (iRTSV), and Université Joseph Fourier, 17 rue des Martyrs, F-38054 Grenoble Cedex 9, France
| | - Caroline Fauquant
- CNRS UMR 5249 Laboratoire de Chimie et Biologie des Métaux, Commissariat à l’Energie Atomique (CEA), Direction des Sciences du Vivant (DSV), l’Institut de Recherches en Technologies et Sciences pour le Vivant (iRTSV), and Université Joseph Fourier, 17 rue des Martyrs, F-38054 Grenoble Cedex 9, France
| | - David Lascoux
- Laboratoire de Spectrométrie de Masse des Protéines, Institut de Biologie Structurale, Jean-Pierre Ebel (UMR 5075 CNRS/CEA/UJF), F-38027 Grenoble Cedex 1, France
| | - Kristine Schauer
- Unité Pathogenèse de Helicobacter, Institut Pasteur, 28 rue du Docteur Roux, 75724 Paris Cedex 15, France
| | - Christine Saint-Pierre
- Laboratoire des Lésions des Acides Nucléiques, DSM/INAC/Service de Chimie Inorganique et Biologique, UMR E-3 CEA/UJF CNRS FRE 3200, 17 rue des Martyrs, Grenoble F-38054 Cedex 9, France
| | - Isabelle Michaud-Soret
- CNRS UMR 5249 Laboratoire de Chimie et Biologie des Métaux, Commissariat à l’Energie Atomique (CEA), Direction des Sciences du Vivant (DSV), l’Institut de Recherches en Technologies et Sciences pour le Vivant (iRTSV), and Université Joseph Fourier, 17 rue des Martyrs, F-38054 Grenoble Cedex 9, France
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Carpenter BM, Gancz H, Gonzalez-Nieves RP, West AL, Whitmire JM, Michel SLJ, Merrell DS. A single nucleotide change affects fur-dependent regulation of sodB in H. pylori. PLoS One 2009; 4:e5369. [PMID: 19399190 PMCID: PMC2671405 DOI: 10.1371/journal.pone.0005369] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2008] [Accepted: 03/27/2009] [Indexed: 11/18/2022] Open
Abstract
Helicobacter pylori is a significant human pathogen that has adapted to survive the many stresses found within the gastric environment. Superoxide Dismutase (SodB) is an important factor that helps H. pylori combat oxidative stress. sodB was previously shown to be repressed by the Ferric Uptake Regulator (Fur) in the absence of iron (apo-Fur regulation) [1]. Herein, we show that apo regulation is not fully conserved among all strains of H. pylori. apo-Fur dependent changes in sodB expression are not observed under iron deplete conditions in H. pylori strains G27, HPAG1, or J99. However, Fur regulation of pfr and amiE occurs as expected. Comparative analysis of the Fur coding sequence between G27 and 26695 revealed a single amino acid difference, which was not responsible for the altered sodB regulation. Comparison of the sodB promoters from G27 and 26695 also revealed a single nucleotide difference within the predicted Fur binding site. Alteration of this nucleotide in G27 to that of 26695 restored apo-Fur dependent sodB regulation, indicating that a single base difference is at least partially responsible for the difference in sodB regulation observed among these H. pylori strains. Fur binding studies revealed that alteration of this single nucleotide in G27 increased the affinity of Fur for the sodB promoter. Additionally, the single base change in G27 enabled the sodB promoter to bind to apo-Fur with affinities similar to the 26695 sodB promoter. Taken together these data indicate that this nucleotide residue is important for direct apo-Fur binding to the sodB promoter.
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Affiliation(s)
- Beth M. Carpenter
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States of America
| | - Hanan Gancz
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States of America
| | - Reyda P. Gonzalez-Nieves
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States of America
| | - Abby L. West
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland, United States of America
| | - Jeannette M. Whitmire
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States of America
| | - Sarah L. J. Michel
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland, United States of America
| | - D. Scott Merrell
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States of America
- * E-mail:
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Carpenter BM, Whitmire JM, Merrell DS. This is not your mother's repressor: the complex role of fur in pathogenesis. Infect Immun 2009; 77:2590-601. [PMID: 19364842 DOI: 10.1128/IAI.00116-09] [Citation(s) in RCA: 166] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
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Danielli A, Romagnoli S, Roncarati D, Costantino L, Delany I, Scarlato V. Growth phase and metal-dependent transcriptional regulation of the fecA genes in Helicobacter pylori. J Bacteriol 2009; 191:3717-25. [PMID: 19346302 DOI: 10.1128/JB.01741-08] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Balancing metal uptake is essential for maintaining a proper intracellular metal concentration. Here, we report the transcriptional control exerted by the two metal-responsive regulators of Helicobacter pylori, Fur (iron-dependent ferric uptake regulator) and NikR (nickel-responsive regulator), on the three copies of the fecA genes present in this species. By monitoring the patterns of transcription throughout growth and in response to nickel, iron, and a metal chelator, we found that the expression of the three fecA genes is temporally regulated, responds to metals in different ways, and is selectively controlled by either one of the two regulators. fecA1 is expressed at a constant level throughout growth, and its expression is iron sensitive; the expression of fecA2 is mainly off, with minor expression coming up in late exponential phase. In contrast, the expression of fecA3 is maximal in early exponential phase, gradually decreases with time, and is repressed by nickel. The direct roles of Fur and NikR were studied both in vitro, by mapping the binding sites of each regulator on the promoter regions via DNase I footprinting analysis, and in vivo, by using primer extension analyses of the fecA transcripts in fur and nikR deletion strains. Overall, the results show that the expression of each fecA gene is finely tuned in response to metal availability, as well as during the bacterial growth phase, suggesting specific and dedicated functions for the three distinct FecA homologues.
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Abstract
Helicobacter species are among the most successful colonizers of the mammalian gastrointestinal and hepatobiliary tract. Colonization is usually lifelong, indicating that Helicobacter species have evolved intricate mechanisms of dealing with stresses encountered during colonization of host tissues, like restriction of essential metal ions. The recent availability of genome sequences of the human gastric pathogen Helicobacter pylori, the murine enterohepatic pathogen Helicobacter hepaticus and the unannotated genome sequence of the ferret gastric pathogen Helicobacter mustelae has allowed for comparative genome analyses. In this review we present such analyses for metal transporters, metal-storage and metal-responsive regulators in these three Helicobacter species, and discuss possible contributions of the differences in metal metabolism in adaptation to the gastric or enterohepatic niches occupied by Helicobacter species.
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Affiliation(s)
- Clara Belzer
- Department of Gastroenterology and Hepatology, Erasmus MC-University Medical Center, Room L-455, ’s Gravendijkwal 230, 3015CE Rotterdam, The Netherlands
| | - Jeroen Stoof
- Department of Gastroenterology and Hepatology, Erasmus MC-University Medical Center, Room L-455, ’s Gravendijkwal 230, 3015CE Rotterdam, The Netherlands
| | - Arnoud H. M. van Vliet
- Department of Gastroenterology and Hepatology, Erasmus MC-University Medical Center, Room L-455, ’s Gravendijkwal 230, 3015CE Rotterdam, The Netherlands
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Abstract
Iron is essential for the survival of almost all organisms, although excess iron can result in the generation of free radicals which are toxic to cells. To avoid the toxic effects of free radicals, the concentration of intracellular iron is generally regulated by the ferric uptake regulator Fur in bacteria. The 150 aa fur ORF from Listeria monocytogenes was cloned into pRSETa, and the His-tagged fusion protein was purified by nickel affinity column chromatography. DNA binding activity of this protein was studied by an electrophoretic mobility shift assay using the end-labelled promoters P(fhuDC) and P(fur). The results showed a decrease in migration for both promoter DNAs in the presence of the Fur protein, and the change in migration was competitively inhibited with an excess of the same unlabelled promoters. No shift in migration was observed when a similar assay was performed using non-specific end-labelled DNA. The assay showed that binding of Fur to P(fur) or P(fhuDC) was independent of iron or manganese ions, and was not inhibited in the presence of 2 mM EDTA. Inductively coupled plasma MS of the Fur protein showed no iron or manganese, but 0.48 mole zinc per mole protein was detected. A DNase I protection assay revealed that Fur specifically bound to and protected a 19 bp consensus Fur box sequence located in the promoters of fur and fhuDC. There was no requirement for iron or manganese in this assay also. However, Northern blot analysis showed an increase in fur transcription under iron-restricted compared to high-level conditions. Thus, the study suggests that under in vitro conditions, the affinity of the Fur protein for the 19 bp Fur box sequence does not require iron, but iron availability regulates fur transcription in vivo. Thus, the regulation by Fur in this intracellular pathogen may be dependent on either the structure of the DNA binding domain or other intracellular factors yet to be identified.
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Affiliation(s)
- Nagender Ledala
- Microbiology Group, Department of Biological Sciences, Illinois State University, Normal, IL 61790-4120, USA
| | - Stacy L Pearson
- Microbiology Group, Department of Biological Sciences, Illinois State University, Normal, IL 61790-4120, USA
| | - Brian J Wilkinson
- Microbiology Group, Department of Biological Sciences, Illinois State University, Normal, IL 61790-4120, USA
| | - R K Jayaswal
- Microbiology Group, Department of Biological Sciences, Illinois State University, Normal, IL 61790-4120, USA
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Lee HJ, Bang SH, Lee KH, Park SJ. Positive regulation of fur gene expression via direct interaction of fur in a pathogenic bacterium, Vibrio vulnificus. J Bacteriol 2007; 189:2629-36. [PMID: 17237166 PMCID: PMC1855807 DOI: 10.1128/jb.01791-06] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
In pathogenic bacteria, the ability to acquire iron, which is mainly regulated by the ferric uptake regulator (Fur), is essential to maintain growth as well as its virulence. In Vibrio vulnificus, a human pathogen causing gastroenteritis and septicemia, fur gene expression is positively regulated by Fur when the iron concentration is limited (H.-J. Lee et al., J. Bacteriol. 185:5891-5896, 2003). Footprinting analysis revealed that an upstream region of the fur gene was protected by the Fur protein from DNase I under iron-depleted conditions. The protected region, from -142 to -106 relative to the transcription start site of the fur gene, contains distinct AT-rich repeats. Mutagenesis of this repeated sequence resulted in abolishment of binding by Fur. To confirm the role of this cis-acting element in Fur-mediated control of its own gene in vivo, fur expression was monitored in V. vulnificus strains using a transcriptional fusion containing the mutagenized Fur-binding site (fur(mt)::luxAB). Expression of fur(mt)::luxAB showed that it was not regulated by Fur and was not influenced by iron concentration. Therefore, this study demonstrates that V. vulnificus Fur acts as a positive regulator under iron-limited conditions by direct interaction with the fur upstream region.
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Affiliation(s)
- Hyun-Jung Lee
- Department of Parasitology, Yonsei University School of Medicine, 134 Shinchon-dong, Seodaemun-gu, Seoul 152-750, Republic of Korea
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Alamuri P, Mehta N, Burk A, Maier RJ. Regulation of the Helicobacter pylori Fe-S cluster synthesis protein NifS by iron, oxidative stress conditions, and fur. J Bacteriol 2006; 188:5325-30. [PMID: 16816209 PMCID: PMC1539971 DOI: 10.1128/jb.00104-06] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Transcription of both chromosomal and extrachromosomally introduced nifS was regulated (up-expressed) by oxygen or by supplemental iron conditions. This up-expression was not observed in a fur mutant strain background or when an iron chelator was added. Iron-bound Fur (but not apo-Fur) recognized the nifS promoter, and Fur bound significantly farther upstream (-155 bp to -190 bp and -210 to -240 bp) in the promoter than documented Helicobacter pylori Fur binding regions. This binding was stronger than Fur recognition of the flgE or napA promoter and includes a Fur recognition sequence common to the H. pylori pfr and sodB upstream areas. Studies of Fur-regulated genes in H. pylori have indicated that apo-Fur acts as a repressor, but our results demonstrate that iron-bound Fur activates (nifS) transcription.
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Affiliation(s)
- Praveen Alamuri
- Department of Microbiology, 527 Biological Sciences Bldg., The University of Georgia, Athens, GA 30602, USA
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Danielli A, Roncarati D, Delany I, Chiarini V, Rappuoli R, Scarlato V. In vivo dissection of the Helicobacter pylori Fur regulatory circuit by genome-wide location analysis. J Bacteriol 2006; 188:4654-62. [PMID: 16788174 PMCID: PMC1483005 DOI: 10.1128/jb.00120-06] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Iron homeostasis is particularly important in pathogenic bacteria, which need to compete with the host for this essential cofactor. In Helicobacter pylori, a causative agent of several gastric pathologies, iron uptake and storage genes are regulated at the transcriptional level by the ferric uptake regulator Fur. The regulatory circuit of Fur has recently come under focus because of an intimate interlink with a broader regulatory network governing metal homeostasis, acidic response, and virulence. To dissect the Fur regulatory circuit and identify in vivo targets of regulation, we developed a genome-wide location analysis protocol which allowed the identification of 200 genomic loci bound by Fur as well as the investigation of the binding efficiency of the protein to these loci in response to iron. Comparative analysis with transcriptomes of wild-type and fur deletion mutant strains allowed the distinction between targets associated with Fur regulation and genes indirectly influenced by the fur mutation. The Fur regulon includes 59 genes, 25 of which appear to be positively regulated. A case study conducted by primer extension analysis of two oppositely regulated genes, hpn2 and flaB, suggests that negative regulation as well as positive regulation occurs at the transcriptional level. Furthermore, the results revealed the existence of 13 Fur targeted loci within polycistronic operons, which were associated with transcript deregulation in the fur mutant strain. This study provides a systematic insight of Fur regulation at the genome-wide level in H. pylori and points to regulatory functions extending beyond the classical Fur repression paradigm.
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Affiliation(s)
- Alberto Danielli
- Department of Biology, University of Bologna, Via Selmi 3, 40126 Bologna, Italy
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Abstract
Very recently, an iron-rich protein, DpsA, was isolated from the extreme halophilic euryarchaeon Halobacterium salinarum JW5 and characterized. The amino acid sequence of DpsA is related to Dps proteins which belong structurally to the ferritin superfamily but differ from ferritins in their function and regulation. Employing Northern and Western blot analysis, the expression of DpsA in H. salinarum was examined throughout all growth phases and under a variety of growth conditions (iron deficiency, iron supplied growth, oxidative stress). DpsA shows increasing expression of dpsA mRNA in iron-rich media and under conditions of oxidative stress (H(2)O(2)), whereas under iron-deficient conditions mRNA-levels decrease. This is in contrast to Dps-type proteins the transcription of which is induced under conditions of iron starvation. Northern blot experiments show that the expression pattern of halobacterial DpsA is the same as that found in the few bacterial non-heme ferritin the expression pattern of which has been analyzed so far. Based on Western-blot analysis post-transcriptional regulation, typical of mammalian ferritins, can be excluded. This protein exhibits features of a non-heme type bacterial ferritin although it shares only little sequence similarity with Ftn from E. coli.
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