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Cirakli E, Basu A. A method for assaying DNA flexibility. Methods 2023; 219:68-72. [PMID: 37769928 DOI: 10.1016/j.ymeth.2023.09.007] [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] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2023] [Revised: 09/05/2023] [Accepted: 09/21/2023] [Indexed: 10/03/2023] Open
Abstract
The transcription, replication, packaging, and repair of genetic information ubiquitously involves DNA:protein interactions and other biological processes that require local mechanical distortions of DNA. The energetics of such DNA-deforming processes are thus dependent on the local mechanical properties of DNA such as bendability or torsional rigidity. Such properties, in turn, depend on sequence, making it possible for sequence to regulate diverse biological processes by controlling the local mechanical properties of DNA. A deeper understanding of how such a "mechanical code" can encode broad regulatory information has historically been hampered by the absence of technology to measure in high throughput how local DNA mechanics varies with sequence along large regions of the genome. This was overcome in a recently developed technique called loop-seq. Here we describe a variant of the loop-seq protocol, that permits making rapid flexibility measurements in low-throughput, without the need for next-generation sequencing. We use our method to validate a previous prediction about how the binding site for the bacterial transcription factor Integration Host Factor (IHF) might serve as a rigid roadblock, preventing efficient enhancer-promoter contacts in IHF site containing promoters in E. coli, which can be relieved by IHF binding.
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Affiliation(s)
- Eliz Cirakli
- Department of Chemistry, Durham University, Durham, UK; Department of Biosciences, Durham University, Durham, UK
| | - Aakash Basu
- Department of Biosciences, Durham University, Durham, UK.
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2
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Fosado YAG, Howard J, Weir S, Noy A, Leake MC, Michieletto D. Fluidification of Entanglements by a DNA Bending Protein. Phys Rev Lett 2023; 130:058203. [PMID: 36800460 DOI: 10.1103/physrevlett.130.058203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2022] [Accepted: 01/04/2023] [Indexed: 06/18/2023]
Abstract
In spite of the nanoscale and single-molecule insights into nucleoid associated proteins (NAPs), their role in modulating the mesoscale viscoelasticity of entangled DNA has been overlooked so far. By combining microrheology and molecular dynamics simulation, we find that the abundant NAP "integration host factor" (IHF) lowers the viscosity of entangled λDNA 20-fold at physiological concentrations and stoichiometries. Our results suggest that IHF may play a previously unappreciated role in resolving DNA entanglements and in turn may be acting as a "genomic fluidizer" for bacterial genomes.
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Affiliation(s)
- Yair A G Fosado
- School of Physics and Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
| | - Jamieson Howard
- School of Physics, Engineering and Technology, University of York, York, YO10 5DD, United Kingdom
| | - Simon Weir
- School of Physics and Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
| | - Agnes Noy
- School of Physics, Engineering and Technology, University of York, York, YO10 5DD, United Kingdom
| | - Mark C Leake
- School of Physics, Engineering and Technology, University of York, York, YO10 5DD, United Kingdom
- Department of Biology, University of York, York, YO10 5DD, United Kingdom
| | - Davide Michieletto
- School of Physics and Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
- MRC Human Genetics Unit, Institute of Genetics and Cancer, University of Edinburgh, Edinburgh EH4 2XU, United Kingdom
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3
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Chen S, Hu M, Hu A, Xue Y, Wang S, Liu F, Li C, Zhou X, Zhou J. The integration host factor regulates multiple virulence pathways in bacterial pathogen Dickeya zeae MS2. Mol Plant Pathol 2022; 23:1487-1507. [PMID: 35819797 PMCID: PMC9452768 DOI: 10.1111/mpp.13244] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Revised: 06/12/2022] [Accepted: 06/15/2022] [Indexed: 06/15/2023]
Abstract
Dickeya zeae is an aggressive bacterial phytopathogen that infects a wide range of host plants. It has been reported that integration host factor (IHF), a nucleoid-associated protein consisting of IHFα and IHFβ subunits, regulates gene expression by influencing nucleoid structure and DNA bending. To define the role of IHF in the pathogenesis of D. zeae MS2, we deleted either and both of the IHF subunit encoding genes ihfA and ihfB, which significantly reduced the production of cell wall-degrading enzymes (CWDEs), an unknown novel phytotoxin and the virulence factor-modulating (VFM) quorum-sensing (QS) signal, cell motility, biofilm formation, and thereafter the infection ability towards both potato slices and banana seedlings. To characterize the regulatory pathways of IHF protein associated with virulence, IHF binding sites (consensus sequence 5'-WATCAANNNNTTR-3') were predicted and 272 binding sites were found throughout the genome. The expression of 110 tested genes was affected by IHF. Electrophoretic mobility shift assay (EMSA) showed direct interaction of IhfA protein with the promoters of vfmE, speA, pipR, fis, slyA, prtD, hrpL, hecB, hcp, indA, hdaA, flhD, pilT, gcpJ, arcA, arcB, and lysR. This study clarified the contribution of IHF in the pathogenic process of D. zeae by controlling the production of VFM and putrescine QS signals, phytotoxin, and indigoidine, the luxR-solo system, Fis, SlyA, and FlhD transcriptional regulators, and secretion systems from type I to type VI. Characterization of the regulatory networks of IHF in D. zeae provides a target for prevention and control of plant soft rot disease.
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Affiliation(s)
- Shanshan Chen
- Guangdong Province Key Laboratory of Microbial Signals and Disease ControlIntegrative Microbiology Research Center, South China Agricultural UniversityGuangzhouChina
| | - Ming Hu
- Guangdong Province Key Laboratory of Microbial Signals and Disease ControlIntegrative Microbiology Research Center, South China Agricultural UniversityGuangzhouChina
| | - Anqun Hu
- Guangdong Province Key Laboratory of Microbial Signals and Disease ControlIntegrative Microbiology Research Center, South China Agricultural UniversityGuangzhouChina
| | - Yang Xue
- Guangdong Province Key Laboratory of Microbial Signals and Disease ControlIntegrative Microbiology Research Center, South China Agricultural UniversityGuangzhouChina
| | - Si Wang
- Guangdong Province Key Laboratory of Microbial Signals and Disease ControlIntegrative Microbiology Research Center, South China Agricultural UniversityGuangzhouChina
| | - Fan Liu
- Guangdong Province Key Laboratory of Microbial Signals and Disease ControlIntegrative Microbiology Research Center, South China Agricultural UniversityGuangzhouChina
| | - Chuhao Li
- Guangdong Province Key Laboratory of Microbial Signals and Disease ControlIntegrative Microbiology Research Center, South China Agricultural UniversityGuangzhouChina
| | - Xiaofan Zhou
- Guangdong Province Key Laboratory of Microbial Signals and Disease ControlIntegrative Microbiology Research Center, South China Agricultural UniversityGuangzhouChina
| | - Jianuan Zhou
- Guangdong Province Key Laboratory of Microbial Signals and Disease ControlIntegrative Microbiology Research Center, South China Agricultural UniversityGuangzhouChina
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Kruse T, Benz C, Garvanska DH, Lindqvist R, Mihalic F, Coscia F, Inturi R, Sayadi A, Simonetti L, Nilsson E, Ali M, Kliche J, Moliner Morro A, Mund A, Andersson E, McInerney G, Mann M, Jemth P, Davey NE, Överby AK, Nilsson J, Ivarsson Y. Large scale discovery of coronavirus-host factor protein interaction motifs reveals SARS-CoV-2 specific mechanisms and vulnerabilities. Nat Commun 2021; 12:6761. [PMID: 34799561 PMCID: PMC8605023 DOI: 10.1038/s41467-021-26498-z] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Accepted: 10/06/2021] [Indexed: 12/13/2022] Open
Abstract
Viral proteins make extensive use of short peptide interaction motifs to hijack cellular host factors. However, most current large-scale methods do not identify this important class of protein-protein interactions. Uncovering peptide mediated interactions provides both a molecular understanding of viral interactions with their host and the foundation for developing novel antiviral reagents. Here we describe a viral peptide discovery approach covering 23 coronavirus strains that provides high resolution information on direct virus-host interactions. We identify 269 peptide-based interactions for 18 coronaviruses including a specific interaction between the human G3BP1/2 proteins and an ΦxFG peptide motif in the SARS-CoV-2 nucleocapsid (N) protein. This interaction supports viral replication and through its ΦxFG motif N rewires the G3BP1/2 interactome to disrupt stress granules. A peptide-based inhibitor disrupting the G3BP1/2-N interaction dampened SARS-CoV-2 infection showing that our results can be directly translated into novel specific antiviral reagents.
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Affiliation(s)
- Thomas Kruse
- The Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Faculty of Health and Medical Sciences, Blegdamsvej 3B, 2200, Copenhagen, Denmark
| | - Caroline Benz
- Department of Chemistry - BMC, Uppsala University, Box 576, Husargatan 3, 751 23, Uppsala, Sweden
| | - Dimitriya H Garvanska
- The Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Faculty of Health and Medical Sciences, Blegdamsvej 3B, 2200, Copenhagen, Denmark
| | - Richard Lindqvist
- Department of Clinical Microbiology, Umeå University, 90185, Umeå, Sweden
- Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, 90186, Umeå, Sweden
| | - Filip Mihalic
- Department of Medical Biochemistry and Microbiology, Uppsala University, BMC, Box 582, Husargatan 3, 751 23, Uppsala, Sweden
| | - Fabian Coscia
- The Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Faculty of Health and Medical Sciences, Blegdamsvej 3B, 2200, Copenhagen, Denmark
- Spatial Proteomics Group, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, 13125, Berlin, Germany
| | - Raviteja Inturi
- Department of Medical Biochemistry and Microbiology, Uppsala University, BMC, Box 582, Husargatan 3, 751 23, Uppsala, Sweden
| | - Ahmed Sayadi
- Department of Chemistry - BMC, Uppsala University, Box 576, Husargatan 3, 751 23, Uppsala, Sweden
| | - Leandro Simonetti
- Department of Chemistry - BMC, Uppsala University, Box 576, Husargatan 3, 751 23, Uppsala, Sweden
| | - Emma Nilsson
- Department of Clinical Microbiology, Umeå University, 90185, Umeå, Sweden
- Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, 90186, Umeå, Sweden
| | - Muhammad Ali
- Department of Chemistry - BMC, Uppsala University, Box 576, Husargatan 3, 751 23, Uppsala, Sweden
| | - Johanna Kliche
- Department of Chemistry - BMC, Uppsala University, Box 576, Husargatan 3, 751 23, Uppsala, Sweden
| | - Ainhoa Moliner Morro
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Andreas Mund
- The Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Faculty of Health and Medical Sciences, Blegdamsvej 3B, 2200, Copenhagen, Denmark
| | - Eva Andersson
- Department of Medical Biochemistry and Microbiology, Uppsala University, BMC, Box 582, Husargatan 3, 751 23, Uppsala, Sweden
| | - Gerald McInerney
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Matthias Mann
- The Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Faculty of Health and Medical Sciences, Blegdamsvej 3B, 2200, Copenhagen, Denmark
| | - Per Jemth
- Department of Medical Biochemistry and Microbiology, Uppsala University, BMC, Box 582, Husargatan 3, 751 23, Uppsala, Sweden
| | - Norman E Davey
- Division of Cancer Biology, The Institute of Cancer Research, 237 Fulham Road, London, SW3 6JB, UK
| | - Anna K Överby
- Department of Clinical Microbiology, Umeå University, 90185, Umeå, Sweden.
- Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, 90186, Umeå, Sweden.
| | - Jakob Nilsson
- The Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Faculty of Health and Medical Sciences, Blegdamsvej 3B, 2200, Copenhagen, Denmark.
| | - Ylva Ivarsson
- Department of Chemistry - BMC, Uppsala University, Box 576, Husargatan 3, 751 23, Uppsala, Sweden.
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Devaraj A, González JF, Eichar B, Thilliez G, Kingsley RA, Baker S, Allard MW, Bakaletz LO, Gunn JS, Goodman SD. Enhanced biofilm and extracellular matrix production by chronic carriage versus acute isolates of Salmonella Typhi. PLoS Pathog 2021; 17:e1009209. [PMID: 33465146 PMCID: PMC7815147 DOI: 10.1371/journal.ppat.1009209] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [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: 10/13/2020] [Accepted: 12/02/2020] [Indexed: 01/01/2023] Open
Abstract
Salmonella Typhi is the primary causative agent of typhoid fever; an acute systemic infection that leads to chronic carriage in 3–5% of individuals. Chronic carriers are asymptomatic, difficult to treat and serve as reservoirs for typhoid outbreaks. Understanding the factors that contribute to chronic carriage is key to development of novel therapies to effectively resolve typhoid fever. Herein, although we observed no distinct clustering of chronic carriage isolates via phylogenetic analysis, we demonstrated that chronic isolates were phenotypically distinct from acute infection isolates. Chronic carriage isolates formed significantly thicker biofilms with greater biomass that correlated with significantly higher relative levels of extracellular DNA (eDNA) and DNABII proteins than biofilms formed by acute infection isolates. Importantly, extracellular DNABII proteins include integration host factor (IHF) and histone-like protein (HU) that are critical to the structural integrity of bacterial biofilms. In this study, we demonstrated that the biofilm formed by a chronic carriage isolate in vitro, was susceptible to disruption by a specific antibody against DNABII proteins, a successful first step in the development of a therapeutic to resolve chronic carriage. Salmonella Typhi, a human restricted pathogen is the primary etiologic agent of typhoid fever, an acute systemic infection that has a global incidence of 21 million cases annually. Although the acute infection is resolved by antibiotics, 3–5% of individuals develop chronic carriage that is difficult to resolve with antibiotics. A majority of these indivuals serve as reservoirs for further spread of the disease. Understanding the differences between acute and chronic carrier strains is key to design novel targeted approaches to undermine carriage. Here, we demonstrated that chronic carrier strains although not genotypically distinct from acute strains, formed thicker biofilms with greater relative levels of extracellular eDNA and DNABII proteins than those formed by acute infection isolates. We also demonstrated that an antibody against DNABII proteins significantly disrupted biofilms formed by a chronic carrier strain and therefore supported development of therapeutic use of this antibody to attenuate chronic carriage.
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Affiliation(s)
- Aishwarya Devaraj
- Center for Microbial Pathogenesis, Research Institute at Nationwide Children's Hospital, Columbus, Ohio, United States of America
| | - Juan F. González
- Center for Microbial Pathogenesis, Research Institute at Nationwide Children's Hospital, Columbus, Ohio, United States of America
- Department of Microbial Infection and Immunity, The Ohio State University, Columbus, Ohio, United States of America
- Department of Pediatrics, College of Medicine, The Ohio State University, Columbus, Ohio, United States of America
| | - Bradley Eichar
- Center for Microbial Pathogenesis, Research Institute at Nationwide Children's Hospital, Columbus, Ohio, United States of America
- Department of Microbial Infection and Immunity, The Ohio State University, Columbus, Ohio, United States of America
| | | | - Robert A. Kingsley
- Quadram Institute Bioscience, Norwich, United Kingdom
- University of East Anglia, Norwich, United Kingdom
| | - Stephen Baker
- Cambridge Institute of Therapeutic Immunology and Infectious Disease, University of Cambridge School of Clinical Medicine, Cambridge Biomedical Campus, Cambridge, United Kingdom
- Department of Medicine, University of Cambridge School of Clinical Medicine, Cambridge Biomedical Campus, Cambridge, United Kingdom
| | - Marc W. Allard
- Food and Drug Administration-FDA, College Park, Maryland, United States of America
| | - Lauren O. Bakaletz
- Center for Microbial Pathogenesis, Research Institute at Nationwide Children's Hospital, Columbus, Ohio, United States of America
- Department of Pediatrics, College of Medicine, The Ohio State University, Columbus, Ohio, United States of America
- Infectious Diseases Institute, The Ohio State University, Columbus, Ohio, United States of America
| | - John S. Gunn
- Center for Microbial Pathogenesis, Research Institute at Nationwide Children's Hospital, Columbus, Ohio, United States of America
- Department of Microbial Infection and Immunity, The Ohio State University, Columbus, Ohio, United States of America
- Department of Pediatrics, College of Medicine, The Ohio State University, Columbus, Ohio, United States of America
- Infectious Diseases Institute, The Ohio State University, Columbus, Ohio, United States of America
- Oral and GI Microbiology Research Affinity Group, Nationwide Children’s Hospital, Columbus, Ohio, United States of America
- * E-mail: (JSG); (SDG)
| | - Steven D. Goodman
- Center for Microbial Pathogenesis, Research Institute at Nationwide Children's Hospital, Columbus, Ohio, United States of America
- Department of Pediatrics, College of Medicine, The Ohio State University, Columbus, Ohio, United States of America
- Infectious Diseases Institute, The Ohio State University, Columbus, Ohio, United States of America
- Oral and GI Microbiology Research Affinity Group, Nationwide Children’s Hospital, Columbus, Ohio, United States of America
- * E-mail: (JSG); (SDG)
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Purkait D, Bandyopadhyay D, Mishra PP. Vital insights into prokaryotic genome compaction by nucleoid-associated protein (NAP) and illustration of DNA flexure angles at single-molecule resolution. Int J Biol Macromol 2021; 171:100-111. [PMID: 33418050 DOI: 10.1016/j.ijbiomac.2020.12.194] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2020] [Revised: 12/24/2020] [Accepted: 12/25/2020] [Indexed: 11/20/2022]
Abstract
Integration Host Factor (IHF) is a heterodimeric site-specific nucleoid-associated protein (NAP), well known for its DNA bending ability. Although the IHF induced bending states of DNA have been captured by both X-ray Crystallography and Atomic Force Microscopy (AFM), the range of flexibility and degree of heterogeneity in terms of quantitative analysis of the nucleoprotein complex has largely remained unexplored. Binding of IHF leads to introduction of two kinks in the dsDNA that allowed us to come up with a quadrilateral model. The findings have further been extended by calculating the angles of flexibility, that gives the idea of the degree of dynamicity of the nucleoprotein complex. We have monitored and compared the trajectories of the conformational dynamics of a dsDNA upon binding of wild-type (wt) and single-chain (sc) IHF at millisecond resolution through single-molecule FRET (smFRET). Our findings reveal that the nucleoprotein complex exists in a 'Slacked-Dynamic' state throughout the observation window where many of them have switched between multiple 'Wobbling States' in the course of attainment of packaged form. This study opens up an opportunity to improve the understanding of the functions of other nucleoid-associated proteins (NAPs) by complementing the previous detailed atomic-level structural analysis, which eventually will allow accessibility towards a better hypothesis.
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Affiliation(s)
- Debayan Purkait
- Single Molecule Biophysics Lab, Chemical Sciences Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata, India; Homi Bhaba National Institute (HBNI), Mumbai, India
| | - Debolina Bandyopadhyay
- Single Molecule Biophysics Lab, Chemical Sciences Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata, India; Homi Bhaba National Institute (HBNI), Mumbai, India
| | - Padmaja P Mishra
- Single Molecule Biophysics Lab, Chemical Sciences Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata, India; Homi Bhaba National Institute (HBNI), Mumbai, India.
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Chen Y, Zhan Z, Zhang H, Bi L, Zhang XE, Fu YV. Kinetic analysis of DNA compaction by mycobacterial integration host factor at the single-molecule level. Tuberculosis (Edinb) 2019; 119:101862. [PMID: 31733417 DOI: 10.1016/j.tube.2019.101862] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2019] [Revised: 08/14/2019] [Accepted: 09/08/2019] [Indexed: 11/19/2022]
Abstract
Nucleoid-associated proteins (NAPs) play an important role on chromosome condensation and organization. Mycobacterial integration host factor (mIHF) is one of the few mycobacterial NAPs identified so far. mIHF has the ability to stimulate mycobacteriophage L5 integration and compact DNA into nucleoid-like or higher order filamentous structures by atomic force microscopy observation. In this study, M. smegmatis IHF (MsIHF), which possesses the sequence essential for mIHF's functions, binds 30-bp dsDNA fragments in a sequence-independent manner and displays sensitivity to ion strength in bio-layer interferometry (BLI) experiments. The DNA compaction process of MsIHF was observed at the single-molecule level using the total internal reflection fluorescence microscopy (TIRFM). MsIHF efficiently compacted λ DNA into a highly condensed structure with the concentration of 0.25 and 1.0 μM, and the packing ratios were higher than 10. Further kinetic analysis revealed MsIHF compacts DNA in a three-step mechanism, which consists of two compaction steps with different compacting rates separated by a lag step. This study would help us better understand the mechanisms of chromosomal DNA organization in mycobacteria.
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Affiliation(s)
- Yuanyuan Chen
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China; University of Chinese Academy of Sciences, Beijing, 100049, China; Core Facility for Protein Research, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Zhengyan Zhan
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Hongtai Zhang
- Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Lijun Bi
- Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Xian-En Zhang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Yu Vincent Fu
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China; Savaid Medical School, University of Chinese Academy of Sciences, Beijing, 100049, China.
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Chen X, Yu C, Li S, Li X, Liu Q. Integration Host Factor Is Essential for Biofilm Formation, Extracellular Enzyme, Zeamine Production, and Virulence in Dickeya zeae. Mol Plant Microbe Interact 2019; 32:325-335. [PMID: 30226395 DOI: 10.1094/mpmi-04-18-0096-r] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Dickeya zeae is a globally important pathogenic bacterium that infects many crops, including rice, maize, potato, and banana. Bacterial foot rot of rice caused by D. zeae is one of the most important bacterial diseases of rice in China and some Southeast Asian countries. To investigate the functions of integration host factor (IHF) in D. zeae, we generated knockout mutants of ihfA and ihfB. Phenotypic assays showed that both the ΔihfA and ΔihfB strains had greatly reduced mobility, biofilm formation, extracellular protease, and pectinase activities, and toxin production compared with the wild-type strain. In addition, the mutants did not inhibit the germination of rice seeds, failed to cause soft rot in potatoes and a hypersensitive response in tobacco, and were avirulent in rice. Quantitative reverse-transcription polymerase chain reaction analysis demonstrated that IHF positively regulates the expression of zmsA, hrpN/Y, pelA/B/C, pehX, celZ, prtG, fliC, and DGC (diguanylate cyclase). Electrophoretic mobility shift assays further confirmed that IhfA binds to the promoter region of the DGC gene and may alter the levels of a second bacterial messenger, c-di-GMP, to regulate the pathogenicity or other physiological functions of D. zeae. In summary, IHF is an important integrated regulator of pathogenicity in D. zeae.
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Affiliation(s)
- Xuefeng Chen
- State Key Laboratory of Conservation and Utilization of Subtropical Agro-bioresources, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, College of Agriculture, South China Agricultural University, Guangzhou 510642, China
| | - Chengpeng Yu
- State Key Laboratory of Conservation and Utilization of Subtropical Agro-bioresources, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, College of Agriculture, South China Agricultural University, Guangzhou 510642, China
| | - Shuangchun Li
- State Key Laboratory of Conservation and Utilization of Subtropical Agro-bioresources, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, College of Agriculture, South China Agricultural University, Guangzhou 510642, China
| | - Xinwei Li
- State Key Laboratory of Conservation and Utilization of Subtropical Agro-bioresources, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, College of Agriculture, South China Agricultural University, Guangzhou 510642, China
| | - Qiongguang Liu
- State Key Laboratory of Conservation and Utilization of Subtropical Agro-bioresources, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, College of Agriculture, South China Agricultural University, Guangzhou 510642, China
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9
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Rollie C, Graham S, Rouillon C, White MF. Prespacer processing and specific integration in a Type I-A CRISPR system. Nucleic Acids Res 2018; 46:1007-1020. [PMID: 29228332 PMCID: PMC5815122 DOI: 10.1093/nar/gkx1232] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [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: 10/31/2017] [Revised: 11/22/2017] [Accepted: 11/29/2017] [Indexed: 12/15/2022] Open
Abstract
The CRISPR-Cas system for prokaryotic adaptive immunity provides RNA-mediated protection from viruses and mobile genetic elements. Adaptation is dependent on the Cas1 and Cas2 proteins along with varying accessory proteins. Here we analyse the process in Sulfolobus solfataricus, showing that while Cas1 and Cas2 catalyze spacer integration in vitro, host factors are required for specificity. Specific integration also requires at least 400 bp of the leader sequence, and is dependent on the presence of hydrolysable ATP, suggestive of an active process that may involve DNA remodelling. Specific spacer integration is associated with processing of prespacer 3' ends in a PAM-dependent manner. This is reflected in PAM-dependent processing of prespacer 3' ends in vitro in the presence of cell lysate or the Cas4 nuclease, in a reaction consistent with PAM-directed binding and protection of prespacer DNA. These results highlight the diverse interplay between CRISPR-Cas elements and host proteins across CRISPR types.
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Affiliation(s)
- Clare Rollie
- Biomedical Sciences Research Complex, School of Biology, University of St Andrews, North Haugh, St Andrews, Fife KY16 9ST, UK
| | - Shirley Graham
- Biomedical Sciences Research Complex, School of Biology, University of St Andrews, North Haugh, St Andrews, Fife KY16 9ST, UK
| | - Christophe Rouillon
- Biomedical Sciences Research Complex, School of Biology, University of St Andrews, North Haugh, St Andrews, Fife KY16 9ST, UK
| | - Malcolm F White
- Biomedical Sciences Research Complex, School of Biology, University of St Andrews, North Haugh, St Andrews, Fife KY16 9ST, UK
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10
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Lee JH, Zhao Y. Integration Host Factor Is Required for RpoN-Dependent hrpL Gene Expression and Controls Motility by Positively Regulating rsmB sRNA in Erwinia amylovora. Phytopathology 2016; 106:29-36. [PMID: 26368515 DOI: 10.1094/phyto-07-15-0170-r] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Erwinia amylovora requires an hrp-type III secretion system (T3SS) to cause disease. It has been reported that HrpL, the master regulator of T3SS, is transcriptionally regulated by sigma factor 54 (RpoN), YhbH, and HrpS. In this study, the role of integration host factor (IHF) in regulating hrpL and T3SS gene expression was investigated. IHF is a nucleoid-associated protein that regulates gene expression by influencing nucleoid structure and DNA bending. Our results showed that both ihfA and ihfB mutants of E. amylovora did not induce necrotic lesions on pear fruits. Growth of both mutants was greatly reduced, and expression of the hrpL and T3SS genes was significantly down-regulated as compared with those of the wild type. In addition, expression of the ihfA, but not the ihfB gene, was under auto-suppression by IHF. Furthermore, both ihfA and ihfB mutants were hypermotile, due to significantly reduced expression of small RNA (sRNA) rsmB. Electrophoresis mobility shift assay further confirmed that IHF binds to the promoters of the hrpL and ihfA genes, as well as the rsmB sRNA gene. These results indicate that IHF is required for RpoN-dependent hrpL gene expression and virulence, and controls motility by positively regulating the rsmB sRNA in E. amylovora.
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Affiliation(s)
- Jae Hoon Lee
- First and second authors: Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801
| | - Youfu Zhao
- First and second authors: Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801
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11
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Rendón MA, Hockenberry AM, McManus SA, So M. Sigma factor RpoN (σ54) regulates pilE transcription in commensal Neisseria elongata. Mol Microbiol 2013; 90:103-13. [PMID: 23899162 PMCID: PMC4474139 DOI: 10.1111/mmi.12350] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [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] [Accepted: 07/28/2013] [Indexed: 01/29/2023]
Abstract
Human-adapted Neisseria includes two pathogens, Neisseria gonorrhoeae and Neisseria meningitidis, and at least 13 species of commensals that colonize many of the same niches as the pathogens. The Type IV pilus plays an important role in the biology of pathogenic Neisseria. In these species, Sigma factor RpoD (σ(70)), Integration Host Factor, and repressors RegF and CrgA regulate transcription of pilE, the gene encoding the pilus structural subunit. The Type IV pilus is also a strictly conserved trait in commensal Neisseria. We present evidence that a different mechanism regulates pilE transcription in commensals. Using Neisseria elongata as a model, we show that Sigma factor RpoN (σ(54)), Integration Host Factor, and an activator we name Npa regulate pilE transcription. Taken in context with previous reports, our findings indicate pilE regulation switched from an RpoN- to an RpoD-dependent mechanism as pathogenic Neisseria diverged from commensals during evolution. Our findings have implications for the timing of Tfp expression and Tfp-mediated host cell interactions in these two groups of bacteria.
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Affiliation(s)
- María A. Rendón
- The BIO5 Institute, University of Arizona, Tucson, AZ 85721, USA
- Department of Immunobiology, University of Arizona, Tucson, AZ 85721, USA
| | - Alyson M. Hockenberry
- The BIO5 Institute, University of Arizona, Tucson, AZ 85721, USA
- Department of Immunobiology, University of Arizona, Tucson, AZ 85721, USA
| | - Steven A. McManus
- Undergraduate Biology Research Program, University of Arizona, Tucson, AZ 85721, USA
| | - Magdalene So
- The BIO5 Institute, University of Arizona, Tucson, AZ 85721, USA
- Department of Immunobiology, University of Arizona, Tucson, AZ 85721, USA
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12
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Cagliero C, Jin DJ. Dissociation and re-association of RNA polymerase with DNA during osmotic stress response in Escherichia coli. Nucleic Acids Res 2013; 41:315-26. [PMID: 23093594 PMCID: PMC3592413 DOI: 10.1093/nar/gks988] [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] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2012] [Revised: 09/26/2012] [Accepted: 09/27/2012] [Indexed: 11/12/2022] Open
Abstract
The thermodynamic association of RNA polymerase (RNAP) with DNA is sensitive to salt concentration in vitro. Paradoxically, previous studies of changes in osmolarity during steady-state cell growth found no dependence between the association of RNAP to DNA and K(+) concentration in Escherichia coli. We reevaluated this issue by following the interaction of RNAP and genomic DNA in time-course experiments during the hyper-osmotic response. Our results show that the interaction is temporally controlled by the same physical chemistry principle in the cell as in vitro. RNAP rapidly dissociates from the genome during the initial response when the cytoplasmic K(+) accumulates transiently, and concurrently the nucleoid becomes hyper-condensed. The freed RNAP re-associates with the genome during a subsequent osmoadaptation phase when organic osmoprotectants accumulate as K(+) levels decrease. RNAP first surrounds the hyper-condensed nucleoid forming a sphere of RNAP before it progressively moves in to the center of the nucleoid. Our findings reinterpret the dynamic protein-DNA interactions during osmotic stress response. We discuss the implications of the dissociation/association of RNAP for osmotic protection and nucleoid structure.
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Affiliation(s)
| | - Ding Jun Jin
- Transcription control section, Gene Regulation and Chromosome Biology Laboratory, Frederick National Laboratory for Cancer Research, National Cancer Institute, National Institutes of Health, Frederick, MD, USA
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13
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Lin J, Chen H, Dröge P, Yan J. Physical organization of DNA by multiple non-specific DNA-binding modes of integration host factor (IHF). PLoS One 2012; 7:e49885. [PMID: 23166787 PMCID: PMC3498176 DOI: 10.1371/journal.pone.0049885] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Accepted: 10/15/2012] [Indexed: 11/18/2022] Open
Abstract
The integration host factor (IHF) is an abundant nucleoid-associated protein and an essential co-factor for phage λ site-specific recombination and gene regulation in E. coli. Introduction of a sharp DNA kink at specific cognate sites is critical for these functions. Interestingly, the intracellular concentration of IHF is much higher than the concentration needed for site-specific interactions, suggesting that non-specific binding of IHF to DNA plays a role in the physical organization of bacterial chromatin. However, it is unclear how non-specific DNA association contributes to DNA organization. By using a combination of single DNA manipulation and atomic force microscopy imaging methods, we show here that distinct modes of non-specific DNA binding of IHF result in complex global DNA conformations. Changes in KCl and IHF concentrations, as well as tension applied to DNA, dramatically influence the degree of DNA-bending. In addition, IHF can crosslink DNA into a highly compact DNA meshwork that is observed in the presence of magnesium at low concentration of monovalent ions and high IHF-DNA stoichiometries. Our findings provide important insights into how IHF contributes to bacterial chromatin organization, gene regulation, and biofilm formation.
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Affiliation(s)
- Jie Lin
- Department of Physics, National University of Singapore, Singapore, Singapore
- Mechanobiology Institute, National University of Singapore, Singapore, Singapore
- Centre for Bioimaging Sciences, National University of Singapore, Singapore, Singapore
| | - Hu Chen
- Mechanobiology Institute, National University of Singapore, Singapore, Singapore
| | - Peter Dröge
- Division of Molecular Genetics and Cell Biology, School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
- * E-mail: (PD); (JY)
| | - Jie Yan
- Department of Physics, National University of Singapore, Singapore, Singapore
- Mechanobiology Institute, National University of Singapore, Singapore, Singapore
- Centre for Bioimaging Sciences, National University of Singapore, Singapore, Singapore
- * E-mail: (PD); (JY)
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14
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Prieto AI, Kahramanoglou C, Ali RM, Fraser GM, Seshasayee ASN, Luscombe NM. Genomic analysis of DNA binding and gene regulation by homologous nucleoid-associated proteins IHF and HU in Escherichia coli K12. Nucleic Acids Res 2012; 40:3524-37. [PMID: 22180530 PMCID: PMC3333857 DOI: 10.1093/nar/gkr1236] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.9] [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: 10/18/2011] [Revised: 11/24/2011] [Accepted: 11/28/2011] [Indexed: 11/18/2022] Open
Abstract
IHF and HU are two heterodimeric nucleoid-associated proteins (NAP) that belong to the same protein family but interact differently with the DNA. IHF is a sequence-specific DNA-binding protein that bends the DNA by over 160°. HU is the most conserved NAP, which binds non-specifically to duplex DNA with a particular preference for targeting nicked and bent DNA. Despite their importance, the in vivo interactions of the two proteins to the DNA remain to be described at a high resolution and on a genome-wide scale. Further, the effects of these proteins on gene expression on a global scale remain contentious. Finally, the contrast between the functions of the homo- and heterodimeric forms of proteins deserves the attention of further study. Here we present a genome-scale study of HU- and IHF binding to the Escherichia coli K12 chromosome using ChIP-seq. We also perform microarray analysis of gene expression in single- and double-deletion mutants of each protein to identify their regulons. The sequence-specific binding profile of IHF encompasses ∼30% of all operons, though the expression of <10% of these is affected by its deletion suggesting combinatorial control or a molecular backup. The binding profile for HU is reflective of relatively non-specific binding to the chromosome, however, with a preference for A/T-rich DNA. The HU regulon comprises highly conserved genes including those that are essential and possibly supercoiling sensitive. Finally, by performing ChIP-seq experiments, where possible, of each subunit of IHF and HU in the absence of the other subunit, we define genome-wide maps of DNA binding of the proteins in their hetero- and homodimeric forms.
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Affiliation(s)
- Ana I. Prieto
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, EMBL-European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SD, MRC-National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK, Centre for Biotechnology, Anna University, Chennai 600 035, National Centre for Biological Sciences, GKVK, Bellary Road, Bangalore 560 065, India and Okinawa Institute of Science and Technology, Tancha, Onna-son, Kunigami-gun, Okinawa 904-0495, Japan
| | - Christina Kahramanoglou
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, EMBL-European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SD, MRC-National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK, Centre for Biotechnology, Anna University, Chennai 600 035, National Centre for Biological Sciences, GKVK, Bellary Road, Bangalore 560 065, India and Okinawa Institute of Science and Technology, Tancha, Onna-son, Kunigami-gun, Okinawa 904-0495, Japan
| | - Ruhi M. Ali
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, EMBL-European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SD, MRC-National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK, Centre for Biotechnology, Anna University, Chennai 600 035, National Centre for Biological Sciences, GKVK, Bellary Road, Bangalore 560 065, India and Okinawa Institute of Science and Technology, Tancha, Onna-son, Kunigami-gun, Okinawa 904-0495, Japan
| | - Gillian M. Fraser
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, EMBL-European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SD, MRC-National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK, Centre for Biotechnology, Anna University, Chennai 600 035, National Centre for Biological Sciences, GKVK, Bellary Road, Bangalore 560 065, India and Okinawa Institute of Science and Technology, Tancha, Onna-son, Kunigami-gun, Okinawa 904-0495, Japan
| | - Aswin S. N. Seshasayee
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, EMBL-European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SD, MRC-National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK, Centre for Biotechnology, Anna University, Chennai 600 035, National Centre for Biological Sciences, GKVK, Bellary Road, Bangalore 560 065, India and Okinawa Institute of Science and Technology, Tancha, Onna-son, Kunigami-gun, Okinawa 904-0495, Japan
| | - Nicholas M. Luscombe
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, EMBL-European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SD, MRC-National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK, Centre for Biotechnology, Anna University, Chennai 600 035, National Centre for Biological Sciences, GKVK, Bellary Road, Bangalore 560 065, India and Okinawa Institute of Science and Technology, Tancha, Onna-son, Kunigami-gun, Okinawa 904-0495, Japan
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15
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Queiroz MH, Madrid C, Paytubi S, Balsalobre C, Juárez A. Integration host factor alleviates H-NS silencing of the Salmonella enterica serovar Typhimurium master regulator of SPI1, hilA. Microbiology (Reading) 2011; 157:2504-2514. [PMID: 21680637 DOI: 10.1099/mic.0.049197-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Coordination of the expression of Salmonella enterica invasion genes on Salmonella pathogenicity island 1 (SPI1) depends on a complex circuit involving several regulators that converge on expression of the hilA gene, which encodes a transcriptional activator (HilA) that modulates expression of the SPI1 virulence genes. Two of the global regulators that influence hilA expression are the nucleoid-associated proteins Hha and H-NS. They interact and form a complex that modulates gene expression. A chromosomal transcriptional fusion was constructed to assess the effects of these modulators on hilA transcription under several environmental conditions as well as at different stages of growth. The results obtained showed that these proteins play a role in silencing hilA expression at both low temperature and low osmolarity, irrespective of the growth phase. H-NS accounts for the main repressor activity. At high temperature and osmolarity, H-NS-mediated silencing completely ceases when cells enter the stationary phase, and hilA expression is induced. Mutants lacking IHF did not induce hilA in cells entering the stationary phase, and this lack of induction was dependent on the presence of H-NS. Band-shift assays and in vitro transcription data showed that for hilA induction under certain growth conditions, IHF is required to alleviate H-NS-mediated silencing.
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Affiliation(s)
- Mário H Queiroz
- Departament de Microbiologia, Facultat de Biologia, Universitat de Barcelona, Avda Diagonal, 645, 08028 Barcelona, Spain
| | - Cristina Madrid
- Departament de Microbiologia, Facultat de Biologia, Universitat de Barcelona, Avda Diagonal, 645, 08028 Barcelona, Spain
| | - Sònia Paytubi
- Departament de Microbiologia, Facultat de Biologia, Universitat de Barcelona, Avda Diagonal, 645, 08028 Barcelona, Spain
| | - Carlos Balsalobre
- Departament de Microbiologia, Facultat de Biologia, Universitat de Barcelona, Avda Diagonal, 645, 08028 Barcelona, Spain
| | - Antonio Juárez
- Institut de Bioenginyeria de Catalunya (IBEC), Parc Científic de Barcelona, Baldiri Reixach, 15-21, 08028 Barcelona, Spain
- Departament de Microbiologia, Facultat de Biologia, Universitat de Barcelona, Avda Diagonal, 645, 08028 Barcelona, Spain
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16
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Cao D, Haussecker D, Huang Y, Kay MA. Combined proteomic-RNAi screen for host factors involved in human hepatitis delta virus replication. RNA 2009; 15:1971-9. [PMID: 19776158 PMCID: PMC2764473 DOI: 10.1261/rna.1782209] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Human hepatitis delta virus (HDV) is the only animal virus known to replicate its RNA genome using a host polymerase because its only virally encoded proteins, the small and large hepatitis delta antigens (HDAg-S and HDAg-L), lack polymerase activity. Although this makes HDV an ideal model system to study RNA-directed transcription in mammalian cells, little is known about the host factors involved in its replication. To comprehensively identify such host factors, we created a stable cell line carrying a functional FLAG-HDAg-S. Anti-Flag immunopurification and mass spectrometry identified >100 proteins associated with FLAG-HDAg-S, many of which had predicted roles in RNA metabolism. The biological relevance of this screen was strongly supported by the identification of nine out of the 12 subunits of the RNA polymerase II complex thought to mediate HDV replication. To further investigate the significance of these factors for HDV replication, we selected 65 proteins to look for factors that would also affect the accumulation of HDV RNA following siRNA knockdown. Fifteen and three factors were found to regulate HDV RNA accumulation negatively and positively, respectively, upon RNAi knockdown. Our results provide a valuable resource for future research to advance our mechanistic understanding of HDV replication and RNA-directed transcription in mammalian cells.
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17
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Abstract
Transposable Insertion Sequences (IS elements) have been shown to provide various benefits to their hosts via gene activation or inactivation under stress conditions by appropriately inserting into specific chromosomal sites. Activation is usually due to derepression or introduction of a complete or partial promoter located within the element. Here we define a novel mechanism of gene activation by the transposon IS5 in Escherichia coli. The glycerol utilization operon, glpFK, that is silent in the absence of the cAMP-Crp complex, is activated by IS5 when inserted upstream of its promoter. High-level expression is nearly constitutive, only mildly dependent on glycerol, glucose, GlpR, and Crp, and allows growth at a rate similar to or more rapid than that of wild-type cells. Expression is from the glpFK promoter and dependent on (1) the DNA phase, (2) integration host factor (IHF), and (3) a short region at the 3′ end of IS5 harboring a permanent bend and an IHF binding site. The lacZYA operon is also subject to such activation in the absence of Crp. Thus, we have defined a novel mechanism of gene activation involving transposon insertion that may be generally applicable to many organisms. Transposons are “jumping genes” that can move from one location within a genome to another. Insertion of a transponson changes the DNA sequence and therefore gives rise to mutations that can activate or inactivate gene expression. Here, we demonstrate for the first time that one such transposon, Insertion Sequence 5 (IS5), when positioned upstream of a metabolic operon (glpFK) of E. coli, can activate the otherwise cryptic expression of the operon. This effect is due solely to a short region at the 3′ end of IS5 that harbors a permanent bend and an overlapping nucleoid protein binding site, both of which are required for maximal gene expression. We demonstrate the importance of phasing and conclude that DNA looping probably plays a role. We also show that another operon, the E. coli lactose operon (lacZYA), can be similarly activated by IS5. Although this is the first study to show that unique sequences within a transposon are necessary and sufficient to activate a downstream silent promoter, similar mechanisms of gene activation may occur for other operons.
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Affiliation(s)
- Zhongge Zhang
- Division of Biological Sciences, University of California San Diego, La Jolla, California, United States of America
| | - Milton H. Saier
- Division of Biological Sciences, University of California San Diego, La Jolla, California, United States of America
- * E-mail:
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18
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Abstract
We present a model of nonspecific cooperative binding of proteins to DNA in which the binding of isolated proteins generates local bends but binding of proteins at neighboring sites on DNA straightens the polymer. We solve the statistical mechanical problem and calculate the effective persistence length, site occupancy, and cooperativity. Cooperativity leads to nonmonotonic variation of the persistence length with protein concentration, and to an unusual shape of the binding isotherm. The results are in qualitative agreement with recent single molecule experiments on nucleoid protein HU-DNA complexes.
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Affiliation(s)
- S M Rappaport
- Department of Physics, Bar-Ilan University, Ramat-Gan 52900, Israel
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19
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Thomas NA, Deng W, Baker N, Puente J, Finlay BB. Hierarchical Delivery of an Essential Host Colonization Factor in Enteropathogenic Escherichia coli. J Biol Chem 2007; 282:29634-45. [PMID: 17681945 DOI: 10.1074/jbc.m706019200] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [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: 12/29/2022] Open
Abstract
Many significant bacterial pathogens use a type III secretion system to inject effector proteins into host cells to disrupt specific cellular functions, enabling disease progression. The injection of these effectors into host cells is often dependent on dedicated chaperones within the bacterial cell. In this report, we demonstrate that the enteropathogenic Escherichia coli (EPEC) chaperone CesT interacts with a variety of known and putative type III effector proteins. Using pull-down and secretion assays, a degenerate CesT binding domain was identified within multiple type III effectors. Domain exchange experiments between selected type III effector proteins revealed a modular nature for the CesT binding domain, as demonstrated by secretion, chaperone binding, and infection assays. The CesT-interacting type III effector Tir, which is crucial for in vivo intestinal colonization, had to be expressed and secreted for efficient secretion of other type III effectors. In contrast, the absence of other CesT-interacting type III effectors did not abrogate effector secretion, indicating an unexpected hierarchy with respect to Tir for type III effector delivery. Coordinating the expression of other type III effectors with cesT in the absence of tir partially restored total type III effector secretion, thereby implicating CesT in secretion events. Collectively, the results suggest a coordinated mechanism involving both Tir and CesT for type III effector injection into host cells.
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Affiliation(s)
- Nikhil A Thomas
- Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4.
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20
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Abstract
In bacteria, many DNA-protein interactions that initiate transcription, replication and recombination require the mediation of DNA architectural proteins such as IHF and HU. For replication initiation, plasmid P1 requires three origin binding proteins: the architectural protein HU, a plasmid-specific initiator, RepA, and the Escherichia coli chromosomal initiator, DnaA. The two initiators bind in the origin of replication to multiple sites, called iterons and DnaA boxes respectively. We show here that all five known DnaA boxes can be deleted from the plasmid origin provided the origin is extended by about 120 bp. The additional DNA provides an IHF site and most likely a weak DnaA binding site, because replacing the putative site with an authentic DnaA box enhanced plasmid replication in an IHF-dependent manner. IHF most likely brings about interactions between distally bound DnaA and RepA by bending the intervening DNA. The role of IHF in activating P1 origin by allowing DnaA binding to a weak site is reminiscent of the role the protein plays in initiating the host chromosomal replication.
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Affiliation(s)
- Richard A Fekete
- Laboratory of Biochemistry, Center for Cancer Research, NCI, NIH, Bethesda, MD 20892-4255, USA
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21
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Abstract
Molecular beacon detection of equilibrium cyclization (MBEC) is a novel, high sensitivity technique that can allow DNA-protein complex formation to be studied under diverse conditions in a cost effective and rapid manner that can be adapted to high throughput screening. To demonstrate the ease and utility of applying MBEC to the investigation of the K(D) values of protein-DNA complexes, the sequence-specific Escherichia coli integration host factor (IHF) protein has been used as a test system. Competition between a labeled MBEC DNA construct and unlabeled duplex DNA for IHF binding allows the determination of K(D) values as a function of the DNA duplex sequence. This allows sequence specificity to be monitored while using only a single molecular beacon-labeled DNA. The robustness of MBEC for monitoring protein-DNA complex formation has been further demonstrated by determining the K(D) values as a function of salt concentration to investigate the net number of salt bridges formed in sequence-specific and -nonspecific IHF-DNA complexes. These MBEC results have been compared with those from other approaches.
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Affiliation(s)
- Jason Vitko
- Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, Connecticut 06459, USA
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22
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Jauréguy F, Carbonnelle E, Bonacorsi S, Clec'h C, Casassus P, Bingen E, Picard B, Nassif X, Lortholary O. Host and bacterial determinants of initial severity and outcome of Escherichia coli sepsis. Clin Microbiol Infect 2007; 13:854-62. [PMID: 17617183 DOI: 10.1111/j.1469-0691.2007.01775.x] [Citation(s) in RCA: 72] [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: 11/29/2022]
Abstract
A 1-year prospective cohort study of all episodes of Escherichia coli bacteraemia in two French university hospitals was conducted to assess simultaneously the influence of host and bacterial determinants on the initial severity and outcome of E. coli sepsis. Clinical data (community-acquired/nosocomial infection, immune status, underlying disease, primary source of infection, severity sepsis scoring and outcome), phylogenetic groups (A, B1, D and B2), nine virulence factors (VFs) (papC, papGII, papGIII, sfa/foc, hlyC, cnf1, iucC, fyuA and iroN) and the antibiotic susceptibility of isolates were investigated. All VFs except iucC were significantly more prevalent (p <0.05) among the B2 group isolates. The non-B2 isolates were more frequently resistant to antibiotics than were B2 isolates (p <0.05). There were significantly more B2 isolates from immunocompetent than from immunocompromised patients (p <0.05). No bacterial or host determinants influenced the initial severity of sepsis. Multivariate analysis revealed that the presence of papGIII, septic shock at baseline and a non-urinary tract origin of sepsis were associated independently with a fatal outcome (p 0.04, <0.0001 and 0.04, respectively). A factorial analysis of correspondence allowed two populations of isolates to be distinguished: those belonging to the B2 group were associated more frequently with susceptibility to antibiotics, community-acquired infection, a urinary tract origin and immunocompetent hosts; those belonging to the A, B1 or D groups were associated more frequently with resistance to antibiotics, a nosocomial origin, a non-urinary tract source and immunocompromised hosts. Although no influence of host or bacterial determinants on the initial severity of sepsis was detected, bacterial and host determinants both influenced the outcome of E. coli sepsis significantly.
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Affiliation(s)
- F Jauréguy
- Hôpital Avicenne, AP-HP, UFR Santé, Médecine, Biologie Humaine, Université Paris 13, and INSERM Unité 570, Faculté de Médecine Necker-Enfants Malades, Université Paris 5, Paris, France
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23
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Sclavi B, Beatty CM, Thach DS, Fredericks CE, Buckle M, Wolfe AJ. The multiple roles of CRP at the complex acs promoter depend on activation region 2 and IHF. Mol Microbiol 2007; 65:425-40. [PMID: 17630973 DOI: 10.1111/j.1365-2958.2007.05797.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [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: 12/21/2022]
Abstract
acs encodes a high-affinity enzyme that permits survival during carbon starvation. As befits a survival gene, its transcription is subject to complex regulation. Previously, we reported that cAMP receptor protein (CRP) activates acs transcription by binding tandem DNA sites located upstream of the major acsP2 promoter and that the nucleoid protein IHF (integration host factor) binds three specific sites located just upstream. In vivo, the sequence that includes these IHF sites exerts a positive effect on CRP-dependent transcription, while a construct containing only the most proximal site exhibits reduced transcription compared with the full-length promoter or with a construct lacking all three IHF sites. Here, we defined the minimal system required for this IHF-dependent inhibition, showing it requires the promoter-distal CRP site and an amino acid residue located within activation region 2 (AR2), a surface determinant of CRP that interacts with RNA polymerase (RNAP). Surprisingly, for a Class III promoter, disruption of AR2 caused significant changes in the activity and structure of both the full-length promoter and the construct with the single proximal IHF site. We propose that AR2, together with IHF, mediates formation of a multi-protein complex, in which RNAP is stabilized in an open complex that remains poised on the promoter ready to respond rapidly to environmental changes.
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Affiliation(s)
- Bianca Sclavi
- LBPA, UMR8113, CNRS/Ecole Normale Supérieure de Cachan, 94230 Cachan, France
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24
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Maxwell PH, Curcio MJ. Host factors that control long terminal repeat retrotransposons in Saccharomyces cerevisiae: implications for regulation of mammalian retroviruses. Eukaryot Cell 2007; 6:1069-80. [PMID: 17496126 PMCID: PMC1951103 DOI: 10.1128/ec.00092-07] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Patrick H Maxwell
- Center for Medical Sciences, Wadsworth Center, PO Box 2002, Albany, NY 12201-2002, USA
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25
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Sohanpal BK, Friar S, Roobol J, Plumbridge JA, Blomfield IC. Multiple co-regulatory elements and IHF are necessary for the control of fimB expression in response to sialic acid and N-acetylglucosamine in Escherichia coli K-12. Mol Microbiol 2007; 63:1223-36. [PMID: 17238917 DOI: 10.1111/j.1365-2958.2006.05583.x] [Citation(s) in RCA: 36] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Expression of the FimB recombinase, and hence the OFF-to-ON switching of type 1 fimbriation in Escherichia coli, is inhibited by sialic acid (Neu(5)Ac) and by GlcNAc. NanR (Neu(5)Ac-responsive) and NagC (GlcNAc-6P-responsive) activate fimB expression by binding to operators (O(NR) and O(NC1) respectively) located more than 600 bp upstream of the fimB promoter within the large (1.4 kb) nanC-fimB intergenic region. Here it is demonstrated that NagC binding to a second site (O(NC2)), located 212 bp closer to fimB, also controls fimB expression, and that integration host factor (IHF), which binds midway between O(NC1) and O(NC2), facilitates NagC binding to its two operator sites. In contrast, IHF does not enhance the ability of NanR to activate fimB expression in the wild-type background. Neither sequences up to 820 bp upstream of O(NR), nor those 270 bp downstream of O(NC2), are required for activation by NanR and NagC. However, placing the NanR, IHF and NagC binding sites closer to the fimB promoter enhances the ability of the regulators to activate fimB expression. These results support a refined model for how two potentially key indicators of host inflammation, Neu(5)Ac and GlcNAc, regulate type 1 fimbriation.
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Affiliation(s)
- Baljinder K Sohanpal
- Biomedical Research Group, Department of Biosciences, University of Kent, Kent, UK
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26
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Abstract
The nifA gene fulfills an essential role in the regulation of nitrogen fixation genes in Rhizobium etli. Transcription analysis of the nifA gene, assessed using promoter deletions, indicated an oxygen-independent expression, threefold higher during symbiosis as compared with free-living conditions. Electrophoretic mobility shift assays using those nifA promoter deletion fragments, which were actively transcribed, demonstrated the specific interaction with R. etli cellular protein(s) resulting in the formation of two DNA-protein complexes. An interacting protein was purified by liquid chromatography on Heparin Sepharose and Mono S columns. The purified 12 kDa R. etli protein cross-reacted with antibodies directed against Escherichia coli integration host factor (IHF). Furthermore, purified E. coli IHF was able to specifically bind to the R. etli nifA promoter region. These results point to an as yet undisclosed function of IHF in the regulation of R. etli nifA expression.
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Affiliation(s)
- Traki Benhassine
- Laboratoire de Biologie Cellulaire et Moléculaire, Faculté des Sciences Biologiques, USTHB, Alger, Algérie
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27
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Zurla C, Samuely T, Bertoni G, Valle F, Dietler G, Finzi L, Dunlap DD. Integration host factor alters LacI-induced DNA looping. Biophys Chem 2007; 128:245-52. [PMID: 17543441 DOI: 10.1016/j.bpc.2007.04.012] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2007] [Revised: 04/20/2007] [Accepted: 04/20/2007] [Indexed: 11/25/2022]
Abstract
The integration host factor protein of Escherichia coli, which sharply bends DNA at specific sites and non-specifically compacts the bacterial genome, can also alter looping of DNA in an artificial system based on the lactose repressor protein of E. coli. In single molecule experiments, we show that both specific bending and non-specific compaction alter LacI-mediated looping of DNA. Our results highlight the subtle regulatory roles that proteins, which confer structure upon DNA, might have in controlling DNA transcription and other processes in which the conformation of DNA determines the binding and activity of processive enzymes.
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Affiliation(s)
- Chiara Zurla
- Department of Physics, Emory University, Atlanta, GA 30322, USA
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28
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Williams SL, Schildbach JF. TraY and integration host factor oriT binding sites and F conjugal transfer: sequence variations, but not altered spacing, are tolerated. J Bacteriol 2007; 189:3813-23. [PMID: 17351033 PMCID: PMC1913323 DOI: 10.1128/jb.01783-06] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [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
Bacterial conjugation is the process by which a single strand of a conjugative plasmid is transferred from donor to recipient. For F plasmid, TraI, a relaxase or nickase, binds a single plasmid DNA strand at its specific origin of transfer (oriT) binding site, sbi, and cleaves at a site called nic. In vitro studies suggest TraI is recruited to sbi by its accessory proteins, TraY and integration host factor (IHF). TraY and IHF bind conserved oriT sites sbyA and ihfA, respectively, and bend DNA. The resulting conformational changes may propagate to nic, generating the single-stranded region that TraI can bind. Previous deletion studies performed by others showed transfer efficiency of a plasmid containing F oriT decreased progressively as increasingly longer segments, ultimately containing both sbyA and ihfA, were deleted. Here we describe our efforts to more precisely define the role of sbyA and ihfA by examining the effects of multiple base substitutions at sbyA and ihfA on binding and plasmid mobilization. While we observed significant decreases in in vitro DNA-binding affinities, we saw little effect on plasmid mobilization even when sbyA and ihfA variants were combined. In contrast, when half or full helical turns were inserted between the relaxosome protein-binding sites, mobilization was dramatically reduced, in some cases below the detectable limit of the assay. These results are consistent with TraY and IHF recognizing sbyA and ihfA with limited sequence specificity and with relaxosome proteins requiring proper spacing and orientation with respect to each other.
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Affiliation(s)
- Sarah L Williams
- Department of Biology, The Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
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29
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Abstract
Phage Mu is the most efficient transposable element known, its high efficiency being conferred by an enhancer DNA element. Transposition is the end result of a series of well choreographed steps that juxtapose the enhancer and the two Mu ends within a nucleoprotein complex called the 'transpososome.' The particular arrangement of DNA and protein components lends extraordinary stability to the transpososome and regulates the frequency, precision, directionality, and mechanism of transposition. The structure of the transpososome, therefore, holds the key to understanding all of these attributes, and ultimately to explaining the runaway genetic success of transposable elements throughout the biological world. This review focuses on the path of the DNA within the Mu transpososome, as uncovered by recent topological analyses. It discusses why Mu topology cannot be analyzed by standard methods, and how knowledge of the geometry of site alignment during Flp and Cre site-specific recombination was harnessed to design a new methodology called 'difference topology.' This methodology has also revealed the order and dynamics of association of the three interacting DNA sites, as well as the role of the enhancer in assembly of the Mu transpososome.
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Affiliation(s)
- Rasika M Harshey
- Section of Molecular Genetics and Microbiology & Institute of Cellular and Molecular Biology, University of Texas at Austin, TX, USA.
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30
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Abstract
Tn10 is a bacterial transposon that transposes through a non-replicative mechanism. This mode of DNA transposition is widely used in bacteria and is also used by "DNA-based" transposons in eukaryotes. Tn10 has served as a paradigm for this mode of transposition and continues to provide novel insights into how steps in transposition reactions occur and how these steps are regulated. A common feature of transposition reactions is that they require the formation of a higher order protein-DNA complex called a transpososome. A major objective in the last few years has been to better understand the dynamics of transpososome assembly and progression through the course of transposition reactions. This problem is particularly interesting in the Tn10 system because two important host proteins, IHF and H-NS, have been implicated in regulating transpososome assembly and/or function. Interestingly, H-NS is an integral part of stress response pathways in bacteria, and its function is known to be sensitive to changes in environmental conditions. Consequently, H-NS may provide a means of allowing Tn10 to responed to changing environmental conditions. The current review focuses on the roles of both IHF and H-NS on Tn10 transposition.
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Affiliation(s)
- David B Haniford
- Department of Biochemistry, University of Western Ontario, London, Ontario, Canada.
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31
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Ragonese H, Haisch D, Villareal E, Choi JH, Matson SW. The F plasmid‐encoded TraM protein stimulates relaxosome‐mediated cleavage atoriTthrough an interaction with TraI. Mol Microbiol 2007; 63:1173-84. [PMID: 17238924 DOI: 10.1111/j.1365-2958.2006.05576.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [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: 11/28/2022]
Abstract
Conjugative DNA transfer is a highly conserved process for the direct transfer of DNA from a donor to a recipient. The conjugative initiator proteins are key players in the DNA processing reactions that initiate DNA transfer - they introduce a site- and strand-specific break in the DNA backbone via a transesterification that leaves the initiator protein covalently bound on the 5'-end of the cleaved DNA strand. The action of the initiator protein at the origin of transfer (oriT) is governed by auxiliary proteins that alter the architecture of the DNA molecule, allowing binding of the initiator protein. In the F plasmid system, two auxiliary proteins have roles in establishing the relaxosome: the host-encoded IHF and the plasmid-encoded TraY. Together, these proteins direct the loading of TraI which contains the catalytic centre for the transesterification. The F-oriT sequence includes a binding site for another plasmid-encoded protein, TraM, which is required for DNA transfer. Here the impact of TraM protein on the formation and activity of the F plasmid relaxosome has been examined. Purified TraM stimulates the formation of relaxed DNA in a reaction that requires the minimal components of the relaxosome, TraI, TraY and IHF. Unlike TraY and IHF, TraM is not essential for the formation of the relaxosome in vitro and TraM cannot substitute for either TraY or IHF in this process. The TraM binding site sbmC, along with both IHF binding sites, is essential for stimulation of the relaxase reaction. In addition, stimulation of transesterification appears to require the C-terminal domain of TraI suggesting that TraM and TraI may interact through this domain on TraI. Taken together, these results provide additional evidence of a role for TraM as a component of the relaxosome, suggest a previously unknown interaction between TraI and TraM, and allow us to propose a molecular role for the C-terminal domain of TraI.
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Affiliation(s)
- Heather Ragonese
- Department of Biology, University of North Carolina at Chapel Hill, NC 27599, USA
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32
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Aeling KA, Steffen NR, Johnson M, Hatfield GW, Lathrop RH, Senear DF. DNA deformation energy as an indirect recognition mechanism in protein-DNA interactions. IEEE/ACM Trans Comput Biol Bioinform 2007; 4:117-25. [PMID: 17277419 DOI: 10.1109/tcbb.2007.1000] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Proteins that bind to specific locations in genomic DNA control many basic cellular functions. Proteins detect their binding sites using both direct and indirect recognition mechanisms. Deformation energy, which models the energy required to bend DNA from its native shape to its shape when bound to a protein, has been shown to be an indirect recognition mechanism for one particular protein, Integration Host Factor (IHF). This work extends the analysis of deformation to two other DNA-binding proteins, CRP and SRF, and two endonucleases, I-CreI and I-PpoI. Known binding sites for all five proteins showed statistically significant differences in mean deformation energy as compared to random sequences. Binding sites for the three DNA-binding proteins and one of the endonucleases had mean deformation energies lower than random sequences. Binding sites for I-PpoI had mean deformation energy higher than random sequences. Classifiers that were trained using the deformation energy at each base pair step showed good cross-validated accuracy when classifying unseen sequences as binders or nonbinders. These results support DNA deformation energy as an indirect recognition mechanism across a wider range of DNA-binding proteins. Deformation energy may also have a predictive capacity for the underlying catalytic mechanism of DNA-binding enzymes.
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MESH Headings
- Algorithms
- Animals
- Base Sequence
- Binding Sites
- Cyclic AMP Receptor Protein/chemistry
- Cyclic AMP Receptor Protein/metabolism
- DNA/chemistry
- DNA/genetics
- DNA/metabolism
- DNA Restriction Enzymes/chemistry
- DNA Restriction Enzymes/metabolism
- DNA, Algal/chemistry
- DNA, Algal/genetics
- DNA, Algal/metabolism
- DNA, Bacterial/chemistry
- DNA, Bacterial/genetics
- DNA, Bacterial/metabolism
- DNA, Protozoan/chemistry
- DNA, Protozoan/genetics
- DNA, Protozoan/metabolism
- DNA-Binding Proteins/chemistry
- DNA-Binding Proteins/metabolism
- Endodeoxyribonucleases/chemistry
- Endodeoxyribonucleases/metabolism
- Humans
- Integration Host Factors/chemistry
- Integration Host Factors/metabolism
- Models, Chemical
- Models, Molecular
- Protein Binding
- Serum Response Factor/chemistry
- Serum Response Factor/metabolism
- Thermodynamics
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Affiliation(s)
- Kimberly A Aeling
- Department of Microbiology and Molecular Genetics, School of Medicine, University of California, Irvine, 92697-3425, USA.
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33
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Affiliation(s)
- Sergei Khrapunov
- *Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461
| | - Michael Brenowitz
- *Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461
| | - Phoebe A. Rice
- Department of Biochemistry and Molecular Biology, University of Chicago, 929 East 57th Street, Chicago, IL 60637; and
| | - Carlos Enrique Catalano
- Department of Medicinal Chemistry, University of Washington School of Pharmacy, H172 Health Sciences Building, Box 357610, Seattle, WA 98195
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34
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Rego FGM, Pedrosa FO, Chubatsu LS, Yates MG, Wassem R, Steffens MBR, Rigo LU, Souza EM. The expression ofnifBgene fromHerbaspirillum seropedicaeis dependent upon the NifA and RpoN proteins. Can J Microbiol 2006; 52:1199-207. [PMID: 17473889 DOI: 10.1139/w06-085] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [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: 11/22/2022]
Abstract
The putative nifB promoter region of Herbaspirillum seropedicae contained two sequences homologous to NifA-binding site and a –24/–12 type promoter. A nifB::lacZ fusion was assayed in the backgrounds of both Escherichia coli and H. seropedicae. In E. coli, the expression of nifB::lacZ occurred only in the presence of functional rpoN and Klebsiella pneumoniae nifA genes. In addition, the integration host factor (IHF) stimulated the expression of the nifB::lacZ fusion in this background. In H. seropedicae, nifB expression occurred only in the absence of ammonium and under low levels of oxygen, and it was shown to be strictly dependent on NifA. DNA band shift experiments showed that purified K. pneumoniae RpoN and E. coli IHF proteins were capable of binding to the nifB promoter region, and in vivo dimethylsulfate footprinting showed that NifA binds to both NifA-binding sites. These results strongly suggest that the expression of the nifB promoter of H. seropedicae is dependent on the NifA and RpoN proteins and that the IHF protein stimulates NifA activation of nifB promoter.Key words: Herbaspirillum seropedicae, nif, nitrogen fixation, NifA, RpoN.
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Affiliation(s)
- Fabiane G M Rego
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Paraná, Curitiba, PR, Brazil
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35
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Kuznetsov SV, Sugimura S, Vivas P, Crothers DM, Ansari A. Direct observation of DNA bending/unbending kinetics in complex with DNA-bending protein IHF. Proc Natl Acad Sci U S A 2006; 103:18515-20. [PMID: 17124171 PMCID: PMC1656971 DOI: 10.1073/pnas.0608394103] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [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: 11/18/2022] Open
Abstract
Regulation of gene expression involves formation of specific protein-DNA complexes in which the DNA is often bent or sharply kinked. Kinetics measurements of DNA bending when in complex with the protein are essential for understanding the molecular mechanism that leads to precise recognition of specific DNA-binding sites. Previous kinetics measurements on several DNA-bending proteins used stopped-flow techniques that have limited time resolution of few milliseconds. Here we use a nanosecond laser temperature-jump apparatus to probe, with submillisecond time resolution, the kinetics of bending/unbending of a DNA substrate bound to integration host factor (IHF), an architectural protein from Escherichia coli. The kinetics are monitored with time-resolved FRET, with the DNA substrates end-labeled with a FRET pair. The temperature-jump measurements, in combination with stopped-flow measurements, demonstrate that the binding of IHF to its cognate DNA site involves an intermediate state with straight or, possibly, partially bent DNA. The DNA bending rates range from approximately 2 ms(-1) at approximately 37 degrees C to approximately 40 ms(-1) at approximately 10 degrees C and correspond to an activation energy of approximately 14 +/- 3 kcal/mol. These rates and activation energy are similar to those of a single A:T base pair opening inside duplex DNA. Thus, our results suggest that spontaneous thermal disruption in base-paring, nucleated at an A:T site, may be sufficient to overcome the free energy barrier needed to partially bend/kink DNA before forming a tight complex with IHF.
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Affiliation(s)
| | - Sawako Sugimura
- Department of Chemistry, Yale University, P.O. Box 208107, New Haven, CT 06520
| | | | - Donald M. Crothers
- Department of Chemistry, Yale University, P.O. Box 208107, New Haven, CT 06520
- To whom correspondence may be addressed. E-mail:
or
| | - Anjum Ansari
- Departments of *Physics (M/C 273) and
- Bioengineering (M/C 063), University of Illinois, 845 West Taylor Street, Chicago, IL 60607; and
- To whom correspondence may be addressed. E-mail:
or
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36
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Abstract
Integration host factor (IHF) is a prokaryotic protein required for the integration of lambda phage DNA into its host genome. An x-ray crystal structure of the complex shows that IHF binds to the minor groove of DNA and bends the double helix by 160 degrees [Rice PA, Yang S, Mizuuchi K, Nash HA (1996) Cell 87:1295-1306]. We sought to dissect the complex formation process into its component binding and bending reaction steps, using stopped-flow fluorimetry to observe changes in resonance energy transfer between DNA-bound dyes, which in turn reflect distance changes upon bending. Different DNA substrates that are likely to increase or decrease the DNA bending rate were studied, including one with a nick in a critical kink position, and a substrate with longer DNA ends to increase hydrodynamic friction during bending. Kinetic experiments were carried out under pseudofirst-order conditions, in which the protein concentration is in substantial excess over DNA. At lower concentrations, the reaction rate rises linearly with protein concentration, implying rate limitation by the bimolecular reaction step. At high concentrations the rate reaches a plateau value, which strongly depends on temperature and the nature of the DNA substrate. We ascribe this reaction limit to the DNA bending rate and propose that complex formation is sequential at high concentration: IHF binds rapidly to DNA, followed by slower DNA bending. Our observations on the bending step kinetics are in agreement with results using the temperature-jump kinetic method.
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Affiliation(s)
- Sawako Sugimura
- Department of Chemistry, Yale University, P.O. Box 208107, New Haven, CT 06520
| | - Donald M. Crothers
- Department of Chemistry, Yale University, P.O. Box 208107, New Haven, CT 06520
- To whom correspondence should be addressed. E-mail:
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37
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Aeling KA, Opel ML, Steffen NR, Tretyachenko-Ladokhina V, Hatfield GW, Lathrop RH, Senear DF. Indirect recognition in sequence-specific DNA binding by Escherichia coli integration host factor: the role of DNA deformation energy. J Biol Chem 2006; 281:39236-48. [PMID: 17035240 DOI: 10.1074/jbc.m606363200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [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: 11/06/2022] Open
Abstract
Integration host factor (IHF) is a bacterial histone-like protein whose primary biological role is to condense the bacterial nucleoid and to constrain DNA supercoils. It does so by binding in a sequence-independent manner throughout the genome. However, unlike other structurally related bacterial histone-like proteins, IHF has evolved a sequence-dependent, high affinity DNA-binding motif. The high affinity binding sites are important for the regulation of a wide range of cellular processes. A remarkable feature of IHF is that it employs an indirect readout mechanism to bind and wrap DNA at both the nonspecific and high affinity (sequence-dependent) DNA sites. In this study we assessed the contributions of pre-formed and protein-induced DNA conformations to the energetics of IHF binding. Binding energies determined experimentally were compared with energies predicted for the IHF-induced deformation of the DNA helix (DNA deformation energy) in the IHF-DNA complex. Combinatorial sets of de novo DNA sequences were designed to systematically evaluate the influence of sequence-dependent structural characteristics of the conserved IHF recognition elements of the consensus DNA sequence. We show that IHF recognizes pre-formed conformational characteristics of the consensus DNA sequence at high affinity sites, whereas at all other sites relative affinity is determined by the deformational energy required for nearest-neighbor base pairs to adopt the DNA structure of the bound DNA-IHF complex.
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Affiliation(s)
- Kimberly A Aeling
- Institute for Genomics and Bioinformatics, Department of Microbiology and Molecular Genetics, School of Medicine, University of California 92697, USA
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38
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Abstract
The requirement for host factors in the transmission of integrative and conjugative elements (ICEs) has not been extensively explored. Here we tested whether integration host factor (IHF) or Fis, two host-encoded nucleoid proteins, are required for transfer of SXT, a Vibrio cholerae-derived ICE that can be transmitted to many gram-negative species. Fis did not influence the transfer of SXT to or from V. cholerae. In contrast, IHF proved to be required for V. cholerae to act as an SXT donor. In the absence of IHF, V. cholerae displayed a modest defect for serving as an SXT recipient. Surprisingly, SXT integration into or excision from the V. cholerae chromosome, which requires an SXT-encoded integrase related to lambda integrase, did not require IHF. Therefore, the defect in SXT transmission in the V. cholerae IHF mutant is probably not related to IHF's ability to promote DNA recombination. The V. cholerae IHF mutant was also highly impaired as a donor of RP4, a broad-host-range conjugative plasmid. Thus, the V. cholerae IHF mutant appears to have a general defect in conjugation. Escherichia coli IHF mutants were not impaired as donors or recipients of SXT or RP4, indicating that IHF is a V. cholerae-specific conjugation factor.
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Affiliation(s)
- Sarah M McLeod
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Howard Hughes Medical Institute, 136 Harrison Avenue, Boston, MA 02111, USA
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39
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Abstract
The Escherichia coli chromosome is condensed into an ill-defined structure known as the nucleoid. Nucleoid-associated DNA-binding proteins are involved in maintaining this structure and in mediating chromosome compaction. We have exploited chromatin immunoprecipitation and high-density microarrays to study the binding of three such proteins, FIS, H-NS and IHF, across the E.coli genome in vivo. Our results show that the distribution of these proteins is biased to intergenic parts of the genome, and that the binding profiles overlap. Hence some targets are associated with combinations of bound FIS, H-NS and IHF. In addition, many regions associated with FIS and H-NS are also associated with RNA polymerase.
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Affiliation(s)
- David C. Grainger
- To whom correspondence should be addressed. Tel: +44 121 414 5435; Fax: +44 121 414 5925;
| | - Douglas Hurd
- Oxford Gene Technology, Begbroke Science ParkSandy Lane, Yarnton, Oxford OX5 1PF, UK
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40
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Gerstel U, Kolb A, Römling U. Regulatory components at the csgD promoter--additional roles for OmpR and integration host factor and role of the 5' untranslated region. FEMS Microbiol Lett 2006; 261:109-17. [PMID: 16842367 DOI: 10.1111/j.1574-6968.2006.00332.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [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: 11/30/2022] Open
Abstract
CsgD is a master regulator of multicellular behaviour in Salmonella enterica serovar Typhimurium. Expression of CsgD is highly regulated on the transcriptional level. A nucleo-protein complex had been defined where the global regulators OmpR and integration host factor (IHF) bind up- and downstream of the csgD core promoter. In this study, the nucleo-protein complex of PcsgD was extended through characterization of additional OmpR and IHF binding sites that influence the transcriptional activity of the csgD promoter. Furthermore, the role of the 174 bp long 5'-untranslated region on transcriptional activity was defined.
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Affiliation(s)
- Ulrich Gerstel
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden
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41
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Browning DF, Lee DJ, Wolfe AJ, Cole JA, Busby SJW. The Escherichia coli K-12 NarL and NarP proteins insulate the nrf promoter from the effects of integration host factor. J Bacteriol 2006; 188:7449-56. [PMID: 16936015 PMCID: PMC1636288 DOI: 10.1128/jb.00975-06] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [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
The Escherichia coli K-12 nrf operon promoter can be activated fully by the FNR protein (regulator of fumarate and nitrate reduction) binding to a site centered at position -41.5. FNR-dependent transcription is suppressed by integration host factor (IHF) binding at position -54, and this suppression is counteracted by binding of the NarL or NarP response regulator at position -74.5. The E. coli acs gene is transcribed from a divergent promoter upstream from the nrf operon promoter. Transcription from the major acsP2 promoter is dependent on the cyclic AMP receptor protein and is modulated by IHF and Fis binding at multiple sites. We show that IHF binding to one of these sites, located at position -127 with respect to the nrf promoter, has a positive effect on nrf promoter activity. This activation is dependent on the face of the DNA helix, independent of IHF binding at other locations, and found only when NarL/NarP are not bound at position -74.5. Binding of NarL/NarP appears to insulate the nrf promoter from the effects of IHF. The acs-nrf regulatory region is conserved in other pathogenic E. coli strains and related enteric bacteria but differs in Salmonella enterica serovar Typhimurium.
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Affiliation(s)
- Douglas F Browning
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom.
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42
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43
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Abstract
The farAB operon encodes an efflux pump system that mediates the resistance of Neisseria gonorrhoeae to antimicrobial long-chain fatty acids. We previously observed that expression of farAB is negatively regulated by the FarR repressor. In this study, we examined the molecular mechanism by which FarR represses expression of farAB. DNase I footprinting analysis, coupled with a deletion analysis of the farAB promoter region, indicated that FarR binds to three sites (termed sites A, B and C) within the DNA sequence upstream of farA; genetic analysis revealed, however, that site B is not required for FarR repression of farAB. This repression also required the presence of Integration Host Factor (IHF), which was found to bind to sequences located between FarR binding sites A and C. We determined that IHF binding to the farAB promoter region could inhibit transcription in vitro and that such binding induced a bending of the target DNA, which we propose to be important in regulating this operon. IHF binding to the promoter region was found to stabilize the binding of FarR to its binding sites A and C and as a consequence, enhanced repression of farAB expression mediated by FarR. We propose a model in which expression of the farAB-encoded efflux pump in N. gonorrhoeae is modulated by the DNA binding activities of FarR and IHF.
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Affiliation(s)
- Eun-Hee Lee
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA 30322, USA
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44
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Ortega ME, Catalano CE. Bacteriophage lambda gpNu1 and Escherichia coli IHF proteins cooperatively bind and bend viral DNA: implications for the assembly of a genome-packaging motor. Biochemistry 2006; 45:5180-9. [PMID: 16618107 DOI: 10.1021/bi052284b] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [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: 11/29/2022]
Abstract
Terminase enzymes are common to both prokaryotic and eukaryotic double-stranded DNA viruses and are responsible for packaging viral DNA into the confines of an empty procapsid shell. In all known cases, the holoenzymes are heteroligomers composed of a large subunit that possesses the catalytic activities required for genome packaging and a small subunit that is responsible for specific recognition of viral DNA. In bacteriophage lambda, the DNA recognition protein is gpNu1. The gpNu1 subunit interacts with multiple recognition elements within cos, the packaging initiation site in viral DNA, to site-specifically assemble the packaging machinery. Motor assembly is modulated by the Escherichia coli integration host factor protein (IHF), which binds to a consensus sequence also located within cos. On the basis of a variety of biochemical data and the recently solved NMR structure of the DNA binding domain of gpNu1, we proposed a novel DNA binding mode that predicts significant bending of duplex DNA by gpNu1 (de Beer et al. (2002) Mol. Cell 9, 981-991). We further proposed that gpNu1 and IHF cooperatively bind and bend viral DNA to regulate the assembly of the packaging motor. Here, we characterize cooperative gpNu1 and IHF binding to the cos site in lambda DNA using a quantitative electrophoretic mobility shift (EMS) assay. These studies provide direct experimental support for the long presumed cooperative assembly of gpNu1 and IHF at the cos sequence of lambda DNA. Further, circular permutation experiments demonstrate that the viral and host proteins each introduce a strong bend in cos-containing DNA, but not nonspecific DNA substrates. Thus, specific recognition of viral DNA by the packaging apparatus is mediated by both DNA sequence information and by structural alteration of the duplex. The relevance of these results with respect to the assembly of a viral DNA-packaging motor is discussed.
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Affiliation(s)
- Marcos E Ortega
- Department of Biochemistry and Molecular Genetics, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA
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45
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Abstract
In Escherichia coli, Fe-S clusters are assembled by gene products encoded from the isc and suf operons. Both the iscRSUA and sufABCDSE operons are induced highly by oxidants, reflecting an increased need for providing and maintaining Fe-S clusters under oxidative stress conditions. Three cis-acting oxidant-responsive elements (ORE-I, II, III) in the upstream of the sufA promoter serve as the binding sites for OxyR, IHF and an uncharacterized factor respectively. Using DNA affinity fractionation, we isolated an ORE-III-binding factor that positively regulates the suf operon in response to various oxidants. MALDI-TOF mass analysis identified it with IscR, known to serve as a repressor of the iscRSUA gene expression under anaerobic condition as a [2Fe-2S]-bound form. The iscR null mutation abolished ORE-III-binding activity in cell extracts, and caused a significant decrease in the oxidant induction of sufA in vivo. OxyR and IscR contributed almost equally to activate the sufA operon in response to oxidants. Purified IscR that lacked Fe-S cluster bound to the ORE-III site and activated transcription from the sufA promoter in vitro. Mutations in Fe-S-binding sites of IscR enabled sufA activation in vivo and in vitro. These results support a model that IscR in its demetallated form directly activates sufA transcription, while it de-represses isc operon, under oxidative stress condition.
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Affiliation(s)
- Won-Sik Yeo
- Laboratory of Molecular Microbiology, School of Biological Sciences, and, Institute of Microbiology, Seoul National University, Seoul 151-742, Korea
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46
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Devroede N, Huysveld N, Charlier D. Mutational analysis of intervening sequences connecting the binding sites for integration host factor, PepA, PurR, and RNA polymerase in the control region of the Escherichia coli carAB operon, encoding carbamoylphosphate synthase. J Bacteriol 2006; 188:3236-45. [PMID: 16621816 PMCID: PMC1447446 DOI: 10.1128/jb.188.9.3236-3245.2006] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2005] [Accepted: 02/20/2006] [Indexed: 11/20/2022] Open
Abstract
Transcription of the carAB operon encoding the unique carbamoylphosphate synthase of Escherichia coli reflects the dual function of carbamoylphosphate in the biosynthesis of arginine and pyrimidine nucleotides. The tandem pair of promoters is regulated by various mechanisms depending on the needs of both pathways and the maintenance of a pyrimidine/purine nucleotide balance. Here we focus on the linker regions that impose the distribution of target sites for DNA-binding proteins involved in pyrimidine- and purine-specific repression of the upstream promoter P1. We introduced deletions and insertions, and combinations thereof, in four linkers connecting the binding sites for integration host factor (IHF), PepA, PurR, and RNA polymerase and studied the importance of phasing and spacing of the targets and the importance of the nucleotide sequence of the linkers. The two PepA binding sites must be properly aligned and separated with respect to each other and to the promoter for both pyrimidine- and purine-mediated repression. Similarly, the phasing and spacing of the IHF and PEPA2 sites are strictly constrained but only for pyrimidine-specific repression. The IHF target is even dispensable for purine-mediated regulation. Thus, a correct localization of PepA within the higher-order nucleoprotein complex is a prerequisite for the establishment of pyrimidine-mediated repression and for the coupling between purine- and pyrimidine-dependent regulation. Our data also suggest the existence of a novel cis-acting pyrimidine-specific regulatory target located around position -60. Finally, the analysis of a P1 derivative devoid of its control region has led to a reappraisal of the effect of excess adenine on P1 and has revealed that P1 has no need for a UP element.
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Affiliation(s)
- Neel Devroede
- Erfelijkheidsleer en Microbiologie (MICR), Pleinlaan 2, B-1050 Brussels, Belgium
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47
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Taschner NP, Yagil E, Spira B. The effect of IHF on sigmaS selectivity of the phoA and pst promoters of Escherichia coli. Arch Microbiol 2006; 185:234-7. [PMID: 16404567 DOI: 10.1007/s00203-005-0082-4] [Citation(s) in RCA: 14] [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] [Subscribe] [Scholar Register] [Received: 08/23/2005] [Revised: 12/13/2005] [Accepted: 12/20/2005] [Indexed: 11/29/2022]
Abstract
The pst operon, a member of the PHO regulon of Escherichia coli, encodes a high-affinity phosphate transport system whose expression is induced when the cells enter a phase of phosphate starvation. The expression of pst is stimulated by the integration host factor (IHF). Transcription of the PHO regulon genes is initiated by the RNA polymerase complexed with sigma (D) (Esigma (D)). Owing to a cytosine residue at position -13 of the pst promoter its transcription can also be initiated by Esigma (S). Here, we show that inactivation of IHF in vivo abolishes the sigma (S)-dependent transcription initiation of the pst operon, indicating that both -13C residue and IHF are required to confer on pst the ability to be transcribed by Esigma (S). Introduction of a -13C residue in the promoter region of phoA, another PHO regulon gene that is not directly affected by IHF, did not affect its exclusive transcription initiation by Esigma (D).
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Affiliation(s)
- Natalia Pasternak Taschner
- Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, Av. Prof. Lineu Prestes 1374, CEP 05508-900, São Paulo, Brazil
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48
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Browning DF, Grainger DC, Beatty CM, Wolfe AJ, Cole JA, Busby SJW. Integration of three signals at the Escherichia coli nrf promoter: a role for Fis protein in catabolite repression. Mol Microbiol 2005; 57:496-510. [PMID: 15978080 DOI: 10.1111/j.1365-2958.2005.04701.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [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: 11/28/2022]
Abstract
Expression from the Escherichia coli nrf operon promoter is activated by the anaerobically triggered transcription factor, FNR, and by the nitrate/nitrite ion-controlled response regulators, NarL or NarP, but is repressed by the IHF and Fis proteins. Here, we present in vitro studies on the nrf promoter, using permanganate footprinting to measure open complex formation, and DNase I footprinting to monitor binding of the different regulators and the interactions between them. Our results show that open complex formation is completely dependent on FNR and is enhanced by NarL, but is repressed by IHF or Fis. NarL counteracts repression by IHF but is unable to alter repression by Fis. These results suggest mechanisms by which nrf promoter activity is modulated by the different factors. Expression from the nrf promoter is known to be repressed in rich media, especially in the presence of glucose, but the molecular basis of this is not understood. Here, we show that this catabolite repression is relieved by mutations that weaken the DNA site for Fis, improve the DNA site for FNR or improve the promoter -10 or -35 elements. Hence, Fis protein is a major factor responsible for catabolite repression at the nrf promoter, and Fis can override activation by FNR and NarL or NarP.
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Affiliation(s)
- Douglas F Browning
- School of Biosciences, The University of Birmingham, Birmingham B15 2TT, UK
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49
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Abstract
In Pseudomonas fluorescens ST, the promoter of the styrene catabolic operon, PstyA, is induced by styrene and repressed by the addition of preferred carbon sources. PstyA is regulated by the StyS/StyR two-component system. The integration host factor (IHF) also plays a positive role in PstyA regulation. Three distinct StyR binding sites, which have different affinities for this response regulator, have been characterized on PstyA. The high-affinity StyR binding site (STY2) is necessary for promoter activity. The DNA region upstream of STY2 contains a lower-affinity StyR binding site, STY1, that partially overlaps the IHF binding site. Deletion of this region, designated URE (upstream regulatory element), has a dual effect on the PstyA promoter, decreasing the styrene-dependent activity and partially relieving the glucose repression. The lowest-affinity StyR binding site (STY3) is located downstream of the transcription start point. Deletion of the URE region and inactivation of the STY3 site completely abolished glucose-mediated repression of PstyA. In the proposed model StyR can act either as an activator or as a repressor, depending on which sites it occupies in the different growth conditions. We suggest that the cellular levels of phosphorylated StyR, as determined by StyS sensor kinase activity, and the interplay of this molecule with IHF modulate the activity of the promoter in different growth conditions.
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Affiliation(s)
- Livia Leoni
- Department of Biology, University Roma Tre, Viale G. Marconi 446, 00146 Rome, Italy
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50
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Abstract
The histone-like nucleoid structuring (H-NS) protein is a global transcriptional regulator that is known to regulate stress response pathways and virulence genes in bacteria. It has also been implicated in the regulation of bacterial transposition systems, including Tn10. We demonstrate here that H-NS promotes Tn10 transposition by binding directly to the transposition complex (or transpososome). We present evidence that, upon binding, H-NS induces the unfolding of the Tn10 transpososome and helps to maintain the transpososome in an unfolded state. This ensures that intermolecular (as opposed to self-destructive intramolecular) transposition events are favored. We present evidence that H-NS binding to the flanking donor DNA of the transpososome is the initiating event in the unfolding process. We propose that by recruiting H-NS as a modulator of transposition, Tn10 has evolved a means of sensing changes in host physiology, as the amount of H-NS in the cell, as well its activity, are responsive to changes in environmental conditions. Sensing of environmental changes through H-NS would allow transposition to occur when it is most opportune for both the transposon and the host.
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Affiliation(s)
- Simon J Wardle
- Department of Biochemistry, University of Western Ontario, London, Ontario N6A 5C1 Canada
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