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Muskhelishvili G, Sobetzko P, Travers A. Spatiotemporal Coupling of DNA Supercoiling and Genomic Sequence Organization-A Timing Chain for the Bacterial Growth Cycle? Biomolecules 2022; 12:biom12060831. [PMID: 35740956 PMCID: PMC9221221 DOI: 10.3390/biom12060831] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 06/08/2022] [Accepted: 06/08/2022] [Indexed: 01/25/2023] Open
Abstract
In this article we describe the bacterial growth cycle as a closed, self-reproducing, or autopoietic circuit, reestablishing the physiological state of stationary cells initially inoculated in the growth medium. In batch culture, this process of self-reproduction is associated with the gradual decline in available metabolic energy and corresponding change in the physiological state of the population as a function of "travelled distance" along the autopoietic path. We argue that this directional alteration of cell physiology is both reflected in and supported by sequential gene expression along the chromosomal OriC-Ter axis. We propose that during the E. coli growth cycle, the spatiotemporal order of gene expression is established by coupling the temporal gradient of supercoiling energy to the spatial gradient of DNA thermodynamic stability along the chromosomal OriC-Ter axis.
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Affiliation(s)
- Georgi Muskhelishvili
- School of Natural Sciences, Biology Program, Agricultural University of Georgia, 0159 Tbilisi, Georgia
- Correspondence:
| | - Patrick Sobetzko
- Synmikro, Loewe Center for Synthetic Microbiology, Philipps-Universität Marburg, 35043 Marburg, Germany;
| | - Andrew Travers
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK;
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2
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Watson GD, Chan EW, Leake MC, Noy A. Structural interplay between DNA-shape protein recognition and supercoiling: The case of IHF. Comput Struct Biotechnol J 2022; 20:5264-5274. [PMID: 36212531 PMCID: PMC9519438 DOI: 10.1016/j.csbj.2022.09.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 09/12/2022] [Accepted: 09/12/2022] [Indexed: 11/03/2022] Open
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3
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Higgins NP, Vologodskii AV. Topological Behavior of Plasmid DNA. Microbiol Spectr 2015; 3:10.1128/microbiolspec.PLAS-0036-2014. [PMID: 26104708 PMCID: PMC4480603 DOI: 10.1128/microbiolspec.plas-0036-2014] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Indexed: 11/20/2022] Open
Abstract
The discovery of the B-form structure of DNA by Watson and Crick led to an explosion of research on nucleic acids in the fields of biochemistry, biophysics, and genetics. Powerful techniques were developed to reveal a myriad of different structural conformations that change B-DNA as it is transcribed, replicated, and recombined and as sister chromosomes are moved into new daughter cell compartments during cell division. This article links the original discoveries of superhelical structure and molecular topology to non-B form DNA structure and contemporary biochemical and biophysical techniques. The emphasis is on the power of plasmids for studying DNA structure and function. The conditions that trigger the formation of alternative DNA structures such as left-handed Z-DNA, inter- and intra-molecular triplexes, triple-stranded DNA, and linked catenanes and hemicatenanes are explained. The DNA dynamics and topological issues are detailed for stalled replication forks and for torsional and structural changes on DNA in front of and behind a transcription complex and a replisome. The complex and interconnected roles of topoisomerases and abundant small nucleoid association proteins are explained. And methods are described for comparing in vivo and in vitro reactions to probe and understand the temporal pathways of DNA and chromosome chemistry that occur inside living cells.
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Affiliation(s)
- N Patrick Higgins
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL 35294
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4
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Choi W, Saha RP, Jang S, Harshey RM. Controlling DNA degradation from a distance: a new role for the Mu transposition enhancer. Mol Microbiol 2014; 94:595-608. [PMID: 25256747 DOI: 10.1111/mmi.12781] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/29/2014] [Indexed: 11/30/2022]
Abstract
Phage Mu is unique among transposable elements in employing a transposition enhancer. The enhancer DNA segment is the site where the transposase MuA binds and makes bridging interactions with the two Mu ends, interwrapping the ends with the enhancer in a complex topology essential for assembling a catalytically active transpososome. The enhancer is also the site at which regulatory proteins control divergent transcription of genes that determine the phage lysis-lysogeny decision. Here we report a third function for the enhancer - that of regulating degradation of extraneous DNA attached to both ends of infecting Mu. This DNA is protected from nucleases by a phage protein until Mu integrates into the host chromosome, after which it is rapidly degraded. We find that leftward transcription at the enhancer, expected to disrupt its topology within the transpososome, blocks degradation of this DNA. Disruption of the enhancer would lead to the loss or dislocation of two non-catalytic MuA subunits positioned in the transpososome by the enhancer. We provide several lines of support for this inference, and conclude that these subunits are important for activating degradation of the flanking DNA. This work also reveals a role for enhancer topology in phage development.
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Affiliation(s)
- Wonyoung Choi
- Department of Molecular Biosciences & Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, TX, 78712, USA
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5
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Saha RP, Lou Z, Meng L, Harshey RM. Transposable prophage Mu is organized as a stable chromosomal domain of E. coli. PLoS Genet 2013; 9:e1003902. [PMID: 24244182 PMCID: PMC3820752 DOI: 10.1371/journal.pgen.1003902] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2013] [Accepted: 09/06/2013] [Indexed: 11/19/2022] Open
Abstract
The E. coli chromosome is compacted by segregation into 400–500 supercoiled domains by both active and passive mechanisms, for example, transcription and DNA-protein association. We find that prophage Mu is organized as a stable domain bounded by the proximal location of Mu termini L and R, which are 37 kbp apart on the Mu genome. Formation/maintenance of the Mu ‘domain’ configuration, reported by Cre-loxP recombination and 3C (chromosome conformation capture), is dependent on a strong gyrase site (SGS) at the center of Mu, the Mu L end and MuB protein, and the E. coli nucleoid proteins IHF, Fis and HU. The Mu domain was observed at two different chromosomal locations tested. By contrast, prophage λ does not form an independent domain. The establishment/maintenance of the Mu domain was promoted by low-level transcription from two phage promoters, one of which was domain dependent. We propose that the domain confers transposition readiness to Mu by fostering topological requirements of the reaction and the proximity of Mu ends. The potential benefits to the host cell from a subset of proteins expressed by the prophage may in turn help its long-term stability. A majority of sequenced bacterial genomes harbor prophage sequences. Some prophages are viable, while others have decayed from accumulating mutations and genome rearrangements. Prophages, including defective ones, can contribute important biological properties such as antibiotic resistance, toxins, and serum resistance that increase the survival and ecological range of their hosts. We show in this study that the 37 kbp transposable prophage Mu exists in a unique configuration we call the ‘Mu domain’, where its two ends are paired, segregating the Mu sequences from those of the host chromosome. This is the largest stable chromosomal domain in E. coli mapped to date. The Mu domain configuration promotes low-level transcription from an early prophage promoter, which controls the expression of several genes, not all essential for phage growth. Some non-essential genes include DNA repair functions. We suggest that the Mu domain provides long-term survival benefits to both the prophage and the host: to the prophage in bestowing transposition-ready topological properties unique to the Mu reaction, and to the host in contributing extraneous DNA housekeeping functions.
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Affiliation(s)
- Rudra P. Saha
- Department of Molecular Biosciences & Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas, United States of America
| | - Zheng Lou
- Department of Molecular Biosciences & Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas, United States of America
| | - Luke Meng
- Department of Molecular Biosciences & Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas, United States of America
| | - Rasika M. Harshey
- Department of Molecular Biosciences & Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas, United States of America
- * E-mail:
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6
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Jang S, Sandler SJ, Harshey RM. Mu insertions are repaired by the double-strand break repair pathway of Escherichia coli. PLoS Genet 2012; 8:e1002642. [PMID: 22511883 PMCID: PMC3325207 DOI: 10.1371/journal.pgen.1002642] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Accepted: 02/22/2012] [Indexed: 11/21/2022] Open
Abstract
Mu is both a transposable element and a temperate bacteriophage. During lytic growth, it amplifies its genome by replicative transposition. During infection, it integrates into the Escherichia coli chromosome through a mechanism not requiring extensive DNA replication. In the latter pathway, the transposition intermediate is repaired by transposase-mediated resecting of the 5′ flaps attached to the ends of the incoming Mu genome, followed by filling the remaining 5 bp gaps at each end of the Mu insertion. It is widely assumed that the gaps are repaired by a gap-filling host polymerase. Using the E. coli Keio Collection to screen for mutants defective in recovery of stable Mu insertions, we show in this study that the gaps are repaired by the machinery responsible for the repair of double-strand breaks in E. coli—the replication restart proteins PriA-DnaT and homologous recombination proteins RecABC. We discuss alternate models for recombinational repair of the Mu gaps. Transposon activity shapes genome structure and evolution. The movement of these elements generates target site duplications as a result of staggered cuts in the target made initially by the transposase. For replicative transposons, the single-stranded gaps generated after the initial strand transfer event are filled by target-primed replication. However, the majority of known transposable elements transpose by a non-replicative mechanism. Despite a wealth of information available for the mechanism of transposase action, little is known about how the cell repairs gaps left in the wake of transposition of these majority elements. Phage Mu is unique in using both replicative and non-replicative modes of transposition. Our study finds that during its non-replicative pathway, the gaps created by Mu insertion are repaired by the primary machinery for double-strand break repair in E. coli, not by gap-filling polymerases as previously thought. This first report of specific host processes involved in repair of transposon insertions in bacteria is likely to have a broad significance, given also that double-strand break repair pathways have been implicated in repair of the retroviral and Line retroelement insertions.
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Affiliation(s)
- Sooin Jang
- Section of Molecular Genetics and Microbiology and Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas, United States of America
| | - Steven J. Sandler
- Department of Microbiology, Morill Science Center, University of Massachusetts at Amherst, Amherst, Massachusetts, United States of America
| | - Rasika M. Harshey
- Section of Molecular Genetics and Microbiology and Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas, United States of America
- * E-mail:
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7
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Champion K, Higgins NP. Growth rate toxicity phenotypes and homeostatic supercoil control differentiate Escherichia coli from Salmonella enterica serovar Typhimurium. J Bacteriol 2007; 189:5839-49. [PMID: 17400739 PMCID: PMC1952050 DOI: 10.1128/jb.00083-07] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Escherichia coli and Salmonella enterica serovar Typhimurium share high degrees of DNA and amino acid identity for 65% of the homologous genes shared by the two genomes. Yet, there are different phenotypes for null mutants in several genes that contribute to DNA condensation and nucleoid formation. The mutant R436-S form of the GyrB protein has a temperature-sensitive phenotype in Salmonella, showing disruption of supercoiling near the terminus and replicon failure at 42 degrees C. But this mutation in E. coli is lethal at the permissive temperature. A unifying hypothesis for why the same mutation in highly conserved homologous genes of different species leads to different physiologies focuses on homeotic supercoil control. During rapid growth in mid-log phase, E. coli generates 15% more negative supercoils in pBR322 DNA than Salmonella. Differences in compaction and torsional strain on chromosomal DNA explain a complex set of single-gene phenotypes and provide insight into how supercoiling may modulate epigenetic effects on chromosome structure and function and on prophage behavior in vivo.
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Affiliation(s)
- Keith Champion
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama 35294-0024
| | - N. Patrick Higgins
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama 35294-0024
- Corresponding author. Mailing address: KAUL-524, 720 20th Street South, Birmingham, AL 35294. Phone: (205) 934-3299. Fax: (205) 975-5955. E-mail:
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8
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Abstract
DNA transposition is central to the propagation of temperate phage Mu. A long-standing problem in Mu biology has been the mechanism by which the linear genome of an infecting phage, which is linked at both ends to DNA acquired from a previous host, integrates into the new host chromosome. If Mu were to use its well-established cointegrate mechanism for integration (single-strand nicks at Mu ends, joined to a staggered double-strand break in the target), the flanking host sequences would remain linked to Mu; target-primed replication of the linear integrant would subsequently break the chromosome. The absence of evidence for chromosome breaks has led to speculation that infecting Mu might use a cut-and-paste mechanism, whereby Mu DNA is cut away from the flanking sequences prior to integration. In this study we have followed the fate of the flanking DNA during the time course of Mu infection. We have found that these sequences are still attached to Mu upon integration and that they disappear soon after. The data rule out a cut-and-paste mechanism and suggest that infecting Mu integrates to generate simple insertions by a variation of its established cointegrate mechanism in which, instead of a "nick, join, and replicate" pathway, it follows a "nick, join, and process" pathway. The results show similarities with human immunodeficiency virus integration and provide a unifying mechanism for development of Mu along either the lysogenic or lytic pathway.
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Affiliation(s)
- T K Au
- Section of Molecular Genetics and Microbiology and Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA
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9
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Muir RE, Gober JW. Role of integration host factor in the transcriptional activation of flagellar gene expression in Caulobacter crescentus. J Bacteriol 2005; 187:949-60. [PMID: 15659673 PMCID: PMC545733 DOI: 10.1128/jb.187.3.949-960.2005] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In the Caulobacter crescentus predivisional cell, class III and IV flagellar genes, encoding the extracytoplasmic components of the flagellum, are transcribed in the nascent swarmer compartment. This asymmetric expression pattern is attributable to the compartmentalized activity of the sigma54-dependent transcriptional activator FlbD. Additionally, these temporally transcribed flagellar promoters possess a consensus sequence for the DNA-binding protein integration host factor (IHF), located between the upstream FlbD binding site and the promoter sequences. Here, we deleted the C. crescentus gene encoding the beta-subunit of the IHF, ihfB (himD), and examined the effect on flagellar gene expression. The DeltaihfB strain exhibited a mild defect in cell morphology and impaired motility. Using flagellar promoter reporter fusions, we observed that expression levels of a subset of class III flagellar promoters were decreased by the loss of IHF. However, one of these promoters, fliK-lacZ, exhibited a wild-type cell cycle-regulated pattern of expression in the absence of IHF. Thus, IHF is required for maximal transcription of several late flagellar genes. The DeltaihfB strain was found to express significantly reduced amounts of the class IV flagellin, FljL, as a consequence of reduced transcriptional activity. Our results indicate that the motility defect exhibited by the DeltaihfB strain is most likely attributable to its failure to accumulate the class IV-encoded 27-kDa flagellin subunit, FljL.
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Affiliation(s)
- Rachel E Muir
- Department of Chemistry and Biochemistry and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095-1569, USA
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10
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Yin Z, Jayaram M, Pathania S, Harshey RM. The Mu Transposase Interwraps Distant DNA Sites within a Functional Transpososome in the Absence of DNA Supercoiling. J Biol Chem 2005; 280:6149-56. [PMID: 15563455 DOI: 10.1074/jbc.m411679200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A Mu transpososome assembled on negatively supercoiled DNA traps five supercoils by intertwining the left (L) and right (R) ends of Mu with an enhancer element (E). To investigate the contribution of DNA supercoiling to this elaborate synapse in which E and L cross once, E and R twice, and L and R twice, we have analyzed DNA crossings in a transpososome assembled on nicked substrates under conditions that bypass the supercoiling requirement for transposition. We find that the transposase MuA can recreate an essentially similar topology on nicked substrates, interwrapping both E-R and L-R twice but being unable to generate the single E-L crossing. In addition, we deduce that the functional MuA tetramer must contribute to three of the four observed crossings and, thus, to restraining the enhancer within the complex. We discuss the contribution of both MuA and DNA supercoiling to the 5-noded Mu synapse built at the 3-way junction.
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Affiliation(s)
- Zhiqi Yin
- Section of Molecular Genetics and Microbiology and Institute of Cellular and Molecular Biology, University of Texas, Austin, TX 78712, USA
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11
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Rousseau P, Laachouch JE, Chandler M, Toussaint A. Characterization of the cts4 repressor mutation in transposable bacteriophage Mu. Res Microbiol 2002; 153:511-8. [PMID: 12437212 DOI: 10.1016/s0923-2508(02)01363-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Mucts4 was isolated more than 30 years ago and was the first available thermoinducible derivative of transposable phage Mu. We have characterized the cts4 mutation and the corresponding mutant protein. Contrary to previously characterized thermoinducible Mu prophages (e.g., Mucts62), Mucts4 lysogenizes at reduced frequency even at 30 degrees C. The cts4 mutation (Leu129Val) was located in this central repressor region. The cts4 protein was thermosensitive for operator DNA binding in vitro. Temperature-dependent changes in protein-protein cross-linking patterns in the absence of DNA were detected for purified wild type, cts62 and cts4 repressor proteins. The cts4 protein exhibited a subtly different electrophoretic profile, which became more marked at higher temperatures, from both the wild type and cts62. In addition the cts4 repressor generated a significantly different pattern of binding to DNA fragments carrying the early operator region. Consistent with the predicted involvement of the central leucine-rich region of the Mu repressor in the formation of multimeric forms, the cts4 mutation thus appeared to affect protein-protein interactions.
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Affiliation(s)
- Philippe Rousseau
- Laboratoire de Microbiologie et de Génétique Moléculaire, CNRS-université Toulouse III, France
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12
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Kobryn K, Watson MA, Allison RG, Chaconas G. The Mu three-site synapse: a strained assembly platform in which delivery of the L1 transposase binding site triggers catalytic commitment. Mol Cell 2002; 10:659-69. [PMID: 12408832 DOI: 10.1016/s1097-2765(02)00596-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The Mu DNA transposition reaction proceeds through a three-site synaptic complex (LER), including the two Mu ends and the transpositional enhancer. We show that the LER contains highly stressed DNA regions in the enhancer and in the L1 transposase binding site. We propose that the L1 site acts as the keystone for assembly of a catalytically competent transpososome. Delivery of L1 through HU-mediated bending completes LER assembly, provides the trigger for necessary conformational transitions in transpososome formation, and allows target capture to occur. Relief of the stress at L1 and the enhancer may help drive Mu A tetramerization and engagement of the Mu ends by the transposase active site.
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Affiliation(s)
- Kerri Kobryn
- Department of Biochemistry, University of Western Ontario, London, Ontario, Canada
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13
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Dixon-Fyle SM, Caro L. Characterization in vitro and in vivo of a new HU family protein from Streptococcus thermophilus ST11. Plasmid 1999; 42:159-73. [PMID: 10545259 DOI: 10.1006/plas.1999.1423] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Streptococcus thermophilus is a thermophilic gram-positive bacterium belonging to the lactic acid group. We report the isolation and characterization of a new 9.6-kDa DNA-binding protein, HSth, belonging to the HU family of nucleoid-associated proteins. The hsth gene was isolated in a 2.5-kb genomic region, upstream of a gene with strong homology to Lactococcus lactis pyrD. It is transcribed from a single E. coli sigma(70)-like promoter. Based on its high level of sequence similarity to B. subtilis and E. coli HU, HSth appears to be an HU homologue. The HSth protein shows biochemical and functional properties typical of HU proteins from gram-positive bacteria, being heat-stable, acid-soluble, and homodimeric. When expressed in HU-deficient E. coli cells, HSth supported the growth of bacteriophage Mu as efficiently as E. coli HU homo- and heterodimeric proteins. It did not, however, display any IHF-specific functions. Finally, we show that HSth binds to linear DNA with no apparent specificity, forming protein-DNA complexes similar but not identical to those observed with E. coli HU proteins.
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Affiliation(s)
- S M Dixon-Fyle
- Department of Molecular Biology, University of Geneva, Geneva 4, 1211, Switzerland.
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14
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Narendja FM, Davis MA, Hynes MJ. AnCF, the CCAAT binding complex of Aspergillus nidulans, is essential for the formation of a DNase I-hypersensitive site in the 5' region of the amdS gene. Mol Cell Biol 1999; 19:6523-31. [PMID: 10490592 PMCID: PMC84622 DOI: 10.1128/mcb.19.10.6523] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The CCAAT sequence in the amdS promoter of Aspergillus nidulans is recognized by AnCF, a complex consisting of the three evolutionary conserved subunits HapB, HapC, and HapE. In this study we have investigated the effect of AnCF on the chromatin structure of the amdS gene. The AnCF complex and the CCAAT sequence were found to be necessary for the formation of a nucleosome-free, DNase I-hypersensitive region in the 5' region of the amdS gene. Deletion of the hapE gene results in loss of the DNase I-hypersensitive site, and the positioning of nucleosomes over the transcriptional start point is lost. Likewise, a point mutation in the CCAAT motif, as well as a 530-bp deletion which removes the CCAAT box, results in the loss of the DNase I-hypersensitive region. The DNase I-hypersensitive region and the nucleosome positioning can be restored by insertion of a 35-bp oligonucleotide carrying the CCAAT motif. A DNase I-hypersensitive region has been found in the CCAAT-containing fmdS gene and was also hapE dependent. These data indicate a critical role for the AnCF complex in establishing an open chromatin structure in A. nidulans.
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Affiliation(s)
- F M Narendja
- Department of Genetics, University of Melbourne, Parkville, Victoria 3052, Australia
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15
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Kobryn K, Lavoie BD, Chaconas G. Supercoiling-dependent site-specific binding of HU to naked Mu DNA. J Mol Biol 1999; 289:777-84. [PMID: 10369760 DOI: 10.1006/jmbi.1999.2805] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Using HU chemical nucleases to probe HU-DNA interactions, we report here for the first time site-specific binding of HU to naked DNA. An unique feature of this interaction is the absolute requirement for negative DNA supercoiling for detectable levels of site-specific DNA binding. The HU binding site is the Mu spacer between the L1 and L2 transposase binding sites. Our results suggest recognition of an altered DNA structure which is induced by DNA supercoiling. We propose that recruitment of HU to this naked DNA site induces the DNA bending required for productive synapsis and transpososome assembly. Implications of HU as a supercoiling sensor with a potential in vivo regulatory role are discussed. Finally, using HU nucleases we have also shown that non-specific DNA binding by HU is stimulated by increasing levels of supercoiling.
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Affiliation(s)
- K Kobryn
- Department of Biochemistry, University of Western Ontario, London, Ontario, N6A 5C1, Canada
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16
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17
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Senear DF, Ross JB, Laue TM. Analysis of protein and DNA-mediated contributions to cooperative assembly of protein-DNA complexes. Methods 1998; 16:3-20. [PMID: 9774512 DOI: 10.1006/meth.1998.0641] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The cooperative assembly of protein-DNA complexes is a widespread phenomenon that is of particular significance to transcriptional regulation. Assembly of these complexes is controlled by the chemistry of the macromolecular interactions. In this sense, transcriptional regulation is a chemical issue. The purpose of this review is to present an analytical approach designed to understand this regulation from a chemical perspective. By investigating the solution interactions between all combinations of molecules, protein-protein, protein-ligand, and protein-DNA, and the interplay between them, it is possible to determine the relative free energies of the different configurations of the regulatory complex. This governs their distribution and thereby controls the biological activity. To illustrate the approach, we will address the molecular basis for cooperativity in the bacteriophage lambda, lysogenic-lytic switch mechanism, a system that has long served as a paradigm for gene regulation. The driving force for cooperativity in the assembly of gene regulatory complexes is generally thought to be provided by direct protein-protein interactions. However, other interactions mediated by both proteins and DNA are also involved and may be critical to the regulatory mechanism. We will review advances over the past several years in the application of biophysical chemical methods to investigate protein-protein and protein-DNA interactions. Many of these applications were first employed for the lambda system. In addition to describing the physical basis for the methods, we will focus on the unique information that can be gained and how to combine the information obtained from several techniques to develop a comprehensive view of the critical regulatory interactions.
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Affiliation(s)
- D F Senear
- Department of Molecular Biology and Biochemistry, University of California at Irvine, Irvine, California, 92697, USA. dfsenear.uci.edu
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18
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Sheridan SD, Benham CJ, Hatfield GW. Activation of gene expression by a novel DNA structural transmission mechanism that requires supercoiling-induced DNA duplex destabilization in an upstream activating sequence. J Biol Chem 1998; 273:21298-308. [PMID: 9694890 DOI: 10.1074/jbc.273.33.21298] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have previously demonstrated that integration host factor (IHF)-mediated activation of transcription from the ilvPG promoter of Escherichia coli requires a supercoiled DNA template and occurs in the absence of specific interactions between IHF and RNA polymerase. In this report, we describe a novel, supercoiling-dependent, DNA structural transmission mechanism for this activation. We provide theoretical evidence for a supercoiling-induced DNA duplex destabilized (SIDD) structure in the A + T-rich, ilvPG regulatory region between base pair positions +1 and -160. We show that the region of this SIDD sequence immediately upstream of an IHF binding site centered at base pair position -92 is, in fact, destabilized by superhelical stress and that this duplex destabilization is inhibited by IHF binding. Thus, in the presence of IHF, the negative superhelical twist normally absorbed by this DNA structure in the promoter distal half of the SIDD sequence is transferred to the downstream portion of the SIDD sequence containing the ilvPG promoter site. This IHF-mediated translocation of superhelical energy facilitates duplex destabilization in the -10 region of the downstream ilvPG promoter and activates transcription by increasing the rate of open complex formation.
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Affiliation(s)
- S D Sheridan
- Department of Microbiology and Molecular Genetics, College of Medicine, University of California, Irvine, California 92697, USA
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19
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Howe MM. Bacteriophage Mu. Mol Microbiol 1998. [DOI: 10.1007/978-3-642-72071-0_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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20
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Desmet L, Gama MJ, Laachouch JE, Petrescu I, Rousseau P, Toussaint A. In vivo mutational analysis of bacteriophage Mu operators. Res Microbiol 1997; 148:101-8. [PMID: 9765791 DOI: 10.1016/s0923-2508(97)87641-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
In bacteria lysogenic for bacteriophage Mu, the phage repressor binds to a tripartite operator region, O1,O2,O3, to repress the lytic promoter pE, located in O2, and negatively autoregulate its own synthesis at the pCM promoter located in O3. We isolated and characterized operator mutations which lead to derepression of pE. Their location in the first and third repressor-consensus-binding sequences in O2 confirms the importance of these sites for repressor/operator interactions.
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Affiliation(s)
- L Desmet
- Laboratoire de Génétique des Procaryotes, Université Libre de Bruxelles, Rhode St Genèse Belgium
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21
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Parekh BS, Sheridan SD, Hatfield GW. Effects of integration host factor and DNA supercoiling on transcription from the ilvPG promoter of Escherichia coli. J Biol Chem 1996; 271:20258-64. [PMID: 8702758 DOI: 10.1074/jbc.271.34.20258] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Integration host factor (IHF) activates transcription from the ilvPG promoter by severely distorting the DNA helix in an upstream region of a supercoiled DNA template in a way that alters the structure of the DNA in the downstream promoter region and facilitates open complex formation. In this report, the in vivo and in vitro influence of DNA supercoiling on transcription from this promoter is examined. In the absence of IHF, promoter activity increases with increased DNA supercoiling. In the presence of IHF, the same increases in superhelical DNA densities result in larger increases in promoter activity until a maximal activation of 5-fold is obtained. However, the relative transcriptional activities of the promoter in the presence and absence of IHF at any given DNA superhelical density remains the same. Thus, IHF and increased DNA supercoiling activate transcription by different mechanisms. Also, IHF binds with equal affinities to its target site on linear and supercoiled DNA templates. Therefore, IHF binding does not activate transcription simply by increasing the local negative supercoiling of the DNA helix in the downstream promoter region or by differential binding to relaxed and supercoiled DNA templates.
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Affiliation(s)
- B S Parekh
- Department of Microbiology and Molecular Genetics, College of Medicine, University of California, Irvine, California 92697, USA
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22
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Abstract
Many modeling studies of supercoiled DNA are based on equilibrium structures from theoretical calculations or energy minimization. Since closed circular DNAs are flexible, it is possible that errors are introduced by calculating properties from a single minimum energy structure, rather than from a complete thermodynamic ensemble. We have investigated this question using molecular dynamics simulations on a low resolution molecular mechanics model in which each base pair is represented by three points (a plane). This allows the inclusion of sequence-dependent variations of tip, inclination, and twist. Three kinds of sequences were tested: (1) homogeneous DNA, in which all base pairs have the helicoidal parameters of an ideal, average B-DNA; (2) random sequence DNA; and (3) curved DNA. We examined the rate of convergence of various structural parameters. Convergence for most of these is slowest for homogeneous sequences, more rapid for random sequences, and most rapid for curved sequences. The most slowly converging parameter is the antipodes profile. In a plasmid with N base pairs (bp), the antipodes distance is the distance dij from base pair i to base pair j halfway around the plasmid, j = i + N/2. The antipodes profile at time tau is a plot of dij over the range i = 1, N/2. In a homogeneous plasmid, convergence requires that the antipodes profile averaged over time must be flat. Even in the small plasmids examined here, the average properties of the ensembles were found to differ from those of static equilibrium structures. These effects will be even more dramatic for larger plasmids. Further, average and dynamic properties are affected by both plasmid size and sequence.
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Affiliation(s)
- D Sprous
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham 35294, USA
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23
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Tan RK, Sprous D, Harvey SC. Molecular dynamics simulations of small DNA plasmids: effects of sequence and supercoiling on intramolecular motions. Biopolymers 1996; 39:259-78. [PMID: 8679953 DOI: 10.1002/(sici)1097-0282(199608)39:2<259::aid-bip12>3.0.co;2-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Small (600 base pair) DNA plasmids were modeled with a simplified representation (3DNA) and the intramolecular motions were studied using molecular mechanics and molecular dynamics techniques. The model is detailed enough to incorporate sequence effects. At the same time, it is simple enough to allow long molecular dynamics simulations. The simulations revealed that large-scale slithering occurs in a homogeneous sequence. In a heterogeneous sequence, containing numerous small intrinsic curves, the centers of the curves are preferentially positioned at the tips of loops. With more curves than loop tips (two in unbranched supercoiled DNA), the heterogeneous sequence plasmid slithers short distances to reposition other curves into the loop tips. However, the DNA is immobilized most of the time, with the loop tips positioned over a few favored curve centers. Branching or looping also appears in the heterogeneous sequence as a new method of repositioning the loop tips. Instead of a smooth progression of increasing writhing with increasing linking difference, theoretical studies have predicted that there is a threshold between unwrithed and writhed DNA at a linking difference between one and two. This has previously been observed in simulations of static structures and is demonstrated here for dynamic homogeneous closed DNA. Such an abrupt transition is not found in the heterogeneous sequence in both the static and dynamic cases.
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Affiliation(s)
- R K Tan
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham 35205-0005, USA
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24
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Both an altered DNA structure and cellular proteins are involved in protecting a triplex forming an oligopurine-rich sequence from dam methylation inE. coli. Biochem Genet 1996. [DOI: 10.1007/bf00553664] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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25
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Klysik J. Both an altered DNA structure and cellular proteins are involved in protecting a triplex forming an oligopurine-rich sequence from Dam methylation in E. coli. Biochem Genet 1996; 34:165-78. [PMID: 8813050 DOI: 10.1007/bf02407017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
When the 4-bp Dam recognition sequence was placed between two d(GA)7 tracts, it became severely undermethylated in JM101 Escherichia coli cells compared to other Dam sequences in the same plasmid DNA. This site specific undermethylation was also detected on supercoiled molecules in vitro. Mutational analysis indicated that undermethylation is related to the capacity of the oligopurine tract to adopt the H-DNA conformation. In addition, chemical probing of the cells was consistent with a cellular protein bound to the DNA. Therefore it is likely that the combination of altered DNA conformation and a cellular protein leads to Dam-site protection. We also found that the site-specific undermethylation is detectable in certain E. coli strains only.
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Affiliation(s)
- J Klysik
- Institute of Biosciences and Technology, Texas A&M University, Texas Medical Center, Houston 77030, USA
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26
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Higgins NP, Yang X, Fu Q, Roth JR. Surveying a supercoil domain by using the gamma delta resolution system in Salmonella typhimurium. J Bacteriol 1996; 178:2825-35. [PMID: 8631670 PMCID: PMC178017 DOI: 10.1128/jb.178.10.2825-2835.1996] [Citation(s) in RCA: 96] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
A genetic system was developed to investigate the supercoil structure of bacterial chromosomes. New res-carrying transposons were derived from MudI1734 (MudJr1 and MudJr2) and Tn10 (Tn10dGn). The MudJr1 and MudJr2 elements each have a res site in opposite orientation so that when paired with a Tn10dGn element in the same chromosome, one MudJr res site will be ordered as a direct repeat. Deletion formation was studied in a nonessential region (approximately 100 kb) that extends from the his operon through the cob operon. Strains with a MudJr insertion in the cobT gene at the 5' end of the cob operon plus a Tn10dGn insertion positioned either clockwise or counterclockwise from cobT were exposed to a burst of RES protein. Following a pulse of resolvase expression, deletion formation was monitored by scoring the loss of the Lac+ phenotype or by loss of tetracycline resistance. In exponentially growing populations, deletion products appeared quickly in some cells (in 10 min) but also occurred more than an hour after RES induction. The frequency of deletion (y) diminished with increasing distance (x) between res sites. Results from 15 deletion intervals fit the exponential equation y = 120 . 10(-0.02x). We found that res sites can be plectonemically interwound over long distances ( > 100 kb) and that barriers to supercoil diffusion are placed stochastically within the 43- to 45-min region of the chromosome.
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Affiliation(s)
- N P Higgins
- Department of Biochemistry, University of Alabama at Birmingham, 35294-2170, USA.
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27
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Rousseau P, Bétermier M, Chandler M, Alazard R. Interactions between the repressor and the early operator region of bacteriophage Mu. J Biol Chem 1996; 271:9739-45. [PMID: 8621652 DOI: 10.1074/jbc.271.16.9739] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The repressor of bacteriophage Mu, c, binds to three operator sites, O1, O2, and O3, overlapping two divergent promoters, which regulate the lytic and lysogenic pathways. Its binding to this operator region generates several complexes, which were analyzed by DNase I protection experiments. We demonstrate that c first binds to two 11-base pair partially repeated sequences in O2 that could represent "core" binding sites for the repressor. This initial interaction serves as an organizer of a more complex nucleoprotein structure in which O2, O1, and O3 become successively occupied. The quaternary structure of the repressor was also investigated. Size exclusion chromatography and protein-protein crosslinking experiments with chemicals that possess linking arms of various lengths indicate that the repressor oligomerizes in solution. A model is proposed describing the successive interactions of c with the operator sites O2, O1, and O3 leading to the elaboration of a higher order structure in which the early lytic functions are repressed.
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Affiliation(s)
- P Rousseau
- Laboratoire de Microbiologie et Genetique Moleculaires, CNRS, Toulouse, France
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28
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Affiliation(s)
- B D Lavoie
- Department of Biochemistry, University of Western Ontario, London, Canada
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29
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Betermier M, Rousseau P, Alazard R, Chandler M. Mutual stabilisation of bacteriophage Mu repressor and histone-like proteins in a nucleoprotein structure. J Mol Biol 1995; 249:332-41. [PMID: 7783197 DOI: 10.1006/jmbi.1995.0300] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Integration host factor (IHF) binds in a sequence-specific manner to the bacteriophage Mu early operator. It participates with bound Mu repressor, c, in building stable, large molecular mass nucleoprotein complexes in vitro and enhances repression of early transcription in vivo. We demonstrate that, when the specific IHF binding site with the operator is mutated, the appearance of large molecular mass complexes still depends on IHF and c, but the efficiency of their formation is reduced. Moreover, the IHF-like HU protein, which binds DNA in a non-sequence-specific way, can substitute for IHF and participate in complex formation. Since the complexes require both c and a host factor (IHF or HU), the results imply that these proteins stabilise each other within the nucleoprotein structures. These results suggest that IHF and HU are directed to the repressor-operator complexes, even in the absence of detectable sequence-specific binding. This could be a consequence of their preferential recognition of DNA containing a distortion such as that introduced by repressor binding to the operator. The histone-like proteins could then stabilise the nucleoprotein complexes simply by their capacity to maintain a bend in DNA rather than by specific protein-protein interactions with c. This model is supported by the observation that the unrelated eukaryotic HMG-1 protein, which exhibits a similar marked preference for structurally deformed DNA, is also able to participate in the formation of higher-order complexes with c and the operator DNA.
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Affiliation(s)
- M Betermier
- Laboratory of Molecular Genetics and Microbiology, C.N.R.S., Toulouse, France
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30
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Abstract
This article examines the published evidence in support of the classification of organisms into three groups (Bacteria, Archae, and Eukarya) instead of two groups (prokaryotes and eukaryotes) and summarizes the comparative biochemistry of each of the known histone-like, nucleoid DNA-binding proteins. The molecular structures and amino acid sequences of Archae are more similar to those of Eukarya than of Bacteria, with a few exceptions. Cytochemical methodology employed for localizing these proteins in archaeal and bacterial cells has also been reviewed. It is becoming increasingly apparent that these proteins participate both in the organization of DNA and in the control of gene expression. Evidence obtained from biochemical properties, structural and functional differences, and the ultrastructural location of these proteins, as well as from gene mutations clearly justifies the division of prokaryotes into bacterial and archaeal groups. Indeed, chromosomes, whether they be nuclear, prokaryotic, or organellar, are invariably complexed with abundant, small, basic proteins that bind to DNA with low sequence specificity. These proteins include the histones, histone-like proteins, and nonhistone high mobility group (HMG) proteins.
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Affiliation(s)
- M A Hayat
- Department of Biology, Kean College of New Jersey Union 07083, USA
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31
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Dove SL, Dorman CJ. The site-specific recombination system regulating expression of the type 1 fimbrial subunit gene of Escherichia coli is sensitive to changes in DNA supercoiling. Mol Microbiol 1994; 14:975-88. [PMID: 7715458 DOI: 10.1111/j.1365-2958.1994.tb01332.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We have studied the effect of altering the in vivo level of DNA supercoiling on the phase-variable expression of the Escherichia coli fimA gene. Transcription from the fimA promoter was unaffected by changes in DNA supercoiling whether caused by the introduction of a topA::Tn10 mutation or by inhibition of DNA gyrase with the antibiotic novobiocin. However, inversion of the fimA promoter fragment was altered in response to perturbation of DNA supercoiling. Specifically, inactivation of topA reduced the rate of promoter fragment inversion in both the ON-to-OFF and the OFF-to-ON directions. This effect correlated with the loss of functional topA and not with the global level of DNA supercoiling. Inhibition of DNA gyrase introduced a bias in favour of the OFF-to-ON inversion; the ON-to-OFF inversion was affected only slightly. Changes in expression of fimB, the gene coding for the recombinase that catalyses fimA promoter fragment inversion in the strains used in this study, did not correlate with effects on fimA phase variation: we found that transcription of fimB was inhibited by loss of functional topA and was enhanced by inhibition of DNA gyrase in a manner that correlated well with the global level of in vivo DNA supercoiling. A model is presented to account for the effects of lost topoisomerase function on fimA gene expression.
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MESH Headings
- Bacterial Proteins/genetics
- Base Sequence
- DNA Probes/genetics
- DNA Topoisomerases, Type I/genetics
- DNA Transposable Elements
- DNA, Bacterial/chemistry
- DNA, Bacterial/genetics
- DNA, Superhelical/chemistry
- DNA, Superhelical/genetics
- Escherichia coli/genetics
- Escherichia coli/metabolism
- Fimbriae Proteins
- Fimbriae, Bacterial
- Gene Expression Regulation, Bacterial
- Genes, Bacterial
- Molecular Sequence Data
- Mutation
- Novobiocin/pharmacology
- Nucleic Acid Conformation
- Promoter Regions, Genetic
- Recombination, Genetic
- Topoisomerase II Inhibitors
- Transcription, Genetic
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Affiliation(s)
- S L Dove
- Department of Biochemistry, University of Dundee, UK
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32
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Transcription induces the formation of a stable RNA.DNA hybrid in the immunoglobulin alpha switch region. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)31881-1] [Citation(s) in RCA: 106] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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33
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Bétermier M, Poquet I, Alazard R, Chandler M. Involvement of Escherichia coli FIS protein in maintenance of bacteriophage mu lysogeny by the repressor: control of early transcription and inhibition of transposition. J Bacteriol 1993; 175:3798-811. [PMID: 8389742 PMCID: PMC204797 DOI: 10.1128/jb.175.12.3798-3811.1993] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The Escherichia coli FIS (factor for inversion stimulation) protein has been implicated in assisting bacteriophage Mu repressor, c, in maintaining the lysogenic state under certain conditions. In a fis strain, a temperature-inducible Mucts62 prophage is induced at lower temperatures than in a wild-type host (M. Bétermier, V. Lefrère, C. Koch, R. Alazard, and M. Chandler, Mol. Microbiol. 3:459-468, 1989). Increasing the prophage copy number rendered Mucts62 less sensitive to this effect of the fis mutation, which thus seems to depend critically on the level of repressor activity. The present study also provides evidence that FIS affects the control of Mu gene expression and transposition. As judged by the use of lac transcriptional fusions, repression of early transcription was reduced three- to fourfold in a fis background, and this could be compensated by an increase in cts62 gene copy number. c was also shown to inhibit Mu transposition two- to fourfold less strongly in a fis host. These modulatory effects, however, could not be correlated to sequence-specific binding of FIS to the Mu genome, in particular to the strong site previously identified on the left end. We therefore speculate that a more general function of FIS is responsible for the observed modulation of Mu lysogeny.
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Affiliation(s)
- M Bétermier
- Molecular Genetics and Microbiology Laboratory, Centre National de la Recherche Scientifique UPR 9007, Toulouse, France
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34
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Kano Y, Yasuzawa K, Tanaka H, Imamoto F. Propagation of phage Mu in IHF-deficient Escherichia coli in the absence of the H-NS histone-like protein. Gene 1993; 126:93-7. [PMID: 8472963 DOI: 10.1016/0378-1119(93)90594-s] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Integration host factor (IHF) is known to be required for the expression of early genes and formation of the transpososome of mutator phage Mu. Prophage Mucts62 was stably maintained at 30 degrees C and proliferated effectively after thermal induction at 42 degrees C in an Escherichia coli mutant defective in the histone-like H-NS and IHF proteins. No IHF activity was detected in cells lacking H-NS and IHF; cells could not be transformed with plasmid pCL1920, which is based on the pSC101 replicon whose replication requires IHF. No difference in the superhelical densities of the reporter plasmid was detected in the H-NS, IHF null mutant and parental cells. From these results it is concluded that IHF is not essential for Mu development. These results also suggest that H-NS may function as a silencer for Pe operon expression and that IHF overcomes the inhibitory effect of H-NS.
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Affiliation(s)
- Y Kano
- Department of Molecular Genetics, Kyoto Pharmaceutical University, Japan
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35
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Abstract
Protein-nucleic acid interactions are crucial in the regulation of many fundamental cellular processes. The nature of these interactions is susceptible to analysis by a variety of methods, but the combination of high analytical power and technical simplicity offered by the gel retardation (band shift) technique has made this perhaps the most widely used such method over the last decade. This procedure is based on the observation that the formation of protein-nucleic complexes generally reduces the electrophoretic mobility of the nucleic acid component in the gel matrix. This review attempts to give a simplified account of the physical basis of the behavior of protein-nucleic acid complexes in gels and an overview of many of the applications in which the technique has proved especially useful. The factors which contribute most to the resolution of the complex from the naked nucleic acid are the gel pore size, the relative mass of protein compared with nucleic acid, and changes in nucleic acid conformation (bending) induced by binding. The consequences of induced bending on the mobility of double-strand DNA fragments are similar to those arising from sequence-directed bends, and the latter can be used to help characterize the angle and direction of protein-induced bends. Whether a complex formed in solution is actually detected as a retarded band on a gel depends not only on resolution but also on complex stability within the gel. This is strongly influenced by the composition and, particularly, the ionic strength of the gel buffer. We discuss the applications of the technique to analyzing complex formation and stability, including characterizing cooperative binding, defining binding sites on nucleic acids, analyzing DNA conformation in complexes, assessing binding to supercoiled DNA, defining protein complexes by using cell extracts, and analyzing biological processes such as transcription and splicing.
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Affiliation(s)
- D Lane
- Laboratory of Molecular Genetics and Microbiology, Centre National de la Recherche Scientifique, Toulouse, France
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36
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Santero E, Hoover TR, North AK, Berger DK, Porter SC, Kustu S. Role of integration host factor in stimulating transcription from the sigma 54-dependent nifH promoter. J Mol Biol 1992; 227:602-20. [PMID: 1404379 DOI: 10.1016/0022-2836(92)90211-2] [Citation(s) in RCA: 94] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In a wide variety of nitrogen-fixing organisms among the Purple Bacteria (large division of Gram-negative bacteria) the nitrogen fixation (nif) operons are transcribed by an alternative holoenzyme form of RNA polymerase, sigma 54-holoenzyme. Transcription depends on the activator protein NIFA (nitrogen fixation protein A), which catalyzes isomerization of closed complexes between this polymerase and a promoter to transcriptionally productive open complexes. NIFA-mediated activation of transcription from the nifH promoter of Klebsiella pneumoniae is greatly stimulated by the integration host factor IHF, which binds to a site between the upstream binding site for NIFA and the promoter, and bends the DNA. IHF fails to stimulate activation of transcription from this promoter by another activator of sigma 54-holoenzyme, NTRC (nitrogen regulatory protein C), which lacks a specific binding site in the nifH promoter region. As predicted, if the IHF-induced bend facilitates interaction between NIFA and sigma 54-holoenzyme, substitution of an NTRC-binding site for the NIFA-binding site allowed IHF to stimulate NTRC-mediated activation of transcription from the nifH promoter. The stimulation was of the same order of magnitude as that for NIFA in the native configuration of the promoter-regulatory region (up to 20-fold). With purified NTRC and the substitution construct we could demonstrate that stimulation by IHF in a purified transcription system was comparable to that in a crude coupled transcription-translation system, indicating that the stimulation in the crude system could be accounted for by IHF. The IHF stimulation was observed on linear as well as supercoiled templates, indicating that the geometric requirements are relatively simple. We have attempted to visualize the arrangement of proteins on DNA fragments carrying the nifH promoter-regulatory region of K. pneumoniae by electron microscopy. IHF stimulated NIFA-mediated activation of transcription from the nifH and nifD promoters of Bradyrhizobium japonicum and less so from the nifH promoters of Rhizobium meliloti and Thiobacillus ferrooxidans, consistent with previous observations that stimulation is greatest at promoters that are weak binding sites for sigma 54-holoenzyme in closed complexes.
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Affiliation(s)
- E Santero
- Department of Plant Pathology, University of California, Berkeley 94720
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37
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Role of the A protein-binding sites in the in vitro transposition of mu DNA. A complex circuit of interactions involving the mu ends and the transpositional enhancer. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)88651-9] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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38
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Kukolj G, DuBow M. Integration host factor activates the Ner-repressed early promoter of transposable Mu-like phage D108. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)37118-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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39
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Alazard R, Bétermier M, Chandler M. Escherichia coli integration host factor stabilizes bacteriophage Mu repressor interactions with operator DNA in vitro. Mol Microbiol 1992; 6:1707-14. [PMID: 1386645 DOI: 10.1111/j.1365-2958.1992.tb00895.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Using gel retardation and DNase I protection techniques, we have demonstrated that the Escherichia coli integration host factor (IHF) stabilizes the interaction between Mu repressor and its cognate operator-binding sites in vitro. These results are discussed in terms of a model in which IHF may commit the phage to the lytic or lysogenic pathway depending on the occupancy of the operator sites by the repressor.
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Affiliation(s)
- R Alazard
- Centre de Recherches en Biochimie et Génétique Cellulaires, Toulouse, France
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40
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Nordström K, Uhlin BE. Runaway–Replication Plasmids as Tools to Produce Large Quantities of Proteins from Cloned Genes in Bacteria. Nat Biotechnol 1992; 10:661-6. [PMID: 1368887 DOI: 10.1038/nbt0692-661] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Here we review the properties and uses of runaway-replication vectors, a class of versatile plasmids discovered and developed in Escherichia coli. They are based on the IncFII plasmid, R1, in which an antisense RNA (CopA RNA) negatively controls the formation of a protein that is rate-limiting for replication. The copy number of the plasmid is determined by the balance between the rates of formation of CopA RNA and RepA mRNA. A small increase in the rate of formation of the latter drastically reduces the rate of formation of CopA RNA due to convergent transcription, which may lead to a total loss of copy number control (runaway replication), resulting in massive DNA amplification, and plasmid copy numbers up to 1000 per genome. Since this amplification occurs in the presence of protein synthesis, the protein that is encoded by a cloned gene can also be amplified, and may constitute 10-50% of the total protein.
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Affiliation(s)
- K Nordström
- Department of Microbiology, Uppsala University, Sweden
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41
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Gama MJ, Toussaint A, Higgins NP. Stabilization of bacteriophage Mu repressor-operator complexes by the Escherichia coli integration host factor protein. Mol Microbiol 1992; 6:1715-22. [PMID: 1386646 DOI: 10.1111/j.1365-2958.1992.tb00896.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
All of the previously described effects of integration host factor (IHF) on bacteriophage Mu development have supported the view that IHF favours transposition-replication over the alternative state of lysogenic phage growth. In this report we show that, consistent with a model in which Mu repressor binding to its operators requires a particular topology of the operator DNA, IHF stimulates repressor binding to the O1 and O2 operators and enhances Mu repression. IHF would thus be one of the keys, besides supercoiling and the H-NS protein, that lock the operator region into the appropriate topological conformation for high-affinity binding not only of the phage transposase but also of the phage repressor.
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Affiliation(s)
- M J Gama
- Unité Transposition Bactérienne, Université Libre de Bruxelles, Rhode Saint Genèse, Belgium
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42
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Surette MG, Chaconas G. The Mu transpositional enhancer can function in trans: requirement of the enhancer for synapsis but not strand cleavage. Cell 1992; 68:1101-8. [PMID: 1312394 DOI: 10.1016/0092-8674(92)90081-m] [Citation(s) in RCA: 61] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The phage Mu transpositional enhancer has been previously shown to stimulate the initial rate of the Mu DNA strand transfer reaction by a factor of 100. We now show that the Mu enhancer can function in trans on an unlinked DNA molecule. This activity is greatly facilitated by the presence of a free DNA end proximal to the enhancer element. Function of the enhancer in trans does not alter either the requirement for donor DNA supercoiling or for the two Mu ends to be in their proper orientation on the donor plasmid. An important consequence of these findings is that we have been able to evaluate directly the step in the transposition reaction for which the enhancer is required. We show that the role of the enhancer is limited to promoting productive synapsis; efficient strand cleavage can occur in the absence of the enhancer.
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Affiliation(s)
- M G Surette
- Department of Biochemistry, University of Western Ontario, London, Canada
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43
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Paolozzi L, Ghelardini P. A case of lysogenic conversion: modification of cell phenotype by constitutive expression of the Mu gem operon. Res Microbiol 1992; 143:237-43. [PMID: 1448611 DOI: 10.1016/0923-2508(92)90015-g] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- L Paolozzi
- Dipartimento di Biologia, II Università di Roma Tor Vergata
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44
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Geuskens V, Vogel JL, Grimaud R, Desmet L, Higgins NP, Toussaint A. Frameshift mutations in the bacteriophage Mu repressor gene can confer a trans-dominant virulent phenotype to the phage. J Bacteriol 1991; 173:6578-85. [PMID: 1833383 PMCID: PMC208995 DOI: 10.1128/jb.173.20.6578-6585.1991] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Virulent mutations in the bacteriophage Mu repressor gene were isolated and characterized. Recombination and DNA sequence analysis have revealed that virulence is due to unusual frameshift mutations which change several C-terminal amino acids. The vir mutations are in the same repressor region as the sts amber mutations which, by eliminating several C-terminal amino acids, suppress thermosensitivity of repressor binding to the operators by its N-terminal domain (J. L. Vogel, N. P. Higgins, L. Desmet, V. Geuskens, and A. Toussaint, unpublished data). Vir repressors bind Mu operators very poorly. Thus the Mu repressor C terminus, either by itself or in conjunction with other phage or host proteins, tunes the DNA-binding properties at the repressor N terminus.
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Affiliation(s)
- V Geuskens
- Laboratoire de Génétique, Université Libre de Bruxelles, Rhode Saint Genèse, Belgium
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45
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Vogel JL, Li ZJ, Howe MM, Toussaint A, Higgins NP. Temperature-sensitive mutations in the bacteriophage Mu c repressor locate a 63-amino-acid DNA-binding domain. J Bacteriol 1991; 173:6568-77. [PMID: 1833382 PMCID: PMC208994 DOI: 10.1128/jb.173.20.6568-6577.1991] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Phage Mu's c gene product is a cooperative regulatory protein that binds to a large, complex, tripartite 184-bp operator. To probe the mechanism of repressor action, we isolated and characterized 13 phage mutants that cause Mu to undergo lytic development when cells are shifted from 30 to 42 degrees C. This collection contained only four mutations in the repressor gene, and all were clustered near the N terminus. The cts62 substitution of R47----Q caused weakened specific DNA recognition and altered cooperativity in vitro. A functional repressor with only 63 amino acids of Mu repressor fused to a C-terminal fragment of beta-galactosidase was constructed. This chimeric protein was an efficient repressor, as it bound specifically to Mu operator DNA in vitro and its expression conferred Mu immunity in vivo. A DNA looping model is proposed to explain regulation of the tripartite operator site and the highly cooperative nature of repressor binding.
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Affiliation(s)
- J L Vogel
- Department of Biochemistry, University of Alabama, Birmingham 35294
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46
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Tsui P, Huang L, Freundlich M. Integration host factor binds specifically to multiple sites in the ompB promoter of Escherichia coli and inhibits transcription. J Bacteriol 1991; 173:5800-7. [PMID: 1885551 PMCID: PMC208313 DOI: 10.1128/jb.173.18.5800-5807.1991] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Escherichia coli integration host factor (IHF) is a DNA-binding protein that participates in gene regulation, site-specific recombination, and other processes in E. coli and some of its bacteriophages and plasmids. In the present study, we showed that IHF is a direct negative effector of the ompB operon of E. coli. Gel retardation experiments and DNase I footprinting studies revealed that IHF binds to three sites in the ompB promoter region. In vitro transcription from ompB promoter fragments was specifically blocked by IHF. In vivo experiments showed that IHF is a negative effector of ompB expression in growing cells. Analysis of IHF binding site mutations strongly suggested that IHF binding in the ompB promoter region is necessary for the negative effects seen in vivo.
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Affiliation(s)
- P Tsui
- Department of Biochemistry and Cell Biology, State University of New York, Stony Brook 11794-5212
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47
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Cornelis GR, Sluiters C, Delor I, Geib D, Kaniga K, Lambert de Rouvroit C, Sory MP, Vanooteghem JC, Michiels T. ymoA, a Yersinia enterocolitica chromosomal gene modulating the expression of virulence functions. Mol Microbiol 1991; 5:1023-34. [PMID: 1956283 DOI: 10.1111/j.1365-2958.1991.tb01875.x] [Citation(s) in RCA: 147] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The virulence functions of Yersinia enterocolitica include the pYV-encoded Yop proteins and YadA adhesin as well as the chromosome-encoded enterotoxin, Yst. The yop and yadA genes form a temperature-activated regulon controlled by the transcriptional activator VirF. Gene virF, also localized on pYV, is itself thermoinduced in the absence of other pYV genes. The enterotoxin yst gene is silent in some collection strains including strain W22703. This paper describes two Tn5-Tc1 chromosomal insertion mutants of W22703 transcribing virF, and hence the yop and yadA genes, at low temperature. These mutants also resumed their production of Yst, with its typical temperature dependence. Both mutations were insertions in the same gene called ymoA for 'Yersinia modulator'. The cloned ymoA gene fully complemented the two mutations. Several properties of the mutants suggest that ymoA encodes a histone-like protein. According to the nucleic acid sequence, the product of ymoA is an 8064 Da protein rich in aspartic acid (9%), glutamic acid (9%) and lysine (10.5%), but the predicted amino acid sequence shows no similarity with any described histone-like protein. This work supports recent reports which propose a role for DNA topology and bacterial chromatin structure in thermoregulation of virulence functions.
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Affiliation(s)
- G R Cornelis
- Microbiol Pathogenesis Unit, International Institute of Cellular and Molecular Pathology, Brussels, Belgium
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48
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Richet E, Raibaud O. Supercoiling is essential for the formation and stability of the initiation complex at the divergent malEp and malKp promoters. J Mol Biol 1991; 218:529-42. [PMID: 2016744 DOI: 10.1016/0022-2836(91)90699-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
malEp and malKp are divergent and partially overlapping promoters of the Escherichia coli maltose regulon, whose activity depends on the presence of two transcriptional activators. MalT and CRP (cAMP receptor protein). Their activation involves a common 210 base-pair regulatory region encompassing multiple binding sites for both activators. Using a supercoiled plasmid containing malEp and malKp as template, purified proteins and a single-round transcription assay, we developed an in vitro system in which both promoters behave as in vivo. In this system, malEp and malKp are active only in the presence of both MalT and CRP, and various mutations in the MalT or CRP binding sites affect the promoters in the same way as they do in vivo. We showed that supercoiling plays a crucial role not only for the formation of the initiation complex at malEp and malKp but also for its stability. In addition, dimethylsulphate protection experiments provide evidence that the nucleoprotein complexes formed by CRP and MalT bound to malEp and malKp on supercoiled and relaxed DNA are different. We speculate that one of the roles of supercoiling might be to assist the assembly of a preinitiation complex involving the regulatory region DNA and several molecules of MalT and CRP.
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Affiliation(s)
- E Richet
- Unité de Génétique Moléculaire, URA 1149 du CNRS, Institut Pasteur, Paris, France
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49
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Integration host factor of Escherichia coli reverses the inhibition of R6K plasmid replication by pi initiator protein. J Bacteriol 1991; 173:1279-86. [PMID: 1991721 PMCID: PMC207252 DOI: 10.1128/jb.173.3.1279-1286.1991] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Integration host factor (IHF) protein is the only host-encoded protein known to bind and to affect replication of the gamma origin of Escherichia coli plasmid R6K. We examined the ability of R6K origins to replicate in cells lacking either of the two subunits of IHF. As shown previously, the gamma origin cannot replicate in IHF-deficient cells. However, this inability to replicate was relieved under the following conditions: underproduction of the wild-type pi replication protein of R6K or production of normal levels of mutant pi proteins which exhibit relaxed replication control. The copy number of plasmids containing the primary R6K origins (alpha and beta) is substantially reduced in IHF-deficient bacteria. Furthermore, replication of these plasmids is completely inhibited if the IHF-deficient strains contain a helper plasmid producing additional wild-type pi protein. IHF protein has previously been shown to bind to two sites within the gamma origin. These sites flank a central repeat segment which binds pi protein. We propose a model in which IHF binding to its sites reduces the replication inhibitor activity of pi protein at all three R6K origins.
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50
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Lee EC, MacWilliams MP, Gumport RI, Gardner JF. Genetic analysis of Escherichia coli integration host factor interactions with its bacteriophage lambda H' recognition site. J Bacteriol 1991; 173:609-17. [PMID: 1824766 PMCID: PMC207051 DOI: 10.1128/jb.173.2.609-617.1991] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The bacteriophage P22-based challenge phage system was used to study the binding of integration host factor (IHF) to its H' recognition site in the attP region of bacteriophage lambda. We constructed challenge phages that carried H' inserts in both orientations within the P22 Pant promoter, which is required for antirepressor synthesis. We found that IHF repressed expression of Pant from either challenge phage when expressed from an inducible Ptac promoter on a plasmid vector. Mutants containing changes in the H' inserts that decrease or eliminate IHF binding were isolated by selecting challenge phages that could synthesize antirepressor in the presence of IHF. Sequence analysis of 31 mutants showed that most changes were base pair substitutions within the H' insert. Approximately one-half of the mutants contained substitutions that changed base pairs that are part of the IHF consensus binding site; mutants were isolated that contained substitutions at six of the nine base pairs of the consensus site. Other mutants contained changes at base pairs between the two subdeterminants of the H' site, at positions that are not specified in the consensus sequence, and in the dA + dT-rich region that flanks the consensus region of the site. Taken together, these results show that single-base-pair changes at positions outside of the proposed consensus bases can weaken or drastically disrupt IHF binding to the mutated site.
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Affiliation(s)
- E C Lee
- Department of Microbiology, University of Illinois, Urbana 61801
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