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  • 1
    Electronic Resource
    Electronic Resource
    Involvement of differential efficiency of transcription by Eσs and Eσ70 RNA polymerase holoenzymes in growth phase regulation of the Escherichia coli osmE promoter (2000)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 35 (2000), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Transcription of the gene osmE of Escherichia coli is inducible by elevated osmotic pressure and during the decelerating phase of growth. osmE expression is directed by a single promoter, osmEp. Decelerating phase induction of osmEp is dependent on the σs (RpoS) factor, whereas its osmotic induction is independent of σs. Purified Eσs and Eσ70 were both able to transcribe osmEpin vitro on supercoiled templates. In the presence of rpoD800, a mutation resulting in a thermosensitive σ70 factor, a shift to non-permissive temperature abolished induction of osmEp after an osmotic shock during exponential phase, but did not affect the decelerating phase induction. Point mutations affecting osmEp activity were isolated. Down-promoter mutations decreased transcription in both the presence and the absence of σs, indicating that the two forms of RNA polymerase holoenzyme recognize very similar sequence determinants on the osmE promoter. Three up-promoter mutations brought osmEp closer to the consensus of Eσ70-dependent promoters. The two variant promoters exhibiting the highest efficiency became essentially independent of σsin vivo. Our data suggest that Eσs transcribes wild-type osmEp with a higher efficiency than Eσ70. A model in which an intrinsic differential recognition contributes to growth phase-dependent regulation is proposed. Generalization of this model to other σs-dependent promoters is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2000.01758.x
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  • 2
    Electronic Resource
    Electronic Resource
    Interplay between global regulators of Escherichia coli : effect of RpoS, Lrp and H-NS on transcription of the gene osmC (1998)
    Oxford BSL : Blackwell Publishing Ltd
    Molecular microbiology 28 (1998), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The transcription of the osmC gene of Escherichia coli is regulated as a function of the phase of growth. It is induced during the decelerating phase, before entry into stationary phase. osmC expression is directed by two overlapping promoters, osmCp1 and osmCp2. osmCp2 is mainly transcribed by E-σs, the RNA polymerase using the σs (RpoS) sigma factor, and is responsible for the growth phase regulation. Transcription from osmCp1 is independent of σs. The leucine-responsive protein (Lrp) has been shown to bind the osmC promoter region in band shift experiments. In vivo analysis using osmC–lacZ transcriptional fusions demonstrated that Lrp affects the expression of both promoters. It represses the transcription of osmCp1 and activates the transcription of osmCp2 by E-σs. An absence of Lrp results in an increase in the amount of RpoS during exponential growth in minimal medium. The nucleoid-associated protein H-NS also represses osmC transcription from both promoters. However, this happens through different mechanisms. The effect on osmCp2 is probably mediated by the increase in σs concentration in the cytoplasm of hns− mutants, while the effect on osmCp1 is independent of σs. No binding of H-NS to the promoter region DNA could be detected, indicating that the effect on osmCp1 could also be indirect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1998.00855.x
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  • 3
    Electronic Resource
    Electronic Resource
    Growth-phase-dependent expression of the osmotically inducible gene osmC of Escherichia coli K-12 (1996)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 19 (1996), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The transcription of the osmotically inducible gene osmC of Escherichia coli is initiated by two overlapping promoters, osmCp1 and osmCp2. The existence of these two promoters was confirmed by site-directed mutagenesis. osmC transcription is regulated by the growth phase. In a medium of low osmotic pressure, expression of osmC is induced at the onset of decelerating phase and continues during the beginning of stationary phase. At elevated osmotic pressure, the induction occurs somewhat earlier during growth. Both promoters are repressed during early exponential phase. osmCp2 is induced during entry into stationary phase. Transcription from osmCp1, which is approximately 10-fold lower than that of osmCp2 in rich medium, starts during the mid-log phase and stops in early stationary phase. In the absence of σS, the stationary-phase sigma factor encoded by rpoSosmCp2 expression is much reduced while expression of osmCp1 is unaffected. As a consequence, the regulation of osmC as a function of growth is at least partially independent of σS
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1996.418945.x
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  • 4
    Electronic Resource
    Electronic Resource
    Characterization of the osmotically inducible gene osmE of Escherichia coli K-12 (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 16 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: osmE, an osmotically inducible gene of Escherichia coli, was physically mapped on the bacterial chromosome, cloned and sequenced. osmE appeared to encode a 12 021 Da protein of unknown function, with a lipoprotein-type signal sequence at the amino-terminus. The osmE reading frame was confirmed by sequencing the junction of an osmE-phoA gene fusion. osmE was demonstrated to be transcribed as a single cistron. A φ[osmEp–lac] operon fusion was constructed, and analysis of its expression demonstrated that osmE osmotic regulation probably occurs at the transcriptional level. The osmE promoter was identified by both S1 nuclease and primer extension mapping of the 5′ end of the osmE mRNA, by deletion analysis and by identification of a point mutation reducing its activity. Sequence information sufficient for expression and osmotic regulation is present on a DNA fragment extending from positions -37 to + 52 with respect to the osmE transcription start. Unin-duced expression of the osmE-lac fusion was increased in the presence of mutations in the hns and himA genes. The osmE promoter overlaps a promoter for a gene transcribed in the opposite direction, efg. Transcription from the efg promoter is only weakly affected by osmotic pressure and is independent of the presence of an intact OsmE protein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.tb02418.x
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  • 5
    Electronic Resource
    Electronic Resource
    DNA supercoiling contributes to disconnect σS accumulation from σS-dependent transcription in Escherichia coli (2003)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 48 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The σS subunit of RNA polymerase is a key regulator of Escherichia coli transcription in stress conditions. σS accumulates in cells subjected to stresses such as an osmotic upshift or the entry into stationary phase. We show here that, at elevated osmolarity, σS accumulates long before the beginning of the σS-dependent induction of osmEp, one of its target promoters. A combination of in vivo and in vitro evidence indicates that a high level of DNA negative supercoiling inhibits transcription by EσS. The variations in superhelical densities occurring as a function of growth conditions can modulate transcription of a subset of σS targets and thereby contribute to the temporal disconnection between the accumulation of σS and σS-driven transcription. We propose that, in stress conditions leading to the accumulation of σS without lowering the growth rate, the level of DNA supercoiling acts as a checkpoint that delays the shift from the major (Eσ70) to the general stress (EσS) transcriptional machinery, retarding the induction of a subset of the σS regulon until the conditions become unfavourable enough to cause entry into stationary phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03461.x
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  • 6
    Electronic Resource
    Electronic Resource
    Osmoregulation in Lactococcus lactis: BusR, a transcriptional repressor of the glycine betaine uptake system BusA (2003)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 47 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The busA (opuA) locus of Lactococcus lactis encodes a glycine betaine uptake system. Transcription of busA is osmotically inducible and its induction after an osmotic stress is reduced in the presence of glycine betaine. Using a genetic screen in CLG802, an Escherichia coli strain carrying a lacZ transcriptional fusion expressed under the control of the busA promoter, we isolated a genomic fragment from the L. lactis subsp. cremoris strain MG1363, which represses transcription from busAp. The cloned locus responsible for this repression was identified as a gene present upstream from the busA operon, encoding a putative DNA binding protein. This gene was named busR. Electrophoretic mobility shift and footprinting experiments showed that BusR is able to bind a site that overlaps the busA promoter. Overexpression of busR in L. lactis reduced expression of busA. Its disruption led to increased and essentially constitutive transcription of busA at low osmolarity. Therefore, BusR is a major actor of the osmotic regulation of busA in L. lactis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03362.x
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  • 7
    Electronic Resource
    Electronic Resource
    RcsCDB His-Asp phosphorelay system negatively regulates the flhDC operon in Escherichia coli (2003)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 49 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The genes involved in flagellum synthesis, motility and chemotaxis in Escherichia coli are expressed in a hierarchical fashion. At the top of the hierarchy lies the master regulator FlhDC, required for the expression of the whole set of genes. The operon flhDC is controlled by numerous regulators including H-NS, CRP, EnvZ/OmpR, QseBC and LrhA. In the present work, we report that the flhDC operon is also negatively regulated by the His-Asp phosphorelay system RcsCDB. The regulation is potentiated by the RcsB cofactor RcsA. Genetic analysis indicates that an RcsAB box, located downstream of the promoter, is required for the regulation. The binding of RcsB and RcsA to this site was demonstrated by gel retardation and DNase I protection assays. In addition, mutation analysis suggests that RcsA-specific determinants lie in the right part of the ‘RcsAB box’.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03601.x
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  • 8
    Electronic Resource
    Electronic Resource
    σs-Dependent regulation of yehZYXW, which encodes a putative osmoprotectant ABC transporter of Escherichia coli (2004)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 236 (2004), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The Escherichia coli yehZYXW operon encodes a putative osmoprotectant uptake system of the ABC transporter family. yehZ is identical to osmF, an osmotically inducible gene identified previously. Construction and analysis of a yehZ–lacZ transcriptional fusion demonstrated that yehZ is inducible not only by osmolarity, but also upon entry into stationary phase. The osmotic and growth-phase regulations operate at a unique promoter, yehZp, and are totally dependent on the stress specific σ factor σs. The yehZYXW encoded ABC transporter appears as an additional element of the global stress response controlled by σs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2004.tb09650.x
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  • 9
    Electronic Resource
    Electronic Resource
    Analysis and DNA sequence of the osmoregulatedtreA gene encoding the periplasmic trehalase ofEscherichia coli K12 (1989)
    Springer
    Molecular genetics and genomics 217 (1989), S. 347-354 
    Details
    ISSN: 1617-4623
    Keywords: Osmoregulation ; Periplasmic protein ; Signal sequence ; phoA fusions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary ThetreA gene ofEscherichia coli K12 codes for a periplasmic trehalase that is induced by growth at high osmolarity. The position oftreA within a cloned chromosomal DNA fragment was identified by subcloning of restriction fragments and analysis of the gene product in minicells. The nucleotide sequence of thetreA coding region as well as its upstream control region was determined. ThetreA gene consists of 1695 bp encoding 565 amino acids. The amino-terminus of the mature trehalase was found to begin with the amino acid Glu at position 31 of the open reading frame. The first 30 amino acids resemble a typical signal sequence, consistent with trehalase being a secreted periplasmic enzyme. Two previously isolatedphoA fusions to theosmA gene were transferred by homologous recombination on to atreA-containing plasmid and found to be withintreA. Analysis of the hybrid genes and their gene products aided the localization oftreA and the determination of its direction of transcription within the cloned chromosomal segment. ThetreA-phoA fusions encoded hybrid proteins which could be found in the periplasm. We found that at high osmolarity the normal pathway for the uptake and utilization of trehalose is blocked. Therefore, the function of the periplasmic trehalase is to provide the cell with the ability to utilize trehalose at high osmolarity by splitting it into glucose molecules that can subsequently be taken up by the phosphotransferase-mediated uptake system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02464903
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  • 10
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    Osmotic regulation of transcription inLactococcus lactis: Ionic strength-dependent binding of the BusR repressor to thebusApromoter (2007)
    Wiley
    Details
    Publication Date: 2007-06-26
    Print ISSN: 0014-5793
    Electronic ISSN: 1873-3468
    Topics: Biology , Chemistry and Pharmacology
    Published by Wiley on behalf of Federation of European Biochemical Societies.
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