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.
Deformation of DNA during site-specific recombination of bacteriophage lambda: replacement of IHF protein by HU protein or sequence-directed bends
DNA topology-mediated regulation of transcription initiation from the tandem promoters of the ilvGMEDA operon of Escherichia coli
HU and integration host factor function as auxiliary proteins in cleavage of phage lambda cohesive ends by terminase
Involvement of integration host factor (IHF) in maintenance of plasmid pSC101 in Escherichia coli: mutations in the topA gene allow pSC101 replication in the absence of IHF
Binding of integration host factor (IHF) to the ilvGp1 promoter of the ilvGMEDA operon of Escherichia coli K12
Stable DNA unwinding, not "breathing," accounts for single-strand-specific nuclease hypersensitivity of specific A+T-rich sequences
Integration host factor of Escherichia coli regulates early- and repressor transcription of bacteriophage Mu by two different mechanisms
Translational regulation is responsible for growth-rate-dependent and stringent control of the synthesis of ribosomal proteins L11 and L1 in Escherichia coli
Synergistic effect of himA and gyrB mutations: evidence that him functions control expression of ilv and xyl genes.
The facile generation of covalently closed, circular DNAs with defined negative superhelical densities
Mutations in the DNA gyrB gene that are temperature sensitive for lambda site-specific recombination, Mu growth, and plasmid maintenance.
A third recognition element in bacterial promoters: DNA binding by the alpha subunit of RNA polymerase
Promoter selectivity of Escherichia coli RNA polymerase E sigma 70 and E sigma 38 holoenzymes. Effect of DNA supercoiling.
Transcriptional activation by protein-induced DNA bending: evidence for a DNA structural transmission model
Comparison of DeltarelA strains of Escherichia coli and Salmonella enterica serovar Typhimurium suggests a role for ppGpp in attenuation regulation of branched-chain amino acid biosynthesis
In vivo and in vitro effects of integration host factor at the DmpR-regulated sigma(54)-dependent Po promoter
Mechanism of transcription activation at the comG promoter by the competence transcription factor ComK of Bacillus subtilis.
Integration of regulatory signals through involvement of multiple global regulators: control of the Escherichia coli gltBDF operon by Lrp, IHF, Crp, and ArgR
Transcriptional coupling between the divergent promoters of a prototypic LysR-type regulatory system, the ilvYC operon of Escherichia coli
Activation of transcription initiation from a stable RNA promoter by a Fis protein-mediated DNA structural transmission mechanism
The integration host factor (IHF) integrates stationary-phase and virulence gene expression in Salmonella enterica serovar Typhimurium
Inhibition of DNA supercoiling-dependent transcriptional activation by a distant B-DNA to Z-DNA transition.
Activation of gene expression by a novel DNA structural transmission mechanism that requires supercoiling-induced DNA duplex destabilization in an upstream activating sequence.
The effects of DNA supercoiling on the expression of operons of the ilv regulon of Escherichia coli suggest a physiological rationale for divergently transcribed operons
A quantitative model of a cooperative two-state equilibrium in DNA: experimental tests, insights, and predictions.
Role of upstream activation sequences and integration host factor in transcriptional activation by the constitutively active prokaryotic enhancer-binding protein PspF
Growth rate-related regulation of the ilvGMEDA operon of Escherichia coli K-12 is a consequence of the polar frameshift mutation in the ilvG gene of this strain
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