DNA topology-mediated regulation of transcription initiation from the tandem promoters of the ilvGMEDA operon of Escherichia coli

Pagel, John M.; Winkelman, J W; Adams, C W; Hatfield, G. Wesley

doi:10.1016/0022-2836(92)90460-2

Cited by 35 publications

(14 citation statements)

References 56 publications

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“…IHF-mediated activation of ilvp G 2 is not strictly dependent on the helical phasing or distance of the IHF-binding site relative to this promoter, suggesting that interactions between IHF and RNA polymerase or between upstream DNA sequences and RNA polymerase are not required (43). Instead, it appears that an IHF-induced DNA bend alters the structure of the ilvp G 2 Ϫ10 region so as to favor formation of an open complex (44).…”

Section: Discussionmentioning

confidence: 96%

Deletion analysis of the fis promoter region in Escherichia coli: antagonistic effects of integration host factor and Fis

et al. 1997

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Fis is a small DNA-binding and -bending protein in Escherichia coli that is involved in several different biological processes, including stimulation of specialized DNA recombination events and regulation of gene expression. fis protein and mRNA levels rapidly increase during early logarithmic growth phase in response to a nutritional upshift but become virtually undetectable during late logarithmic and stationary phases. We present evidence that the growth phase-dependent fis expression pattern is not determined by changes in mRNA stability, arguing in favor of regulation at the level of transcription. DNA deletion analysis of the fis promoter (fis P) region indicated that DNA sequences from ؊166 to ؊81, ؊36 to ؊26, and ؉107 to ؉366 relative to the transcription start site are required for maximum expression. A DNA sequence resembling the integration host factor (IHF) binding site centered approximately at ؊114 showed DNase I cleavage protection by IHF. In ihf cells, maximum cellular levels of fis mRNA were decreased more than 3-fold and transcription from fis P on a plasmid was decreased about 3.8-fold compared to those in cells expressing wild-type IHF. In addition, a mutation in the ihf binding site resulted in a 76 and 61% reduction in transcription from fis P on a plasmid in the presence or absence of Fis, respectively. Insertions of 5 or 10 bp between this ihf site and fis P suggest that IHF functions in a position-dependent manner. We conclude that IHF plays a role in stimulating transcription from fis P by interacting with a site centered approximately at ؊114 relative to the start of transcription. We also showed that although the fis P region contains six Fis binding sites, Fis site II (centered at ؊42) played a predominant role in autoregulation, Fis sites I and III (centered at ؉26 and ؊83, respectively) seemingly played smaller roles, and no role in negative autoregulation could be attributed to Fis sites IV, V, and VI (located upstream of site III). The fis P region from ؊36 to ؉7, which is not directly regulated by either IHF or Fis, retained the characteristic fis regulation pattern in response to a nutritional upshift.Fis is an 11.2-kDa DNA-binding and -bending protein that was first identified for its ability to stimulate DNA inversion reactions mediated by the Hin, Gin, and Cin family of recombinases (24, 29, 31). Hence, this protein was termed factor for inversion stimulation (Fis). Subsequently, Fis was shown to be involved in other cellular processes, including bacteriophage DNA excision and integration (2, 3, 50), regulation of initiation of DNA replication at oriC (12,19,54), and regulation of gene expression (13). Fis can stimulate transcription of rRNA and tRNA operons (23,36,47) and several structural genes (1, 20, 56) and can also negatively regulate the transcription of various genes, including its own (3,20,39,55). Roles played by Fis appear to be especially significant under conditions of rapid cell growth and high temperature, since fis cells grow slower than wild-type cells in r...

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Section: Discussionmentioning

confidence: 96%

Deletion analysis of the fis promoter region in Escherichia coli: antagonistic effects of integration host factor and Fis

et al. 1997

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“…These findings are in agreement with published data on the role of IHF in other systems. For example, expression of algD in Pseudomonas aeruginosa (13,34) and of the E. coli sodA and ilvP G promoters (38,39,44) is regulated two-to fourfold by IHF. In S. flexneri, expression of the structural genes required for invasiveness is dependent upon IHF only in the stationary phase.…”

Section: Discussionmentioning

confidence: 99%

Positive regulation of Shigella flexneri virulence genes by integration host factor

Porter

Dorman

1997

J Bacteriol

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In Shigella flexneri, expression of the plasmid-encoded virulence genes is regulated via a complex cascade involving DNA topology, specific transactivators, and the nucleoid-associated protein H-NS, which represses transcription under inappropriate environmental conditions. We have investigated the involvement of a second nucleoid-associated protein, integration host factor (IHF), in virulence gene expression. We found that transcription of the invasion-specific genes is repressed in a strain harboring an ihfA mutation, particularly on entry into the stationary phase. Expression of the virB gene, whose product is required for the activation of these structural genes, is also enhanced by IHF in the stationary phase. In contrast, the virF gene, which encodes an activator of virB, is stimulated by IHF in both the logarithmic and early stationary phases of growth, as is another virF-regulated gene, icsA. We have identified regions of the virF, virB, and icsA promoters which form IHF-dependent protein-DNA complexes in vitro and have located sequences within these regions with similarity to the consensus IHF binding site. Moreover, results from experiments in which the virF or virB gene was expressed constitutively confirm that IHF has a direct input at the level of both virF and virB transcription. Finally, we provide evidence that at the latter promoter, the primary role of IHF may be to overcome repression by the H-NS protein. To our knowledge, this is the first report of a role for IHF in controlling gene expression in S. flexneri.The facultative intracellular pathogen Shigella flexneri is the causative agent of bacillary dysentery. Its ability to cause disease is dependent upon the presence of a 230-kb plasmid, of which a 31-kb region encodes all proteins required for invasion of host epithelial cells (reviewed in reference 23). Within this region, one DNA strand encodes the Ipa invasins and IcsB, required for inter-and intracellular spreading, while upstream, and transcribed divergently, are the mxi and spa operons, which are responsible for surface presentation and secretion of the invasion proteins by a type III secretion mechanism (2-5, 47, 55) (Fig.

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“…Thus Landy, 1989;Nash, 1990;Pagel et al, 1992). The bacterial integration host factor (IHF) is representative of this class of regulatory proteins.…”

Section: Oxford University Pressmentioning

confidence: 99%

LEF-1 contains an activation domain that stimulates transcription only in a specific context of factor-binding sites.

1993

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Lymphoid enhancer factor 1 (LEF‐1) is a member of the high mobility group (HMG) family of proteins and participates in the regulation of the T cell receptor (TCR) alpha enhancer. We have previously shown that DNA binding by the HMG domain of LEF‐1 induces a sharp bend in the DNA helix. Together with the dependence of LEF‐1 on other factor‐binding sites to regulate gene expression, DNA bending induced by the HMG domain suggested an ‘architectural’ role for LEF‐1. In this study, we performed experiments to distinguish between a model in which the HMG domain is the only functional determinant of LEF‐1 and a model in which additional domains of LEF‐1 are involved in the regulation of gene expression. First, we show that the HMG domain alone is not sufficient to stimulate TCR alpha enhancer function. Second, we replaced the HMG domain of LEF‐1 with the DNA‐binding domain of the bacterial repressor LexA, which binds a specific nucleotide sequence without inducing a sharp bend in the DNA helix. The chimeric LEF‐LexA protein increased the activity of a TCR alpha enhancer in which the LEF‐1‐binding site had been replaced with a LexA recognition sequence. Transcriptional stimulation by LEF‐LexA, however, was less efficient than that observed with endogenous LEF‐1. The LEF‐LexA‐mediated activation of gene expression was dependent upon an amino‐terminal region of LEF‐1 and a specific context of factor‐binding sites in the TCR alpha enhancer. Neither multimerized LexA‐binding sites, nor TCR alpha enhancers with altered spatial arrangements of factor‐binding sites, were functional for regulation by LEF‐LexA. Together, these data suggest that an aminoterminal region in LEF‐1 contributes to the context‐dependent regulation of the TCR alpha enhancer by LEF‐1, presumably by interacting with other enhancer‐bound proteins.

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DNA topology-mediated regulation of transcription initiation from the tandem promoters of the ilvGMEDA operon of Escherichia coli

Cited by 35 publications

References 56 publications

Deletion analysis of the fis promoter region in Escherichia coli: antagonistic effects of integration host factor and Fis

Deletion analysis of the fis promoter region in Escherichia coli: antagonistic effects of integration host factor and Fis

Positive regulation of Shigella flexneri virulence genes by integration host factor

LEF-1 contains an activation domain that stimulates transcription only in a specific context of factor-binding sites.

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