The positive regulator CfaD overcomes the repression mediated by histone-like protein H-NS (H1) in the CFA/I fimbrial operon of Escherichia coli.

Jordi, Bart J.A.M.; Dagberg, Björn; Haan, Louise A.M. de; Hamers, Anja M.; Zeijst, B. A. M. Van Der; Gaastra, Wim; Uhlin, Bernt Eric

doi:10.1002/j.1460-2075.1992.tb05328.x

Cited by 130 publications

(126 citation statements)

References 40 publications

(33 reference statements)

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“…There is accumulating evidence that H-NS distorts DNA, although the nature of this distortion is unclear: H-NS can constrain DNA supercoils in vitro (5), it can act at a distance in vivo (13,17,28), and it generates DNase I-hypersensitive sites on binding (5,13,16). Although proU is simpler than other H-NS-dependent promoters, in that it does not appear to require additional trans-acting factors, there is no a priori reason why similar mechanisms should not operate at many other H-NS-dependent promoters; positive regulators may alter local promoter architecture to overcome H-NS repression (42).…”

Section: Discussionmentioning

confidence: 99%

DNA Binding Is Not Sufficient for H-NS-mediated Repression ofproU Expression

Jordi¹,

Fielder

Burns

et al. 1997

Journal of Biological Chemistry

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H-NS is a major component of bacterial chromatin and influences the expression of many genes. H-NS has beenshown to exhibit a binding preference for certain ATrich curved DNA elements in vitro. In this study we have addressed the factors that determine the specificity of H-NS action in vitro and in vivo. In bandshift studies, H-NS showed a slight binding preference for all curved sequences tested whether GC-based or AT-based; the specific architecture of the curve also influenced H-NS binding. In filter retention assays little difference in affinity could be detected for any sequence tested, including the downstream regulatory element (DRE) a downstream curved DNA element required for H-NS to repress transcription of the Salmonella typhimurium proU operon in vivo. A K d of 1-2 M was estimated for binding of H-NS to each of these sequences. In vivo, the distance between the proU promoter and the DRE, their relative orientations on the face of the DNA helix, and translation of the DRE had no major effect on proU regulation. None of the synthetic curved sequences tested could functionally replace the DRE in vivo. These data show that differential binding to curved DNA cannot account for the specificity of H-NS action in vivo. Furthermore, binding of H-NS to DNA per se is insufficient to repress the proU promoter. Thus, the DRE does not simply act as an H-NS binding site but must have a more specific role in mediating H-NS regulation of proU transcription.

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Section: Discussionmentioning

confidence: 99%

DNA Binding Is Not Sufficient for H-NS-mediated Repression ofproU Expression

Jordi¹,

Fielder

Burns

et al. 1997

Journal of Biological Chemistry

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“…In those cases where the matter has been investigated, the AraC-like protein has been found both to antagonize H-NS repression and to exert a positive influence (albeit a modest one) on The virB regulatory virulence gene in Shigella flexneri and enteroinvasive E. coli Falconi et al (1998); Porter & Dorman (2002) promoter function in the absence of the repressor (Jordi et al, 1992;Murphree et al, 1997). Those AraC-like proteins that derepress and activate thermally responsive virulence genes do not appear to bind chemical ligands; they respond instead to a physical signal (temperature).…”

Section: Arac-like Proteins and H-nsmentioning

confidence: 99%

“…In each case the positive regulator has been shown to require two binding sites, one located upstream and one downstream of the promoter (Jordi et al, 1992;Murphree et al, 1997). The requirement for the downstream site has never been explained adequately (Egan, 2002) and it is tempting to speculate that it is involved in the establishment of an Rns-or CfaD-mediated bridge that protects the promoter from incursion by H-NS.…”

Section: The Leuo Protein: Setting Boundariesmentioning

confidence: 99%

Anti-silencing: overcoming H-NS-mediated repression of transcription in Gram-negative enteric bacteria

2008

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“…However, the signal transduction system encoded by the cblS, cblT, and cblR genes represents a novel, and thus far unique, mechanism for transcriptional regulation of a pilus gene cluster belonging to the CS1 family. The expression of other CS1 family pilus gene clusters is positively regulated by AraC-like proteins, termed Rns or CfaD, which relieve H-NS-mediated gene repression (19,24). The cblS, cblT, and cblR genes are a unique feature of the B. cenocepacia locus, which suggests that they have been acquired and/or employed by the pathway after the emergence of the ancestral CS1 pilus biogenesis locus, encompassing orthologs of cblBACD.…”

Section: Discussionmentioning

confidence: 99%

Genetic Characterization of a Multicomponent Signal Transduction System Controlling the Expression of Cable Pili in Burkholderia cenocepacia

Tomich

Mohr

2004

J Bacteriol

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Cable pili are peritrichous organelles expressed by certain strains of Burkholderia cenocepacia, believed to facilitate colonization of the lower respiratory tract in cystic fibrosis patients. The B. cenocepacia cblBACDS operon encodes the structural and accessory proteins required for the assembly of cable pili, as well as a gene designated cblS, predicted to encode a hybrid sensor kinase protein of bacterial two-component signal transduction systems. In this study we report the identification of two additional genes, designated cblT and cblR, predicted to encode a second hybrid sensor kinase and a response regulator, respectively. Analyses of the deduced amino acid sequences of the cblS and cblT gene products revealed that both putative sensor kinases have transmitter and receiver domains and that the cblT gene product has an additional C-terminal HPt domain. Mutagenesis of the cblS, cblT, or cblR gene led to a block in expression of CblA, the major pilin subunit, and a severe decrease in cblA transcript abundance. Using transcriptional fusion analyses, the decrease in the abundance of the cblA transcript in the cblS, cblT, and cblR mutants was shown to be due to a block in transcription from the cblB-proximal promoter, located upstream of the cblBACDS operon. Furthermore, ectopic expression of either cblS or cblR in wild-type B. cenocepacia strain BC7 led to a significant increase, while ectopic expression of cblT resulted in a dramatic decrease, in abundance of the CblA major pilin and the cblA transcript. Our results demonstrate that the B. cenocepacia cblS, cblT, and cblR genes are essential for cable pilus expression and that their effect is exerted at the level of transcription of the cblBACDS operon. These findings are consistent with the proposed function of the cblSTR gene products as a multicomponent signal transduction pathway controlling the expression of cable pilus biosynthetic genes in B. cenocepacia.

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The positive regulator CfaD overcomes the repression mediated by histone-like protein H-NS (H1) in the CFA/I fimbrial operon of Escherichia coli.

Cited by 130 publications

References 40 publications

DNA Binding Is Not Sufficient for H-NS-mediated Repression ofproU Expression

DNA Binding Is Not Sufficient for H-NS-mediated Repression ofproU Expression

Anti-silencing: overcoming H-NS-mediated repression of transcription in Gram-negative enteric bacteria

Genetic Characterization of a Multicomponent Signal Transduction System Controlling the Expression of Cable Pili in Burkholderia cenocepacia

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