The chromatin-associated protein H-NS alters DNA topology in vitro.

Tupper, A. E.; Owen-Hughes, Tom; Ussery, David W.; Santos, Daniel Silas Veras dos; Ferguson, David; Sidebotham, Julie M.; Hinton, Jay C. D.; Higgins, Claire A.

doi:10.1002/j.1460-2075.1994.tb06256.x

Cited by 198 publications

(186 citation statements)

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“…These architectural changes could involve DNA flexibility (the proU promoter is activated by increased DNA flexibility; 41) and/or DNA looping. 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%

“…Indeed, it may be that curved DNA sequence elements are required for the action of H-NS at all promoters (15)(16)(17). However, for the limited number of DNA curves studied, the increased preference for curved DNA, compared with nonspecific binding to generic DNA, is only a few-fold (5,12,13,18). Furthermore, as curved DNA sequences are found near most promoters, including many promoters that are not responsive to H-NS (for review see Ref.…”

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confidence: 99%

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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%

mentioning

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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“…It has been unclear as to how H-NS binds to such sites, but recently it was demonstrated that H-NS itself can bend DNA and this property could be utilized when H-NS interacts with DNA that is not naturally curved (Spurio et al, 1997). The superhelical status of the DNA does not influence H-NS binding (Spassky et al, 1984;Tupper et al, 1994) and H-NS retains the same ability to repress transcription within the range of superhelical densities normally present in the cell .…”

Section: Dna Bindingmentioning

confidence: 99%

H‐NS: a modulator of environmentally regulated gene expression

Atlung

Ingmer

1997

Molecular Microbiology

453

409

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SummaryH-NS is a small chromatin-associated protein found in enterobacteria. H-NS has affinity for all types of nucleic acids but binds preferentially to intrinsically curved DNA. The major role of H-NS is to modulate the expression of a large number of genes, mostly by negatively affecting transcription. Many of the H-NS-modulated genes are regulated by environmental signals, and expression of most of these genes is positively regulated by specific transcription factors. Therefore one of the purposes of H-NS could be to repress expression of some genes under conditions characteristic of a non-intestinal environment, but allow expression of specific genes in response to certain stimuli in the intestinal environment. The hns gene is autoregulated. In vivo the H-NS to DNA ratio is fairly constant except during cold shock, when it increases threeto fourfold. In this review we propose that only the preferential binding to intrinsically curved DNA plays a role under normal growth conditions, and we discuss the different mechanisms by which H-NS might affect gene expression and how H-NS could be involved in the response to different stress situations. Finally, we summarize the evolutionary and functional relationship between H-NS and the homologous StpA.

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“…Loss of the other major nucleoid-associated proteins, HU and H-NS, results in a decrease (Tanaka et al, 1995;Paull and Johnson, 1995) and an increase ; but see Yasuzawa et al, 1992), respectively, in negative superhelicity in vivo. However, both of these proteins at subsaturating concentrations constrain negative supercoils in vitro (Rouvière-Yaniv et al, 1979;Broyles and Pettijohn, 1986;Tupper et al, 1994). Furthermore, it is known that FIS is a transcriptional regulator of the hupA/hupB and hns promoters (Claret and Rouviè re-Yaniv, 1996;Falconi et al, 1996).…”

Section: Biological Implicationsmentioning

confidence: 99%

FIS modulates growth phase‐dependent topological transitions of DNA in Escherichia coli

Schneider

Travers

Muskhelishvili

1997

Molecular Microbiology

116

104

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SummaryThe Escherichia coli DNA-binding protein FIS serves as a DNA architectural factor in two unrelated enzymatic reactions, the site-specific inversion of DNA and transcriptional activation of stable RNA promoters. In both these processes, FIS facilitates the assembly and dynamic transitions of two structurally distinct nucleoprotein complexes. We have proposed previously that, in these systems, FIS stabilizes writhed DNA microloops by binding at multiple helically phased sites in DNA. However, FIS also binds and bends DNA at many non-specific sites and, at its maximum levels in the early exponential phase, FIS could potentially occupy a considerable part of the E. coli chromosome. Here, we show that fis affects growth phase-specific alterations in the supercoiling level of DNA. Expression of fis accelerates the accumulation of moderately supercoiled plasmids in stationary phase, which are stabilized by FIS after nutritional shift-up. In accordance with such a function, FIS modulates the relaxing and supercoiling activities of topoisomerases in vitro in a way that keeps DNA in a moderately supercoiled state. Our results suggest that the primary role of FIS is to modulate chromosomal dynamics during bacterial growth.

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The chromatin-associated protein H-NS alters DNA topology in vitro.

Cited by 198 publications

References 64 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

H‐NS: a modulator of environmentally regulated gene expression

FIS modulates growth phase‐dependent topological transitions of DNA in Escherichia coli

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