Hla, an<i>E. coli</i>DNA-binding protein which accumulates in stationary phase, strongly compacts DNA<i>in vitro</i>

Spassky, Annick; Rimsky, Sylvie; Garreau, Hervé; Buc, Henri

doi:10.1093/nar/12.13.5321

Cited by 226 publications

(187 citation statements)

References 54 publications

(45 reference statements)

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“…DNA curvature changes significantly in response to altered environmental conditions (19), 2 and it is tempting to postulate that, at simple promoters such as proU, the structure of the DRE itself may act as an "environmental sensor"; environmentally induced changes in DNA configura- 3 it is possible to envisage a mechanism by which H-NS can regulate specific genes in response to different environmental signals. The possibility that environmental signals may directly affect promoter architecture and hence transcription, through influencing the interaction of architectural proteins with DNA, may be an important concept in understanding the environmental regulation of gene expression in bacteria.…”

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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“…minor isoform. All three isoforms bind strongly to DNA (Spassky et al, 1984). The recent unambiguous demonstration that all the isoforms are hns gene products strongly suggests that H-NS undergoes post-translational modification.…”

Section: Figmentioning

confidence: 98%

“…The amount of H-NS present in E. coli cells has been determined using 35 SO 4 labelling and two-dimensional O'Farrel gelelectrophoresis (Spassky et al, 1984). The total amount of H-NS is 14 000 monomers per cell (the sum of the three isoforms).…”

Section: Dna Bindingmentioning

confidence: 99%

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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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“…The major nucleoid-associated protein HU has been shown to constrain negative supercoils by compacting the DNA into nucleosome-like structures (Rouviè re-Yaniv et al, 1979;Broyles and Pettijohn, 1986). Another important protein implicated in the structure of the E. coli nucleoid is H-NS (Varshavsky et al, 1977;Spassky et al, 1984;Higgins et al, 1988; reviewed by Ussery et al, 1994), which binds preferentially to curved DNA (Bracco et al, 1989;Yamada et al, 1990;Zuber et al, 1994) and, when overproduced, results in the condensation of bacterial chromosome (Spurio et al, 1992).…”

Section: Introductionmentioning

confidence: 99%

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

Schneider

Travers

Muskhelishvili

1997

Molecular Microbiology

115

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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Hla, anE. coliDNA-binding protein which accumulates in stationary phase, strongly compacts DNAin vitro

Cited by 226 publications

References 54 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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