Environmental Control of the In vivo Oligomerization of Nucleoid Protein H-NS

Stella, Stefano; Falconi, Maurizio; Lammi, M.; Gualerzi, Claudio O.; Pon, Cynthia L.

doi:10.1016/j.jmb.2005.10.034

Cited by 48 publications

(32 citation statements)

References 30 publications

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“…Interestingly, another recent study analyzing H-NS structure and function in response to temperature concluded that H-NS tetramerization and activity is actually higher at elevated temperatures (Stella et al 2006). Chimeric molecules were constructed whereby the Nterminal oligomerization and linker domains of H-NS were fused to the DNA-binding domains of phage repressors.…”

Section: Functions Of H-nsmentioning

confidence: 99%

Silencing of xenogeneic DNA by H-NS—facilitation of lateral gene transfer in bacteria by a defense system that recognizes foreign DNA

Navarre¹,

McClelland²,

Libby³

et al. 2007

Genes Dev.

270

261

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Lateral gene transfer has played a prominent role in bacterial evolution, but the mechanisms allowing bacteria to tolerate the acquisition of foreign DNA have been incompletely defined. Recent studies show that H-NS, an abundant nucleoid-associated protein in enteric bacteria and related species, can recognize and selectively silence the expression of foreign DNA with higher adenine and thymine content relative to the resident genome, a property that has made this molecule an almost universal regulator of virulence determinants in enteric bacteria. These and other recent findings challenge the ideas that curvature is the primary determinant recognized by H-NS and that activation of H-NS-silenced genes in response to environmental conditions occurs through a change in the structure of H-NS itself. Derepression of H-NS-silenced genes can occur at specific promoters by several mechanisms including competition with sequence-specific DNA-binding proteins, thereby enabling the regulated expression of foreign genes. The possibility that microorganisms maintain and exploit their characteristic genomic GC ratios for the purpose of self/non-self-discrimination is discussed.

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Section: Functions Of H-nsmentioning

confidence: 99%

Silencing of xenogeneic DNA by H-NS—facilitation of lateral gene transfer in bacteria by a defense system that recognizes foreign DNA

Navarre¹,

McClelland²,

Libby³

et al. 2007

Genes Dev.

270

261

View full text Add to dashboard Cite

show abstract

“…Thus, temperature-mediated changes in DNA supercoiling and hence in DNA flexibility may affect the ability of H-NS to modulate expression of certain genes or operons (Falconi et al, 1998;Madrid et al, 2002). In addition to indirect effects on DNA, temperature and/or other factors may also influence the ability of H-NS itself to dimerize/oligomerize and to facilitate the interaction with DNA (Ono et al, 2005;Stella et al, 2006). …”

Section: Introductionmentioning

confidence: 99%

A global modulatory role for the Yersinia enterocolitica H-NS protein

et al. 2008

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“…However, a large number of H-NS-repressed genes remain repressed at 37°C, suggesting that a simple effect of temperature on H-NS multimerization or DNA binding cannot account for the temperaturedependent derepression of a subset of genes. Moreover, H-NS oligomerization has been reported to be higher at 37°C than 25°C [18] and uninfluenced by further temperature increases to 48°C or pH variation between 4.0 and 9.0. Similarly, while H-NS represses the transcription of a number of osmoregulated genes [14], many H-NS-silenced genes are unaffected by changes in osmolarity.…”

mentioning

confidence: 99%

New insights into transcriptional regulation by H-NS

Fang

Rimsky

2008

Current Opinion in Microbiology

186

173

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H-NS, a nucleoid-associated DNA-binding protein of enteric bacteria, was discovered thirty-five years ago and subsequently found to exert widespread and highly pleiotropic effects on gene regulation. H-NS binds to high-affinity sites and spreads along adjacent AT-rich DNA to silence transcription. Preferential binding to sequences with higher AT-content than the resident genome allows H-NS to repress the expression of foreign DNA in a process known as "xenogeneic silencing." Counter-silencing by a variety of mechanisms facilitates the evolutionary acquisition of horizontally transferred genes and their integration into pre-existing regulatory networks. This review will highlight recent insights into the mechanism and biological importance of H-NS-DNA interactions. H-NS--A Nucleoid ProteinH-NS is an abundant DNA-binding protein implicated in the organization of the bacterial chromosome [1]. H-NS and other nucleoid-associated proteins can affect DNA topology at specific loci, thereby modulating gene transcription. Binding by these proteins is proposed to selectively direct supercoiling effects to promoters [2•]. Mutation of hns alters the responsiveness of transcription to changes in DNA superhelicity. Regulatory effects of supercoiling are linked to metabolic and environmental conditions. Thus, H-NS has been viewed as a nucleoid structuring protein with global effects on gene expression [3].H-NS exists primarily as a dimer at low concentrations but can multimerize into higher order complexes [4,5] that form bridges between adjacent DNA helices [6]. Optical tweezers have been used to demonstrate that H-NS dimers or multimers can simultaneously interact with separate DNA binding sites [7••]. H-NS-coated DNA is not self-interactive, suggesting that dimerization or oligomerization must precede DNA binding for bridging to occur. Force measurements suggest that transcription barriers created by H-NS binding are weak (∼7 pN) and readily overcome, so that H-NS oligomers pose only a relative barrier to translocating RNA polymerase. DNA bridging is a conserved feature of H-NS homologs found in most gram-negative bacteria [8] that appears to constrain large DNA loops [9••] and helps to account for the effects of H-NS on transcription. However, it must be noted that the relationship between bridging as a general effect and the silencing of specific promoters is not yet clear.H-NS is more appropriately viewed as a determinant of chromosomal architecture rather than as a general structural component. The analysis of nucleoids treated with urea suggests that *Corresponding Author : Tel 206-275-0966, Fax 206-616-1575, e-mail : fcfang@u.washington.edu. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production proce...

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Environmental Control of the In vivo Oligomerization of Nucleoid Protein H-NS

Cited by 48 publications

References 30 publications

Silencing of xenogeneic DNA by H-NS—facilitation of lateral gene transfer in bacteria by a defense system that recognizes foreign DNA

Silencing of xenogeneic DNA by H-NS—facilitation of lateral gene transfer in bacteria by a defense system that recognizes foreign DNA

A global modulatory role for the Yersinia enterocolitica H-NS protein

New insights into transcriptional regulation by H-NS

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