Characterization of the Opposing Roles of H-NS and TraJ in Transcriptional Regulation of the F-Plasmid
            <i>tra</i>
            Operon

Will, William R.; Frost, Laura S.

doi:10.1128/jb.188.2.507-514.2006

Cited by 39 publications

(49 citation statements)

References 62 publications

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“…However, the proposed role for F TraJ in simply antagonizing H-NS at the P Y promoter seems to be only partially true for R1. Deletion of hns led to a 10-fold increase in mating efficiency of plasmid R1; in contrast Will & Frost reported a 10 4 -fold increase of mating efficiency of F (Will & Frost, 2006), suggesting that H-NS mediated silencing is more effective in that case. Since F TraJ is not subject to FinOP regulation due to a disruption of finO by IS3 (Cheah & Skurray, 1986), higher TraJ levels and thus, compared with R1 and other repressed plasmids, higher transfer gene expression are observed throughout the growth cycle.…”

Section: Silencing and Counter-silencingmentioning

confidence: 89%

“…1). We therefore set up experiments to elucidate whether regulation of tra gene expression at the P Y promoter in the case of the naturally repressed plasmid R1 displays similar characteristics to those found for the F plasmid (Will & Frost, 2006;Will et al, 2004).…”

Section: Discussionmentioning

confidence: 99%

“…For the F plasmid it has been recently proposed that TraJ does not act as a classical transcriptional activator but rather counteracts H-NS mediated repression and thereby activates transcription (Will & Frost, 2006;Will et al, 2004). In R1, H-NS is involved in silencing the P Y promoter and there are additional binding sites for H-NS in the P J and P M promoter regions, the latter overlapping oriT; in addition we could demonstrate direct binding of H-NS to P Y DNA by EMSA and DNase I footprinting (unpublished observations).…”

Section: Silencing and Counter-silencingmentioning

confidence: 99%

“…1) and depends on the plasmid encoded TraJ protein and on the host encoded two-component response-regulator ArcA as was shown for plasmids F, R1, R100 and pSLT (Camacho & Casadesú s, 2002;Serna et al, 2010;Silverman et al, 1991;Strohmaier et al, 1998;Taki et al, 1998). It has been proposed that TraJ F acts as a de-silencing protein that clears the P Y promoter from the nucleoid associated protein H-NS and thereby enables access of RNA polymerase (Will & Frost, 2006). To the best of our knowledge, no information about the role of H-NS is currently available for any of the other plasmids carrying F-like conjugation modules.…”

Section: Introductionmentioning

confidence: 99%

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Silencing and activating type IV secretion genes of the F-like conjugative resistance plasmid R1

et al. 2013

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Expression of DNA transfer (tra) genes of F-type conjugative plasmids is required for the assembly of a functional type IV secretion machinery and subsequent plasmid DNA transfer from donor to recipient cells. Transcription of tra genes depends on the activation of a single promoter, designated P Y , by the plasmid encoded TraJ protein. We here determine plasmid specificity of TraJ proteins from various subgroups of F-like plasmids and find that plasmid R1 conjugation and P Y promoter activation can be achieved only by its cognate activator and by TraJ of the Salmonella plasmid pSLT and not by F or R100 TraJ proteins. In addition, we characterize the P Y promoter of plasmid R1. We show that TraJ binds to P Y DNA in vivo and that H-NS acts as a silencer of the P Y promoter. In the natural plasmid context, H-NS silences transfer gene expression and horizontal plasmid DNA transfer. In contrast to what was found for the F plasmid, lack of H-NS did not abolish the requirement for ArcA and TraJ to reach full tra gene expression and DNA transfer activity. We propose that, besides a passive de-silencing activity, both ArcA and TraJ play a direct role in synergistically stimulating tra operon transcription and subsequent DNA transfer.

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Section: Silencing and Counter-silencingmentioning

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Section: Silencing and Counter-silencingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Silencing and activating type IV secretion genes of the F-like conjugative resistance plasmid R1

et al. 2013

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“…The importance of H-NS in regulating horizontal gene transfer is not limited to pathogenesis. The regulatory protein TraJ counter-silences H-NS repression of the tra genes in the F plasmid of E. coli but is dispensable for conjugal transfer in an hns mutant [54], demonstrating that H-NS can limit plasmid mobilization. Some plasmids such as the Salmonella plasmid R27 carry their own H-NS-like protein (Sfh, in the case of R27) that appears to prevent detrimental consequences of H-NS titration by AT-rich sequences [55•] and thereby allow the recipient cell to tolerate the plasmid.…”

Section: Counter-silencing Of H-ns and Its Functional Consequencesmentioning

confidence: 99%

New insights into transcriptional regulation by H-NS

Fang

Rimsky

2008

Current Opinion in Microbiology

188

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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Bacterial Chromatin

2010

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this work may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission from the Publisher, with the exception of any material supplied specifically for the purpose of being entered and executed on a computer system, for exclusive use by the purchaser of the work.Cover illustration: H-NS-DNA complex visualized using scanning force microscopy (Courtesy of R.T. Dame)Printed on acid-free paper Springer is part of Springer Science+Business Media (www.springer.com) v PrefaceThe birth and the development of molecular biology and, subsequently, of genetic engineering and biotechnology cannot be separated from the advancements in our knowledge of the genetics, biochemistry and physiology of bacteria and bacteriophages. Also most of the tools employed nowadays by biotechnologists are of bacterial (or bacteriophage) origin and the playground for most of the DNA manipulations still remains within bacteria. The relative simplicity of the bacterial cell, the short generation times, the well defined and inexpensive culturing conditions which characterize bacteria and the auto-catalytic process whereby a wealth of in-depth information has been accumulated throughout the years have significantly contributed to generate a large number of knowledge-based, reliable and exploitable biological systems.The subtle relationships between phages and their hosts have produced a large amount of information and allowed the identification and characterization of a number of components which play essential roles in fundamental biological processes such as DNA duplication, recombination, transcription and translation. For instance, to remain within the topic of this book, two important players in the organization of the nucleoid, FIS and IHF, have been discovered in this way. Indeed, it is difficult to find a single fundamental biological process whose structural and functional aspects are better known than in bacteria.However, a notable exception is represented by the physical and functional organization of the bacterial genome. Although some bacteria contain more than one chromosome and some chromosomes are known to be linear, the majority of bacterial cells contain a single circular chromosome. The chromosome of Escherichia coli consists of about 4.6 million bp corresponding to a fully extended circumference of about 1.6 mm and rapidly growing bacteria may contain up to almost four genomic equivalents. Thus, the need for compaction of this genetic material to fit within an approximately 500-fold smaller volume is obvious; likewise, also clear is the need for a dynamic "chromatin" structure capable of undergoing rapidly all kinds of vital transactions to respond promptly to different types of environmental cues, changes and stresses with focused and/or global reprogramming of gene expression. All this happens within one or a few ill-defined structures called "nucleoids" where the cellular DNA is localized.The ...

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Characterization of the Opposing Roles of H-NS and TraJ in Transcriptional Regulation of the F-Plasmid tra Operon

Cited by 39 publications

References 62 publications

Silencing and activating type IV secretion genes of the F-like conjugative resistance plasmid R1

Silencing and activating type IV secretion genes of the F-like conjugative resistance plasmid R1

New insights into transcriptional regulation by H-NS

Bacterial Chromatin

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