The Histone-Like Protein HU Does Not Obstruct Movement of T7 RNA Polymerase in Escherichia coli Cells but Stimulates Its Activity

ABSTRACT In vivo, RNA polymerases (RNAPs) do not transcribe naked DNA but do transcribe protein-associated DNA. Studies with the model enzyme T7 RNAP have shown that, in eukaryotic cells or in vitro, nucleosomes can inhibit both transcription initiation and elongation. We examine here whether the presence of HU, one of the major histone-like proteins in Escherichia coli cells (the genuine milieu for T7 RNAP) affects its activity. An engineered lac operon fused to the T7 late promoter was introduced into the chromosome of T7 RNAP-producing strains that either overexpress HU or lack it. The flows of RNAP that enter and exit this operon were compared with regard to the content of HU. We found that the fraction of T7 RNAP molecules that do not reach the end of the lac operon (ca. 15%) is the same whether the host cells overexpressed HU or lacked it: thus, the enzyme either freely displaces HU or transcribes through it. However, in these cells, the transcript yield was increased when HU is overexpressed and decreased in the hup mutants, presumably reflecting changes in DNA supercoiling. Thus, in contrast to eukaryotic nucleosomes, HU does not impair T7 RNAP activity but has a stimulatory effect. Finally, our results suggest that HU can also influence mRNA stability in vivo.

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A Conserved PapB Family Member, TosR, Regulates Expression of the Uropathogenic Escherichia coli RTX Nonfimbrial Adhesin TosA while Conserved LuxR Family Members TosE and TosF Suppress Motility

Infection and Immunity ◽

10.1128/iai.01608-14 ◽

2014 ◽

Vol 82 (9) ◽

pp. 3644-3656 ◽

Cited By ~ 6

Author(s):

Michael D. Engstrom ◽

Christopher J. Alteri ◽

Harry L. T. Mobley

Keyword(s):

Escherichia Coli ◽

Urinary Tract ◽

Virulence Factors ◽

Upper Urinary Tract ◽

Host Cells ◽

Promoter Regions ◽

Content Type ◽

Tract Infections

ABSTRACTA heterogeneous subset of extraintestinal pathogenicEscherichia coli(ExPEC) strains, referred to as uropathogenicE. coli(UPEC), causes most uncomplicated urinary tract infections. However, no core set of virulence factors exists among UPEC strains. Instead, the focus of the analysis of urovirulence has shifted to studying broad classes of virulence factors and the interactions between them. For example, the RTX nonfimbrial adhesin TosA mediates adherence to host cells derived from the upper urinary tract. The associatedtosoperon is well expressedin vivobut poorly expressedin vitroand encodes TosCBD, a predicted type 1 secretion system. TosR and TosEF are PapB and LuxR family transcription factors, respectively; however, no role has been assigned to these potential regulators. Thus, the focus of this study was to determine how TosR and TosEF regulatetosAand affect the reciprocal expression of adhesins and flagella. Among a collection of sequenced UPEC strains, 32% (101/317) were found to encode TosA, and nearly all strains (91% [92/101]) simultaneously carried the putative regulatory genes. Deletion oftosRalleviatestosArepression. Thetospromoter was localized upstream oftosRusing transcriptional fusions of putative promoter regions withlacZ. TosR binds to this region, affecting a gel shift. A 100-bp fragment 220 to 319 bp upstream oftosRinhibits binding, suggesting localization of the TosR binding site. TosEF, on the other hand, downmodulate motility when overexpressed by preventing the expression offliC, encoding flagellin. Deletion oftosEFincreased motility. Thus, we present an additional example of the reciprocal control of adherence and motility.

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Interactions of the Antizyme AtoC with Regulatory Elements of the Escherichia coli atoDAEB Operon

Journal of Bacteriology ◽

10.1128/jb.00214-07 ◽

2007 ◽

Vol 189 (17) ◽

pp. 6324-6332 ◽

Cited By ~ 21

Author(s):

Meropi K. Matta ◽

Efthimia E. Lioliou ◽

Cynthia H. Panagiotidis ◽

Dimitrios A. Kyriakidis ◽

Christos A. Panagiotidis

Keyword(s):

Escherichia Coli ◽

Transcription Initiation ◽

Response Regulator ◽

Regulatory Elements ◽

Initiation Site ◽

Integration Host Factor ◽

Chemical Mutagenesis ◽

Dual Function

ABSTRACT AtoC has a dual function as both an antizyme, the posttranslational inhibitor of polyamine biosynthetic enzymes, and the transcriptional regulator of genes involved in short-chain fatty acid catabolism (the atoDAEB operon). We have previously shown that AtoC is the response regulator of the AtoS-AtoC two-component signal transduction system that activates atoDAEB when Escherichia coli is exposed to acetoacetate. Here, we show that the same cis elements control both promoter inducibility and AtoC binding. Chromatin immunoprecipitation experiments confirmed the acetoacetate-inducible binding of AtoC to the predicted DNA region in vivo. DNase I protection footprinting analysis revealed that AtoC binds two 20-bp stretches, constituting an inverted palindrome, that are located at −146 to −107 relative to the transcription initiation site. Analyses of promoter mutants obtained by in vitro chemical mutagenesis of the atoDAEB promoter verified both the importance of AtoC binding for the inducibility of the promoter by acetoacetate and the σ54 dependence of atoDAEB expression. The integration host factor was also identified as a critical component of the AtoC-mediated induction of atoDAEB.

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Role of F1C Fimbriae, Flagella, and Secreted Bacterial Components in the Inhibitory Effect of Probiotic Escherichia coli Nissle 1917 on Atypical Enteropathogenic E. coli Infection

Infection and Immunity ◽

10.1128/iai.01431-13 ◽

2014 ◽

Vol 82 (5) ◽

pp. 1801-1812 ◽

Cited By ~ 23

Author(s):

Sylvia Kleta ◽

Marcel Nordhoff ◽

Karsten Tedin ◽

Lothar H. Wieler ◽

Rafal Kolenda ◽

...

Keyword(s):

Escherichia Coli ◽

Molecular Mechanisms ◽

Inhibitory Effect ◽

Host Cells ◽

Single Infection ◽

Content Type ◽

E Coli ◽

Initial Adhesion

ABSTRACTEnteropathogenicEscherichia coli(EPEC) is recognized as an important intestinal pathogen that frequently causes acute and persistent diarrhea in humans and animals. The use of probiotic bacteria to prevent diarrhea is gaining increasing interest. The probioticE. colistrain Nissle 1917 (EcN) is known to be effective in the treatment of several gastrointestinal disorders. While bothin vitroandin vivostudies have described strong inhibitory effects of EcN on enteropathogenic bacteria, including pathogenicE. coli, the underlying molecular mechanisms remain largely unknown. In this study, we examined the inhibitory effect of EcN on infections of porcine intestinal epithelial cells with atypical enteropathogenicE. coli(aEPEC) with respect to single infection steps, including adhesion, microcolony formation, and the attaching and effacing phenotype. We show that EcN drastically reduced the infection efficiencies of aEPEC by inhibiting bacterial adhesion and growth of microcolonies, but not the attaching and effacing of adherent bacteria. The inhibitory effect correlated with EcN adhesion capacities and was predominantly mediated by F1C fimbriae, but also by H1 flagella, which served as bridges between EcN cells. Furthermore, EcN seemed to interfere with the initial adhesion of aEPEC to host cells by secretion of inhibitory components. These components do not appear to be specific to EcN, but we propose that the strong adhesion capacities enable EcN to secrete sufficient local concentrations of the inhibitory factors. The results of this study are consistent with a mode of action whereby EcN inhibits secretion of virulence-associated proteins of EPEC, but not their expression.

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A DNA Vaccine Encoding the Enterohemorragic Escherichia coli Shiga-Like Toxin 2 A2 and B Subunits Confers Protective Immunity to Shiga Toxin Challenge in the Murine Model

Clinical and Vaccine Immunology ◽

10.1128/cvi.00328-08 ◽

2009 ◽

Vol 16 (5) ◽

pp. 712-718 ◽

Cited By ~ 25

Author(s):

Leticia V. Bentancor ◽

Marcos Bilen ◽

Romina J. Fernández Brando ◽

María Victoria Ramos ◽

Luis C. S. Ferreira ◽

...

Keyword(s):

Escherichia Coli ◽

Dna Vaccine ◽

Protective Immunity ◽

Host Cells ◽

Therapeutic Interventions ◽

28S Rrna ◽

A Subunit ◽

B Subunits

ABSTRACT Production of verocytotoxin or Shiga-like toxin (Stx), particularly Stx2, is the basis of hemolytic uremic syndrome, a frequently lethal outcome for subjects infected with Stx2-producing enterohemorrhagic Escherichia coli (EHEC) strains. The toxin is formed by a single A subunit, which promotes protein synthesis inhibition in eukaryotic cells, and five B subunits, which bind to globotriaosylceramide at the surface of host cells. Host enzymes cleave the A subunit into the A1 peptide, endowed with N-glycosidase activity to the 28S rRNA, and the A2 peptide, which confers stability to the B pentamer. We report the construction of a DNA vaccine (pStx2ΔAB) that expresses a nontoxic Stx2 mutated form consisting of the last 32 amino acids of the A2 sequence and the complete B subunit as two nonfused polypeptides. Immunization trials carried out with the DNA vaccine in BALB/c mice, alone or in combination with another DNA vaccine encoding granulocyte-macrophage colony-stimulating factor, resulted in systemic Stx-specific antibody responses targeting both A and B subunits of the native Stx2. Moreover, anti-Stx2 antibodies raised in mice immunized with pStx2ΔAB showed toxin neutralization activity in vitro and, more importantly, conferred partial protection to Stx2 challenge in vivo. The present vector represents the second DNA vaccine so far reported to induce protective immunity to Stx2 and may contribute, either alone or in combination with other procedures, to the development of prophylactic or therapeutic interventions aiming to ameliorate EHEC infection-associated sequelae.

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Structure of hibernating ribosomes studied by cryoelectron tomography in vitro and in situ

The Journal of Cell Biology ◽

10.1083/jcb.201005007 ◽

2010 ◽

Vol 190 (4) ◽

pp. 613-621 ◽

Cited By ~ 67

Author(s):

Julio O. Ortiz ◽

Florian Brandt ◽

Valério R.F. Matias ◽

Lau Sennels ◽

Juri Rappsilber ◽

...

Keyword(s):

Escherichia Coli ◽

Stress Response ◽

Spatial Organization ◽

Three Dimensional ◽

E Coli ◽

Escherichia Coli Cells ◽

Three Dimensional Configuration

Ribosomes arranged in pairs (100S) have been related with nutritional stress response and are believed to represent a “hibernation state.” Several proteins have been identified that are associated with 100S ribosomes but their spatial organization has hitherto not been characterized. We have used cryoelectron tomography to reveal the three-dimensional configuration of 100S ribosomes isolated from starved Escherichia coli cells and we have described their mode of interaction. In situ studies with intact E. coli cells allowed us to demonstrate that 100S ribosomes do exist in vivo and represent an easily reversible state of quiescence; they readily vanish when the growth medium is replenished.

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Stimulation of the λ p R promoter by Escherichia coli SeqA protein requires downstream GATC sequences and involves late stages of transcription initiation

Microbiology ◽

10.1099/mic.0.29110-0 ◽

2006 ◽

Vol 152 (10) ◽

pp. 2985-2992 ◽

Cited By ~ 7

Author(s):

Robert Łyżeń ◽

Grzegorz Wȩgrzyn ◽

Alicja Wȩgrzyn ◽

Agnieszka Szalewska-Pałasz

Keyword(s):

Escherichia Coli ◽

Transcription Initiation ◽

Negative Regulator ◽

Regulation Of Transcription ◽

Chromosomal Dna ◽

Transcription Activator ◽

Transcription Analysis ◽

Stimulation Of

Escherichia coli SeqA protein is a major negative regulator of chromosomal DNA replication acting by sequestration, and thus inactivation, of newly formed oriC regions. However, other activities of this protein have been discovered recently, one of which is regulation of transcription. SeqA has been demonstrated to be a specific transcription factor acting at bacteriophage λ promoters p I, p aQ and p R. While SeqA-mediated stimulation of p I and p aQ occurs by facilitating functions of another transcription activator protein, cII, a mechanism for stimulation of p R remains largely unknown. Here, it has been demonstrated that two GATC sequences, located 82 and 105 bp downstream of the p R transcription start site, are necessary for this stimulation both in vivo and in vitro. SeqA-mediated activation of p R was as effective on a linear DNA template as on a supercoiled one, indicating that alterations in DNA topology are not likely to facilitate the SeqA effect. In vitro transcription analysis demonstrated that the most important regulatory effect of SeqA in p R transcription occurs after open complex formation, namely during promoter clearance. SeqA did not influence the appearance and level of abortive transcripts or the pausing during transcription elongation. Interestingly, SeqA is one of few known prokaryotic transcription factors which bind downstream of the regulated promoter and still act as transcription activators.

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Thymine at —5 Is Crucial for cpc Promoter Activity of Synechocystis sp. Strain PCC 6714

Journal of Bacteriology ◽

10.1128/jb.185.21.6477-6480.2003 ◽

2003 ◽

Vol 185 (21) ◽

pp. 6477-6480 ◽

Cited By ~ 16

Author(s):

Masahiko Imashimizu ◽

Shoko Fujiwara ◽

Ryohei Tanigawa ◽

Kan Tanaka ◽

Takatsugu Hirokawa ◽

...

Keyword(s):

Escherichia Coli ◽

Rna Polymerase ◽

Transcription Initiation ◽

Promoter Activity ◽

Initiation Site ◽

Pcc 7942 ◽

Rna Polymerase Promoter ◽

Synechocystis Sp

ABSTRACT The levels of transcripts of the cpc operon were highly reduced in a PD-1 mutant of cyanobacterium Synechocystis sp. strain PCC 6714. This was due to a substitution of C for T that occurred at 5 bp upstream of the transcription initiation site of the cpc operon. Any substitution for T at the −5 position drastically reduced both in vivo and in vitro promoter activity in cyanobacterium Synechococcus sp. strain PCC 7942 but not the in vivo activity in Escherichia coli. This suggests that the requirement of −5T appears to be specific for a cyanobacterial RNA polymerase-promoter combination.

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Heat-Labile Enterotoxin Promotes Escherichia coli Adherence to Intestinal Epithelial Cells

Journal of Bacteriology ◽

10.1128/jb.00822-08 ◽

2008 ◽

Vol 191 (1) ◽

pp. 178-186 ◽

Cited By ~ 68

Author(s):

Amber M. Johnson ◽

Radhey S. Kaushik ◽

David H. Francis ◽

James M. Fleckenstein ◽

Philip R. Hardwidge

Keyword(s):

Escherichia Coli ◽

Surface Expression ◽

Host Cells ◽

Intestinal Epithelial ◽

Host Interactions ◽

Heat Labile ◽

Vitro Model ◽

Bacterial Sensing

ABSTRACT Given recent evidence suggesting that the heat-labile enterotoxin (LT) provides a colonization advantage for enterotoxigenic Escherichia coli (ETEC) in vivo, we hypothesized that LT preconditions the host intestinal epithelium for ETEC adherence. To test this hypothesis, we used an in vitro model of ETEC adherence to examine the role of LT in promoting bacterium-host interactions. We present data demonstrating that elaboration of LT promotes a significant increase in E. coli adherence. This phenotype is primarily dependent on the inherent ADP-ribosylation activity of this toxin, with a secondary role observed for the receptor-binding LT-B subunit. Rp-3′,5′-cyclic AMP (cAMP), an inhibitor of protein kinase A, was sufficient to abrogate LT's ability to promote subsequent bacterial adherence. Increased adherence was not due to changes in the surface expression of the host receptor for the K88ac adhesin. Evidence is also presented for a role for bacterial sensing of host-derived cAMP in promoting adherence to host cells.

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In Vitro Labeling Strategies for Identifying Primary Neural Tissue and a Neuronal Cell Line after Transplantation in the Cns

Cell Transplantation ◽

10.1177/096368979300200207 ◽

1993 ◽

Vol 2 (2) ◽

pp. 131-149 ◽

Cited By ~ 51

Author(s):

Stephen M. Onifer ◽

Linda A. White ◽

Scott R. Whittemore ◽

Vicky R. Holets

Keyword(s):

Escherichia Coli ◽

Cell Line ◽

Neuronal Cell ◽

Fluorescein Isothiocyanate ◽

Initial Step ◽

Host Cells ◽

Lacz Gene ◽

Raphe Neurons

Potential labels for identifying embryonic raphe neurons and a clonal, neuronally differentiating, raphe-derived cell line, RN33B, in CNS transplantation studies were tested by first characterizing the labels in vitro. The labels that were tested included 4,6-diamidino-2-phenylindole hydrochloride, 1,1′-dioctadecyl-3,3,3′-tetramethylindocarbocyanine perchlorate, the Escherichia coli lacZ gene, Fast Blue, Fluoro-Gold, fluorescein-conjugated latex microspheres, fluorescein isothiocyanate-conjugated or nonconjugated Phaseolus vulgaris leucoagglutinin, methyl o-(6-amino-3′-imino-3H-xanthen-9-yl) benzoate monohydrochloride, or tetanus toxin C fragment. Subsequently, the optimal in vitro labels for embryonic raphe neurons and for RN33B cells were characterized in vivo after CNS transplantation. In vitro, 1,1-dioctadecyl-3,3,3′-tetramethylindocarbocyanine perchlorate (DiI) optimally labeled embryonic neurons. The Escherichia coli lacZ gene optimally labeled RN33B cells. Most labels were rapidly diluted in cultures of embryonic astrocytes and proliferating RN33B cells. Some labels were toxic and were often retained in cellular debris. In vivo, DiI was visualized in transplanted, DiI-labeled raphe neurons, but not in astrocytes up to 1 mo posttransplant. DiI-labeled host cells were seen after transplantation of lysed, DiI-labeled cells. β-Galactosidase was visualized in transplanted, Escherichia coli lacZ gene-labeled RN33B cells after 15 days in vivo. No β-galactosidase was seen in host cells after transplantation of lysed, lacZ-labeled RN33B cells. The results demonstrate that labels for use in CNS transplantation studies should be optimized for the specific population of donor cells under study, with the initial step being characterization in vitro followed by in vivo analysis. Appropriate controls for false-positive labeling of host cells should always be assessed.

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