scholarly journals Cryo soft X-ray tomography to explore Escherichia coli nucleoid remodelling by Hfq master regulator

2021 ◽  
Author(s):  
Antoine Cossa ◽  
Sylvain Trépout ◽  
Frank Wien ◽  
Etienne Le Brun ◽  
Florian Turbant ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Growth Phase ◽  
Noncoding Rna ◽  
Stationary Growth Phase ◽  
Transcriptional Level ◽  
X Ray ◽  
Small Noncoding Rna ◽  
Associated Proteins ◽  
Post Transcriptional Regulation

Bacterial chromosomic DNA is packed within a membrane-less structure, the nucleoid, thanks to proteins called Nucleoid Associated Proteins (NAPs). The NAP composition of the nucleoid varies during the bacterial life cycle and is growth phase-dependent. Among these NAPs, Hfq is one of the most intriguing as it plays both direct and indirect roles on DNA structure. Indeed, Hfq is best known to mediate post-transcriptional regulation by using small noncoding RNA (sRNA). Although Hfq presence in the nucleoid has been demonstrated for years, its precise role is still unclear. Recently, it has been shown in vitro that Hfq belongs to the bridging family of NAPs. Its bridging mechanism relies on the formation of the amyloid-like structure of Hfq C-terminal region. Here, using cryo soft X-ray tomography imaging of native unlabelled cells and using a semi-automatic analysis and segmentation procedure, we show that Hfq significantly remodels the Escherichia coli nucleoid, especially during the stationary growth phase. Hfq influences both nucleoid volume and absorbance. Hfq cumulates direct effects and indirect effects due to sRNA-based regulation of other NAPs. Taken together, our findings reveal a new role for this protein in nucleoid remodelling that may serve in response to stress conditions and in adapting to changing environments. This implies that Hfq regulates nucleoid compaction directly via its interaction with DNA, but also at the post-transcriptional level via its interaction with RNA.

scholarly journals σE Regulates and Is Regulated by a Small RNA in Escherichia coli

2007 ◽  
Vol 189 (11) ◽  
pp. 4243-4256 ◽  
Author(s):  
Karl M. Thompson ◽  
Virgil A. Rhodius ◽  
Susan Gottesman
Keyword(s):  
Escherichia Coli ◽  
Small Rnas ◽  
Noncoding Rna ◽  
Response Regulator ◽  
Heterologous Promoter ◽  
Genomic Libraries ◽  
Multicopy Suppressors ◽  
Intergenic Regions ◽  
Transposon Mutants

ABSTRACT RybB is a small, Hfq-binding noncoding RNA originally identified in a screen of conserved intergenic regions in Escherichia coli. Fusions of the rybB promoter to lacZ were used to screen plasmid genomic libraries and genomic transposon mutants for regulators of rybB expression. A number of plasmids, including some carrying rybB, negatively regulated the fusion. An insertion in the rep helicase and one upstream of dnaK decreased expression of the fusion. Multicopy suppressors of these insertions led to identification of two plasmids that stimulated the fusion. One contained the gene for the response regulator OmpR; the second contained mipA, encoding a murein hydrolase. The involvement of MipA and OmpR in cell surface synthesis suggested that the rybB promoter might be dependent on σE. The sequence upstream of the +1 of rybB contains a consensus σE promoter. The activity of rybB-lacZ was increased in cells lacking the RseA anti-sigma factor and when σE was overproduced from a heterologous promoter. The activity of rybB-lacZ and the detection of RybB were totally abolished in an rpoE-null strain. In vitro, σE efficiently transcribes from this promoter. Both a rybB mutation and an hfq mutation significantly increased expression of both rybB-lacZ and rpoE-lacZ fusions, consistent with negative regulation of the σE response by RybB and other small RNAs. Based on the plasmid screens, NsrR, a repressor sensitive to nitric oxide, was also found to negatively regulate σE-dependent promoters in an RseA-independent fashion.

scholarly journals Noncoding RNAs in Cancer Medicine

2006 ◽  
Vol 2006 ◽  
pp. 1-8 ◽  
Author(s):  
Laura Cerchia ◽  
Vittorio De Franciscis
Keyword(s):  
Noncoding Rna ◽  
High Specificity ◽  
Affinity Ligands ◽  
Small Noncoding Rna ◽  
Innovative Methods ◽  
Attractive Candidate ◽  
Associated Proteins ◽  
Cell Growth And Differentiation ◽  
Cancer Medicine ◽  
Regulatory Rnas

Several signalling proteins involved in cell growth and differentiation represent attractive candidate targets for cancer diagnosis and/or therapy since they can act as oncogenes. Because of their high specificity and low immunogeneicity, using artificial small noncoding RNA (ncRNAs) as therapeutics has recently become a highly promising and rapidly expanding field of interest. Indeed, ncRNAs may either interfere with RNA transcription, stability, translation or directly hamper the function of the targets by binding to their surface. The recent finding that the expression of several genes is under the control of small single-stranded regulatory RNAs, including miRNAs, makes these genes as appropriate targets for ncRNA gene silencing. Furthermore, another class of small ncRNA, aptamers, act as high-affinity ligands and potential antagonists of disease-associated proteins. We will review here the recent and innovative methods that have been developed and the possible applications of ncRNAs as inhibitors or tracers in cancer medicine.

scholarly journals Growth Phase-Dependent Regulation and Stringent Control of fis Are Conserved Processes in Enteric Bacteria and Involve a Single Promoter (fis P) in Escherichia coli

2004 ◽  
Vol 186 (1) ◽  
pp. 122-135 ◽  
Author(s):  
Prabhat Mallik ◽  
Timothy S. Pratt ◽  
Michael B. Beach ◽  
Meranda D. Bradley ◽  
Jayanthi Undamatla ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Growth Phase ◽  
Primer Extension ◽  
E Coli ◽  
Stringent Control ◽  
Regulatory Processes ◽  
Nutritional Environment ◽  
Nuclease Mapping ◽  
Single Promoter

ABSTRACT The intracellular concentration of the Escherichia coli factor for inversion stimulation (Fis), a global regulator of transcription and a facilitator of certain site-specific DNA recombination events, varies substantially in response to changes in the nutritional environment and growth phase. Under conditions of nutritional upshift, fis is transiently expressed at very high levels, whereas under induced starvation conditions, fis is repressed by stringent control. We show that both of these regulatory processes operate on the chromosomal fis genes of the enterobacteria Klebsiella pneumoniae, Serratia marcescens, Erwinia carotovora, and Proteus vulgaris, strongly suggesting that the physiological role of Fis is closely tied to its transcriptional regulation in response to the nutritional environment. These transcriptional regulatory processes were previously shown to involve a single promoter (fis P) preceding the fis operon in E. coli. Recent work challenged this notion by presenting evidence from primer extension assays which appeared to indicate that there are multiple promoters upstream of fis P that contribute significantly to the expression and regulation of fis in E. coli. Thus, a rigorous analysis of the fis promoter region was conducted to assess the contribution of such additional promoters. However, our data from primer extension analysis, S1 nuclease mapping, β-galactosidase assays, and in vitro transcription analysis all indicate that fis P is the sole E. coli fis promoter in vivo and in vitro. We further show how certain conditions used in the primer extension reactions can generate artifacts resulting from secondary annealing events that are the likely source of incorrect assignment of additional fis promoters.

scholarly journals The emerging role of microRNAs in bone remodeling and its therapeutic implications for osteoporosis

2018 ◽  
Vol 38 (3) ◽  
Author(s):  
Qianyun Feng ◽  
Sheng Zheng ◽  
Jia Zheng
Keyword(s):  
Bone Remodeling ◽  
Noncoding Rna ◽  
Target Genes ◽  
Epigenetic Modification ◽  
Therapeutic Implications ◽  
Small Noncoding Rna ◽  
Genetic And Environmental Factors ◽  
Underlying Mechanisms ◽  
Post Transcriptional Regulation

Osteoporosis, a common and multifactorial disease, is influenced by genetic factors and environments. However, the pathogenesis of osteoporosis has not been fully elucidated yet. Recently, emerging evidence suggests that epigenetic modifications may be the underlying mechanisms that link genetic and environmental factors with increased risks of osteoporosis and bone fracture. MicroRNA (miRNA), a major category of small noncoding RNA with 20–22 bases in length, is recognized as one important epigenetic modification. It can mediate post-transcriptional regulation of target genes with cell differentiation and apoptosis. In this review, we aimed to profile the role of miRNA in bone remodeling and its therapeutic implications for osteoporosis. A deeper insight into the role of miRNA in bone remodeling and osteoporosis can provide unique opportunities to develop a novel diagnostic and therapeutic approach of osteoporosis.

scholarly journals Human microRNAs in host–parasite interaction: a review

3 Biotech ◽  
2020 ◽  
Vol 10 (12) ◽  
Author(s):  
Sujay Paul ◽  
Luis M. Ruiz-Manriquez ◽  
Francisco I. Serrano-Cano ◽  
Carolina Estrada-Meza ◽  
Karla A. Solorio-Diaz ◽  
...  
Keyword(s):  
Noncoding Rna ◽  
Fine Tuning ◽  
Transcriptional Level ◽  
Response Modulation ◽  
Rna Molecules ◽  
Small Noncoding Rna ◽  
Diagnosis And Prognosis ◽  
Cell Proliferation And Differentiation ◽  
Host Parasite ◽  
The Impact

AbstractMicroRNAs (miRNAs) are a group of small noncoding RNA molecules with significant capacity to regulate the gene expression at the post-transcriptional level in a sequence-specific manner either through translation repression or mRNA degradation triggering a fine-tuning biological impact. They have been implicated in several processes, including cell growth and development, signal transduction, cell proliferation and differentiation, metabolism, apoptosis, inflammation, and immune response modulation. However, over the last few years, extensive studies have shown the relevance of miRNAs in human pathophysiology. Common human parasitic diseases, such as Malaria, Leishmaniasis, Amoebiasis, Chagas disease, Schistosomiasis, Toxoplasmosis, Cryptosporidiosis, Clonorchiasis, and Echinococcosis are the leading cause of death worldwide. Thus, identifying and characterizing parasite-specific miRNAs and their host targets, as well as host-related miRNAs, are important for a deeper understanding of the pathophysiology of parasite-specific diseases at the molecular level. In this review, we have demonstrated the impact of human microRNAs during host−parasite interaction as well as their potential to be used for diagnosis and prognosis purposes.

scholarly journals A Novel Point Mutation Promotes Growth Phase-Dependent Daptomycin Tolerance in Staphylococcus aureus

2015 ◽  
Vol 59 (9) ◽  
pp. 5366-5376 ◽  
Author(s):  
Lukas Mechler ◽  
Alexander Herbig ◽  
Kerstin Paprotka ◽  
Martin Fraunholz ◽  
Kay Nieselt ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Point Mutation ◽  
Growth Phase ◽  
Drug Tolerance ◽  
Stationary Growth Phase ◽  
Cellular Functions ◽  
Upstream Gene ◽  
Content Type ◽  
High Degree

ABSTRACTRecalcitrance of genetically susceptible bacteria to antibiotic killing is a hallmark of bacterial drug tolerance. This phenomenon is prevalent in biofilms, persisters, and also planktonic cells and is associated with chronic or relapsing infections with pathogens such asStaphylococcus aureus. Here we report thein vitroevolution of anS. aureusstrain that exhibits a high degree of nonsusceptibility to daptomycin as a result of cyclic challenges with bactericidal concentrations of the drug. This phenotype was attributed to stationary growth phase-dependent drug tolerance and was clearly distinguished from resistance. The underlying genetic basis was revealed to be an adaptive point mutation in the putative inorganic phosphate (Pi) transporter genepitA. Drug tolerance caused by this allele, termedpitA6, was abrogated when the upstream genepitRwas inactivated. Enhanced tolerance toward daptomycin, as well as the acyldepsipeptide antibiotic ADEP4 and various combinations of other drugs, was accompanied by elevated intracellular concentrations of Piand polyphosphate, which may reversibly interfere with critical cellular functions. The evolved strain displayed increased rates of survival within human endothelial cells, demonstrating the correlation of intracellular persistence and drug tolerance. These findings will be useful for further investigations ofS. aureusdrug tolerance, toward the development of additional antipersister compounds and strategies.

scholarly journals Heteromeric Interactions among Nucleoid-Associated Bacterial Proteins: Localization of StpA-Stabilizing Regions in H-NS of Escherichia coli

2001 ◽  
Vol 183 (7) ◽  
pp. 2343-2347 ◽  
Author(s):  
Jörgen Johansson ◽  
Sven Eriksson ◽  
Berit Sondén ◽  
Sun Nyunt Wai ◽  
Bernt Eric Uhlin
Keyword(s):  
Escherichia Coli ◽  
Stable Form ◽  
Lon Protease ◽  
Wild Type ◽  
Bacterial Proteins ◽  
Regulatory Systems ◽  
Associated Proteins ◽  
Gene Regulatory

ABSTRACT The nucleoid-associated proteins H-NS and StpA inEscherichia coli bind DNA as oligomers and are implicated in gene regulatory systems. There is evidence for both homomeric and heteromeric H-NS–StpA complexes. The two proteins show differential turnover, and StpA was previously found to be subject to protease-mediated degradation by the Lon protease. We investigated which regions of the H-NS protein are able to prevent degradation of StpA. A set of truncated H-NS derivatives was tested for their ability to mediate StpA stability and to form heteromers in vitro. The data indicate that H-NS interacts with StpA at two regions and that the presence of at least one of the H-NS regions is necessary for StpA stability. Our results also suggest that a proteolytically stable form of StpA, StpAF21C, forms dimers, whereas wild-type StpA in the absence of H-NS predominantly forms tetramers or oligomers, which are more susceptible to proteolysis.

scholarly journals The RNA Chaperone Hfq Is Required for Virulence of Bordetella pertussis

2013 ◽  
Vol 81 (11) ◽  
pp. 4081-4090 ◽  
Author(s):  
Ilona Bibova ◽  
Karolina Skopova ◽  
Jiri Masin ◽  
Ondrej Cerny ◽  
David Hot ◽  
...  
Keyword(s):  
Bordetella Pertussis ◽  
Posttranscriptional Regulation ◽  
Noncoding Rna ◽  
Whooping Cough ◽  
Lethal Dose ◽  
Rna Chaperone ◽  
Content Type ◽  
Small Noncoding Rna ◽  
Mrna Targets

ABSTRACTBordetella pertussisis a Gram-negative pathogen causing the human respiratory disease called pertussis or whooping cough. Here we examined the role of the RNA chaperone Hfq inB. pertussisvirulence. Hfq mediates interactions between small regulatory RNAs and their mRNA targets and thus plays an important role in posttranscriptional regulation of many cellular processes in bacteria, including production of virulence factors. We characterized anhfqdeletion mutant (Δhfq) ofB. pertussis18323 and show that the Δhfqstrain produces decreased amounts of the adenylate cyclase toxin that plays a central role inB. pertussisvirulence. Production of pertussis toxin and filamentous hemagglutinin was affected to a lesser extent.In vitro, the ability of the Δhfqstrain to survive within macrophages was significantly reduced compared to that of the wild-type (wt) strain. The virulence of the Δhfqstrain in the mouse respiratory model of infection was attenuated, with its capacity to colonize mouse lungs being strongly reduced and its 50% lethal dose value being increased by one order of magnitude over that of the wt strain. In mixed-infection experiments, the Δhfqstrain was then clearly outcompeted by the wt strain. This requirement for Hfq suggests involvement of small noncoding RNA regulation inB. pertussisvirulence.

scholarly journals DksA Is Required for Growth Phase-Dependent Regulation, Growth Rate-Dependent Control, and Stringent Control of fis Expression in Escherichia coli

2006 ◽  
Vol 188 (16) ◽  
pp. 5775-5782 ◽  
Author(s):  
Prabhat Mallik ◽  
Brian J. Paul ◽  
Steven T. Rutherford ◽  
Richard L. Gourse ◽  
Robert Osuna
Keyword(s):  
Escherichia Coli ◽  
Growth Rate ◽  
Amino Acid ◽  
Rna Polymerase ◽  
Growth Phase ◽  
Stationary Growth ◽  
Rate Dependent ◽  
Transcription In Vitro ◽  
State Growth

ABSTRACT DksA is a critical transcription factor in Escherichia coli that binds to RNA polymerase and potentiates control of rRNA promoters and certain amino acid promoters. Given the kinetic similarities between rRNA promoters and the fis promoter (Pfis), we investigated the possibility that DksA might also control transcription from Pfis. We show that the absence of dksA extends transcription from Pfis well into the late logarithmic and stationary growth phases, demonstrating the importance of DksA for growth phase-dependent regulation of fis. We also show that transcription from Pfis increases with steady-state growth rate and that dksA is absolutely required for this regulation. In addition, both DksA and ppGpp are required for inhibition of Pfis promoter activity following amino acid starvation, and these factors act directly and synergistically to negatively control Pfis transcription in vitro. DksA decreases the half-life of the intrinsically short-lived fis promoter-RNA polymerase complex and increases its sensitivity to the concentration of CTP, the predominant initiating nucleotide triphosphate for this promoter. This work extends our understanding of the multiple factors controlling fis expression and demonstrates the generality of the DksA requirement for regulation of kinetically similar promoters.

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