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  • 2016  (60)
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  • 2016  (60)
  • 1
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 11 October 2016, Vol.113(41), pp.11591-11596
    Description: The functional annotation of transcriptomes and identification of noncoding RNA (ncRNA) classes has been greatly facilitated by the advent of next-generation RNA sequencing which, by reading the nucleotide order of transcripts, theoretically allows the rapid profiling of all transcripts in a cell. However, primary sequence per se is a poor predictor of function, as ncRNAs dramatically vary in length and structure and often lack identifiable motifs. Therefore, to visualize an informative RNA landscape of organisms with potentially new RNA biology that are emerging from microbiome and environmental studies requires the use of more functionally relevant criteria. One such criterion is the association of RNAs with functionally important cognate RNA-binding proteins. Here we analyze the full ensemble of cellular RNAs using gradient profiling by sequencing (Grad-seq) in the bacterial pathogen Salmonella enterica, partitioning its coding and noncoding transcripts based on their network of RNA-protein interactions. In addition to capturing established RNA classes based on their biochemical profiles, the Grad-seq approach enabled the discovery of an overlooked large collective of structured small RNAs that form stable complexes with the conserved protein ProQ. We show that ProQ is an abundant RNA-binding protein with a wide range of ligands and a global influence on Salmonella gene expression. Given its generic ability to chart a functional RNA landscape irrespective of transcript length and sequence diversity, Grad-seq promises to define functional RNA classes and major RNA-binding proteins in both model species and genetically intractable organisms.
    Keywords: Hfq ; Proq ; RNA–Protein Interaction ; Noncoding RNA ; Small RNA ; Bacterial Proteins -- Metabolism ; High-Throughput Nucleotide Sequencing -- Methods ; RNA, Bacterial -- Metabolism ; RNA-Binding Proteins -- Metabolism ; Salmonella Enterica -- Metabolism
    ISSN: 00278424
    E-ISSN: 1091-6490
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  • 2
    Language: English
    In: Philosophical transactions of the Royal Society of London. Series B, Biological sciences, 05 November 2016, Vol.371(1707)
    Description: Infection is a complicated balance, with both pathogen and host struggling to tilt the result in their favour. Bacterial infection biology has relied on forward genetics for many of its advances, defining phenotype in terms of replication in model systems. However, many known virulence factors fail to produce robust phenotypes, particularly in the systems most amenable to genetic manipulation, such as cell-culture models. This has particularly been limiting for the study of the bacterial regulatory small RNAs (sRNAs) in infection. We argue that new sequencing-based technologies can work around this problem by providing a 'molecular phenotype', defined in terms of the specific transcriptional dysregulation in the infection system induced by gene deletion. We illustrate this using the example of our recent study of the PinT sRNA using dual RNA-seq, that is, simultaneous RNA sequencing of host and pathogen during infection. We additionally discuss how other high-throughput technologies, in particular genetic interaction mapping using transposon insertion sequencing, may be used to further dissect molecular phenotypes. We propose a strategy for how high-throughput technologies can be integrated in the study of non-coding regulators as well as bacterial virulence factors, enhancing our ability to rapidly generate hypotheses with regards to their function.This article is part of the themed issue 'The new bacteriology'.
    Keywords: Pint ; Tn-Seq ; Dual RNA-Seq ; Host–Pathogen Interaction ; Infection ; Small Non-Coding RNA ; Chromosome Mapping -- Methods ; High-Throughput Nucleotide Sequencing -- Methods ; RNA, Bacterial -- Genetics ; RNA, Small Untranslated -- Genetics ; Sequence Analysis, RNA -- Methods
    ISSN: 09628436
    E-ISSN: 1471-2970
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  • 3
    Language: English
    In: PloS one, 2016, Vol.11(7), pp.e0159948
    Description: Matter turnover in soil is tightly linked to soil structure which governs the heterogeneous distribution of habitats, reaction sites and pathways in soil. Thereby, the temporal dynamics of soil structure alteration is deemed to be important for essential ecosystem functions of soil but very little is known about it. A major reason for this knowledge gap is the lack of methods to study soil structure turnover directly at microscopic scales. Here we devise a conceptual approach and an image processing workflow to study soil structure turnover by labeling some initial state of soil structure with small garnet particles and tracking their fate with X-ray microtomography. The particles adhere to aggregate boundaries at the beginning of the experiment but gradually change their position relative to the nearest pore as structure formation progresses and pores are destructed or newly formed. A new metric based on the contact distances between particles and pores is proposed that allows for a direct quantification of soil structure turnover rates. The methodology is tested for a case study about soil compaction of a silty loam soil during stepwise increase of bulk density (ρ = {1.1, 1.3, 1.5} g/cm3). We demonstrate that the analysis of mean contact distances provides genuinely new insights about changing diffusion pathways that cannot be inferred neither from conventional pore space attributes (porosity, mean pore size, pore connectivity) nor from deformation analysis with digital image correlation. This structure labeling approach to quantify soil structure turnover provides a direct analogy to stable isotope labeling for the analysis of matter turnover and can be readily combined with each other.
    Keywords: X-Ray Microtomography ; Soil -- Chemistry
    E-ISSN: 1932-6203
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  • 4
    Language: English
    In: Nature, 28 January 2016, Vol.529(7587), pp.496-501
    Description: Bacteria express many small RNAs for which the regulatory roles in pathogenesis have remained poorly understood due to a paucity of robust phenotypes in standard virulence assays. Here we use a generic 'dual RNA-seq' approach to profile RNA expression simultaneously in pathogen and host during Salmonella enterica serovar Typhimurium infection and reveal the molecular impact of bacterial riboregulators. We identify a PhoP-activated small RNA, PinT, which upon bacterial internalization temporally controls the expression of both invasion-associated effectors and virulence genes required for intracellular survival. This riboregulatory activity causes pervasive changes in coding and noncoding transcripts of the host. Interspecies correlation analysis links PinT to host cell JAK-STAT signalling, and we identify infection-specific alterations in multiple long noncoding RNAs. Our study provides a paradigm for a sensitive RNA-based analysis of intracellular bacterial pathogens and their hosts without physical separation, as well as a new discovery route for hidden functions of pathogen genes.
    Keywords: Gene Expression Regulation -- Genetics ; Host-Pathogen Interactions -- Genetics ; RNA, Bacterial -- Genetics ; RNA, Untranslated -- Genetics ; Salmonella Typhimurium -- Genetics
    ISSN: 00280836
    E-ISSN: 1476-4687
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  • 5
    In: Nucleic Acids Research, 2016, Vol. 44(21), pp.10406-10422
    Description: Model enteric bacteria such as Escherichia coli and Salmonella enterica express hundreds of small non-coding RNAs (sRNAs), targets for most of which are yet unknown. Some sRNAs are remarkably well conserved, indicating that they serve cellular functions that go beyond the necessities of a single species. One of these ‘core sRNAs’ of largely unknown function is the abundant ∼100-nucleotide SdsR sRNA which is transcribed by the general stress σ-factor, σ S and accumulates in stationary phase. In Salmonella , SdsR was known to inhibit the synthesis of the species-specific porin, OmpD. However, sdsR genes are present in almost all enterobacterial genomes, suggesting that additional, conserved targets of this sRNA must exist. Here, we have combined SdsR pulse-expression with whole genome transcriptomics to discover 20 previously unknown candidate targets of SdsR which include mRNAs coding for physiologically important regulators such as the carbon utilization regulator, CRP, the nucleoid-associated chaperone, StpA and the antibiotic resistance transporter, TolC. Processing of SdsR by RNase E results in two cellular SdsR variants with distinct target spectra. While the overall physiological role of this orphan core sRNA remains to be fully understood, the new SdsR targets present valuable leads to determine sRNA functions in resting bacteria.
    Keywords: Chemistry ; Anatomy & Physiology;
    ISSN: 0305-1048
    E-ISSN: 1362-4962
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  • 6
    Language: English
    In: Journal of bacteriology, 15 September 2016, Vol.198(18), pp.2410-8
    Description: Bacteroides is a major component of the human gut microbiota which has a broad impact on the development and physiology of its host and a potential role in a wide range of disease syndromes. The predominance of this genus is due in large part to expansion of paralogous gene clusters, termed polysaccharide utilization loci (PULs), dedicated to the uptake and catabolism of host-derived and dietary polysaccharides. The nutritive value and availability of polysaccharides in the gut vary greatly; thus, their utilization is hierarchical and strictly controlled. A typical PUL includes regulatory genes that induce PUL expression in response to the presence of specific glycan substrates. However, the existence of additional regulatory mechanisms has been predicted to explain phenomena such as hierarchical control and catabolite repression. In this report, a previously unknown layer of regulatory control was discovered in Bacteroides fragilis Exploratory transcriptome sequencing (RNA-seq) analysis revealed the presence of cis-encoded antisense small RNAs (sRNAs) associated with 15 (30%) of the B. fragilis PULs. A model system using the Don (degradation of N-glycans) PUL showed that the donS sRNA negatively regulated Don expression at the transcriptional level, resulting in a decrease in N-glycan utilization. Additional studies performed with other Bacteroides species indicated that this regulatory mechanism is highly conserved and, interestingly, that the regulated PULs appear to be closely linked to the utilization of host-derived glycans rather than dietary plant polysaccharides. The findings described here demonstrate a global control mechanism underlying known PUL regulatory circuits and provide insight into regulation of Bacteroides physiology. The human gut is colonized by a dense microbiota which is essential to the health and normal development of the host. A key to gut homeostasis is the preservation of a stable, diverse microbiota. Bacteroides is a dominant genus in the gut, and the ability of Bacteroides species to efficiently compete for a wide range of glycan energy sources is a crucial advantage for colonization. Glycan utilization is mediated by a large number of polysaccharide utilization loci (PULs) which are regulated by substrate induction. In this report, a novel family of antisense sRNAs is described whose members repress gene expression in a distinct subset of PULs. This repression downregulates PUL expression in the presence of energy sources that are more readily utilized such as glucose, thereby allowing efficient glycan utilization.
    Keywords: Bacteroides -- Metabolism ; Gene Expression Regulation, Bacterial -- Physiology ; Polysaccharides -- Metabolism ; RNA, Bacterial -- Metabolism ; RNA, Small Interfering -- Metabolism
    ISSN: 00219193
    E-ISSN: 1098-5530
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  • 7
    Language: English
    In: Molecular Cell, 04 February 2016, Vol.61(3), pp.352-363
    Description: Small RNAs (sRNAs) from conserved noncoding genes are crucial regulators in bacterial signaling pathways but have remained elusive in the Cpx response to inner membrane stress. Here we report that an alternative biogenesis pathway releasing the conserved mRNA 3′ UTR of stress chaperone CpxP as an ∼60-nt sRNA provides the noncoding arm of the Cpx response. This so-called CpxQ sRNA, generated by general mRNA decay through RNase E, acts as an Hfq-dependent repressor of multiple mRNAs encoding extracytoplasmic proteins. Both CpxQ and the Cpx pathway are required for cell survival under conditions of dissipation of membrane potential. Our discovery of CpxQ illustrates how the conversion of a transcribed 3′ UTR into an sRNA doubles the output of a single mRNA to produce two factors with spatially segregated functions during inner membrane stress: a chaperone that targets problematic proteins in the periplasm and a regulatory RNA that dampens their synthesis in the cytosol. Chao and Vogel discover that a small RNA cleaved off the 3′ end of an mRNA provides the elusive regulatory noncoding arm of the bacterial Cpx response to inner membrane stress.
    Keywords: Cpx Pathway ; Cpxp ; Cpxq ; 3′ Utr ; Hfq ; Rnase E ; Noncoding RNA ; Nhab ; Envelope Stress ; Membrane Potential ; Biology
    ISSN: 1097-2765
    E-ISSN: 1097-4164
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  • 8
    Language: English
    In: EMBO journal: European Molecular Biology Organization, 2016, Issue 9, pp.991-1011
    Description: The molecular roles of many RNA‐binding proteins in bacterial post‐transcriptional gene regulation are not well understood. Approaches combining in vivo UV crosslinking with RNA deep sequencing (CLIP‐seq) have begun to revolutionize the transcriptome‐wide mapping of eukaryotic RNA‐binding protein target sites. We have applied CLIP‐seq to chart the target landscape of two major bacterial post‐transcriptional regulators, Hfq and CsrA, in the model pathogen Salmonella Typhimurium. By detecting binding sites at single‐nucleotide resolution, we identify RNA preferences and structural constraints of Hfq and CsrA during their interactions with hundreds of cellular transcripts. This reveals 3′‐located Rho‐independent terminators as a universal motif involved in Hfq–RNA interactions. Additionally, Hfq preferentially binds 5′ to sRNA‐target sites in mRNAs, and 3′ to seed sequences in sRNAs, reflecting a simple logic in how Hfq facilitates sRNA–mRNA interactions. Importantly, global knowledge of Hfq sites significantly improves sRNA‐target predictions. CsrA binds AUGGA sequences in apical loops and targets many Salmonella virulence mRNAs. Overall, our generic CLIP‐seq approach will bring new insights into post‐transcriptional gene regulation by RNA‐binding proteins in diverse bacterial species.
    Keywords: Clip ; Csra ; Hfq ; Non‐Coding Rna ; Peak Calling ; Post‐Transcriptional Control ; Small Rna ; Terminator ; Translation
    ISSN: 0261-4189
    Source: Fundación Dialnet
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  • 9
    In: EMBO Journal, 02 May 2016, Vol.35(9), pp.991-1011
    Description: The molecular roles of many ‐binding proteins in bacterial post‐transcriptional gene regulation are not well understood. Approaches combining crosslinking with deep sequencing (‐seq) have begun to revolutionize the transcriptome‐wide mapping of eukaryotic ‐binding protein target sites. We have applied ‐seq to chart the target landscape of two major bacterial post‐transcriptional regulators, Hfq and CsrA, in the model pathogen Typhimurium. By detecting binding sites at single‐nucleotide resolution, we identify preferences and structural constraints of Hfq and CsrA during their interactions with hundreds of cellular transcripts. This reveals 3′‐located Rho‐independent terminators as a universal motif involved in Hfq– interactions. Additionally, Hfq preferentially binds 5′ to ‐target sites in s, and 3′ to seed sequences in s, reflecting a simple logic in how Hfq facilitates – interactions. Importantly, global knowledge of Hfq sites significantly improves ‐target predictions. CsrA binds sequences in apical loops and targets many virulence s. Overall, our generic ‐seq approach will bring new insights into post‐transcriptional gene regulation by ‐binding proteins in diverse bacterial species. A new pipeline for ‐seq in maps global –protein interactions and offers a tool for improved understanding of post‐transcriptional control in bacteria. Transcriptome‐wide mapping of Hfq and CsrA target sites by CLIP‐seq. Rho‐independent terminators comprise a general Hfq‐binding motif. Hfq binds 5′ to sRNA‐binding sites in mRNA targets and 3′ to seed sequences in cognate the sRNAs. CsrA preferentially recognizes AUGGA sequences present in loops of hairpin structures. CsrA binds and regulates many mRNAs encoding virulence factors. A new pipeline for CLIP‐seq in maps global RNA–protein interactions and offers a tool for improved understanding of post‐transcriptional control in bacteria.
    Keywords: Clip ; Csra ; Hfq ; Non‐Coding Rna ; Peak Calling ; Post‐Transcriptional Control ; Small Rna ; Terminator ; Translation
    ISSN: 0261-4189
    E-ISSN: 1460-2075
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  • 10
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 31 May 2016, Vol.113(22), pp.E3101-10
    Description: Staphylococcus aureus is a major bacterial pathogen, which causes severe blood and tissue infections that frequently emerge by autoinfection with asymptomatically carried nose and skin populations. However, recent studies report that bloodstream isolates differ systematically from those found in the nose and skin, exhibiting reduced toxicity toward leukocytes. In two patients, an attenuated toxicity bloodstream infection evolved from an asymptomatically carried high-toxicity nasal strain by loss-of-function mutations in the gene encoding the transcription factor repressor of surface proteins (rsp). Here, we report that rsp knockout mutants lead to global transcriptional and proteomic reprofiling, and they exhibit the greatest signal in a genome-wide screen for genes influencing S. aureus survival in human cells. This effect is likely to be mediated in part via SSR42, a long-noncoding RNA. We show that rsp controls SSR42 expression, is induced by hydrogen peroxide, and is required for normal cytotoxicity and hemolytic activity. Rsp inactivation in laboratory- and bacteremia-derived mutants attenuates toxin production, but up-regulates other immune subversion proteins and reduces lethality during experimental infection. Crucially, inactivation of rsp preserves bacterial dissemination, because it affects neither formation of deep abscesses in mice nor survival in human blood. Thus, we have identified a spontaneously evolving, attenuated-cytotoxicity, nonhemolytic S. aureus phenotype, controlled by a pleiotropic transcriptional regulator/noncoding RNA virulence regulatory system, capable of causing S. aureus bloodstream infections. Such a phenotype could promote deep infection with limited early clinical manifestations, raising concerns that bacterial evolution within the human body may contribute to severe infection.
    Keywords: Ssr42 ; Staphylococcus Aureus ; Bloodstream Infection ; Rsp ; Toxicity Regulator ; Apoptosis ; Abscess -- Etiology ; Bacteremia -- Etiology ; Bacterial Proteins -- Genetics ; Mutation -- Genetics ; RNA, Untranslated -- Genetics ; Staphylococcal Infections -- Complications ; Virulence Factors -- Genetics
    ISSN: 00278424
    E-ISSN: 1091-6490
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