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  • Article  (20)
  • Gene Expression Regulation, Bacterial  (20)
  • Salmonella
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  • Article  (20)
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  • 1
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 27 March 2012, Vol.109(13), pp.E757-64
    Description: SgrS RNA is a model for the large class of Hfq-associated small RNAs that act to posttranscriptionally regulate bacterial mRNAs. The function of SgrS is well-characterized in nonpathogenic Escherichia coli, where it was originally shown to counteract glucose-phosphate stress by acting as a repressor of the ptsG mRNA, which encodes the major glucose transporter. We have discovered additional SgrS targets in Salmonella Typhimurium, a pathogen related to E. coli that recently acquired one-quarter of all genes by horizontal gene transfer. We show that the conserved short seed region of SgrS that recognizes ptsG was recruited to target the Salmonella-specific sopD mRNA of a secreted virulence protein. The SgrS-sopD interaction is exceptionally selective; we find that sopD2 mRNA, whose gene arose from sopD duplication during Salmonella evolution, is deaf to SgrS because of a nonproductive G-U pair in the potential SgrS-sopD2 RNA duplex vs. G-C in SgrS-sopD. In other words, SgrS discriminates the two virulence factor mRNAs at the level of a single hydrogen bond. Our study suggests that bacterial pathogens use their large suites of conserved Hfq-associated regulators to integrate horizontally acquired genes into existing posttranscriptional networks, just as conserved transcription factors are recruited to tame foreign genes at the DNA level. The results graphically illustrate the importance of the seed regions of bacterial small RNAs to select new targets with high fidelity and suggest that target predictions must consider all or none decisions by individual seed nucleotides.
    Keywords: Phylogeny ; Base Pairing -- Genetics ; Gene Transfer, Horizontal -- Genetics ; RNA, Bacterial -- Genetics ; Salmonella -- Genetics
    ISSN: 00278424
    E-ISSN: 1091-6490
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  • 2
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 23 November 2010, Vol.107(47), pp.20435-40
    Description: The abundant class of bacterial Hfq-associated small regulatory RNAs (sRNAs) parallels animal microRNAs in their ability to control multiple genes at the posttranscriptional level by short and imperfect base pairing. In contrast to the universal length and seed pairing mechanism of microRNAs, the sRNAs are heterogeneous in size and structure, and how they regulate multiple targets is not well understood. This paper provides evidence that a 5' located sRNA domain is a critical element for the control of a large posttranscriptional regulon. We show that the conserved 5' end of RybB sRNA recognizes multiple mRNAs of Salmonella outer membrane proteins by ≥7-bp Watson-Crick pairing. When fused to an unrelated sRNA, the 5' domain is sufficient to guide target mRNA degradation and maintain σ(E)-dependent envelope homeostasis. RybB sites in mRNAs are often conserved and flanked by 3' adenosine. They are found in a wide sequence window ranging from the upstream untranslated region to the deep coding sequence, indicating that some targets might be repressed at the level of translation, whereas others are repressed primarily by mRNA destabilization. Autonomous 5' domains seem more common in sRNAs than appreciated and might improve the design of synthetic RNA regulators.
    Keywords: Bacterial Outer Membrane Proteins -- Metabolism ; Gene Expression Regulation, Bacterial -- Genetics ; RNA, Messenger -- Metabolism ; Regulatory Sequences, Ribonucleic Acid -- Genetics ; Regulon -- Genetics ; Salmonella -- Genetics
    ISSN: 00278424
    E-ISSN: 1091-6490
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  • 3
    In: PLoS ONE, 2015, Vol.10(11)
    Description: Bacillus amyloliquefaciens subsp. plantarum FZB42 is a representative of Gram-positive plant-growth-promoting rhizobacteria (PGPR) that inhabit plant root environments. In order to better understand the molecular mechanisms of bacteria-plant symbiosis, we have systematically analyzed the primary transcriptome of strain FZB42 grown under rhizosphere-mimicking conditions using differential RNA sequencing (dRNA-seq). Our analysis revealed 4,877 transcription start sites for protein-coding genes, identified genes differentially expressed under different growth conditions, and corrected many previously mis-annotated genes. We also identified a large number of riboswitches and cis- encoded antisense RNAs, as well as trans- encoded small noncoding RNAs that may play important roles in the gene regulation of Bacillus . Overall, our analyses provided a landscape of Bacillus primary transcriptome and improved the knowledge of rhizobacteria-host interactions.
    Keywords: Research Article
    E-ISSN: 1932-6203
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  • 4
    In: Molecular Microbiology, September 2009, Vol.73(5), pp.737-741
    Description: Small regulatory RNAs (sRNAs) are well known to command bacterial protein synthesis by modulating the translation and decay of target mRNAs. Most sRNAs are specifically regulated by a cognate transcription factor under certain growth or stress conditions. Investigations of the conserved Hfq‐dependent MicM sRNA in (article by Poul Valentin‐Hansen and colleagues in this issue of ) and in have unravelled a novel type of gene regulation in which the chitobiose operon mRNA acts as an RNA trap to degrade the constitutively expressed MicM sRNA, thereby alleviating MicM‐mediated repression of the synthesis of the YbfM porin that is required for chitosugar uptake. The results suggest that ‘target’ mRNAs might be both prey and also predators of sRNAs.
    Keywords: Protein Synthesis ; Messenger Rna;
    ISSN: 0950-382X
    E-ISSN: 1365-2958
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  • 5
    In: Molecular Microbiology, January 2009, Vol.71(1), pp.1-11
    Description: species are enterobacterial pathogens that have been exceptionally well investigated with respect to virulence mechanisms, microbial pathogenesis, genome evolution and many fundamental pathways of gene expression and metabolism. While these studies have traditionally focused on protein functions, has also become a model organism for RNA‐mediated regulation. The present review is dedicated to the non‐coding RNA world of : it covers small RNAs (sRNAs) that act as post‐transcriptional regulators of gene expression, novel Salmonella ‐regulatory RNA elements that sense metabolite and metal ion concentrations (or temperature), and globally acting RNA‐binding proteins such as CsrA or Hfq (inactivation of which cause drastic phenotypes and virulence defects). Owing to mosaic genome structure, some of the sRNAs are widely conserved in bacteria whereas others are very specific to species. Intriguingly, sRNAs of either type (CsrB/C, InvR, SgrS) facilitate cross‐talk between the core genome and its laterally acquired virulence regions. Work in also identified physiological functions (and mechanisms thereof) of RNA that had remained unknown in , and pioneered the use of high‐throughput sequencing technology to identify the sRNA and mRNA targets of bacterial RNA‐binding proteins.
    Keywords: Metabolites ; Proteins ; Messenger Rna ; Salmonella ; Gene Expression;
    ISSN: 0950-382X
    E-ISSN: 1365-2958
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  • 6
    In: Molecular Microbiology, September 2011, Vol.81(5), pp.1144-1165
    Description: GcvB is one of the most highly conserved Hfq‐associated small RNAs in Gram‐negative bacteria and was previously reported to repress several ABC transporters for amino acids. To determine the full extent of GcvB‐mediated regulation in , we combined a genome‐wide experimental approach with biocomputational target prediction. Comparative pulse expression of wild‐type versus mutant sRNA variants revealed that GcvB governs a large post‐transcriptional regulon, impacting ∼1% of all genes via its conserved G/U‐rich domain R1. Complementary predictions of C/A‐rich binding sites in mRNAs and reporter fusion experiments increased the number of validated GcvB targets to more than 20, and doubled the number of regulated amino acid transporters. Unlike the previously described targeting via the single R1 domain, GcvB represses the glycine transporter CycA by exceptionally redundant base‐pairing. This novel ability of GcvB is focused upon the one target that could feedback‐regulate the glycine‐responsive synthesis of GcvB. Several newly discovered mRNA targets involved in amino acid metabolism, including the global regulator Lrp, question the previous assumption that GcvB simply acts to limit unnecessary amino acid uptake. Rather, GcvB rewires primary transcriptional control circuits and seems to act as a distinct regulatory node in amino acid metabolism.
    Keywords: Glycine -- Physiological Aspects ; Genetic Research -- Physiological Aspects ; Genomics -- Physiological Aspects ; Messenger Rna -- Physiological Aspects;
    ISSN: 0950-382X
    E-ISSN: 1365-2958
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  • 7
    In: Molecular Microbiology, May 2012, Vol.84(3), pp.428-445
    Description: MicF is a textbook example of a small regulatory RNA (sRNA) that acts on a ‐encoded target mRNA through imperfect base pairing. Discovery of MicF as a post‐transcriptional repressor of the major porin OmpF established the paradigm for a meanwhile common mechanism of translational inhibition, through antisense sequestration of a ribosome binding site. However, whether MicF regulates additional genes has remained unknown for almost three decades. Here, we have harnessed the new superfolder variant of GFP for reporter–gene fusions to validate newly predicted targets of MicF in . We show that the conserved 5′ end of MicF acts by seed pairing to repress the mRNAs of global transcriptional regulator Lrp, and periplasmic protein YahO, while a second targeting region is also required to regulate the mRNA of the lipid A‐modifying enzyme LpxR. Interestingly, MicF targets at both the ribosome binding site and deep within the coding sequence. MicF binding in the coding sequence of decreases mRNA stability through exacerbating the use of a native RNase E site proximal to the short MicF‐ duplex. Altogether, this study assigns the classic MicF sRNA to the growing class of Hfq‐associated regulators that use diverse mechanisms to impact multiple loci.
    Keywords: Gene Expression Regulation, Bacterial ; Bacterial Proteins -- Genetics ; Green Fluorescent Proteins -- Metabolism ; Porins -- Genetics ; RNA, Bacterial -- Metabolism ; RNA, Small Untranslated -- Metabolism ; Salmonella Typhimurium -- Metabolism;
    ISSN: 0950-382X
    E-ISSN: 1365-2958
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  • 8
    Language: English
    In: Nucleic acids research, April 2012, Vol.40(8), pp.3623-40
    Description: A remarkable feature of many small non-coding RNAs (sRNAs) of Escherichia coli and Salmonella is their accumulation in the stationary phase of bacterial growth. Several stress response regulators and sigma factors have been reported to direct the transcription of stationary phase-specific sRNAs, but a widely conserved sRNA gene that is controlled by the major stationary phase and stress sigma factor, σ(S) (RpoS), has remained elusive. We have studied in Salmonella the conserved SdsR sRNA, previously known as RyeB, one of the most abundant stationary phase-specific sRNAs in E. coli. Alignments of the sdsR promoter region and genetic analysis strongly suggest that this sRNA gene is selectively transcribed by σ(S). We show that SdsR down-regulates the synthesis of the major Salmonella porin OmpD by Hfq-dependent base pairing; SdsR thus represents the fourth sRNA to regulate this major outer membrane porin. Similar to the InvR, MicC and RybB sRNAs, SdsR recognizes the ompD mRNA in the coding sequence, suggesting that this mRNA may be primarily targeted downstream of the start codon. The SdsR-binding site in ompD was localized by 3'-RACE, an experimental approach that promises to be of use in predicting other sRNA-target interactions in bacteria.
    Keywords: Gene Expression Regulation, Bacterial ; Bacterial Proteins -- Metabolism ; Porins -- Biosynthesis ; RNA, Small Untranslated -- Metabolism ; Salmonella -- Genetics ; Sigma Factor -- Metabolism
    ISSN: 03051048
    E-ISSN: 1362-4962
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  • 9
    Language: English
    In: Nucleic acids research, 01 December 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 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: Gene Expression Regulation, Bacterial ; RNA Interference ; RNA, Bacterial -- Genetics ; RNA, Small Untranslated -- Genetics ; Salmonella -- Genetics
    E-ISSN: 1362-4962
    Source: MEDLINE/PubMed (U.S. National Library of Medicine)
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  • 10
    In: PLoS Genetics, 2016, Vol.12(4)
    Description: While an increasing number of conserved small regulatory RNAs (sRNAs) are known to function in general bacterial physiology, the roles and modes of action of sRNAs from horizontally acquired genomic regions remain little understood. The IsrK sRNA of Gifsy-1 prophage of Salmonella belongs to the latter class. This regulatory RNA exists in two isoforms. The first forms, when a portion of transcripts originating from isrK promoter reads-through the IsrK transcription-terminator producing a translationally inactive mRNA target. Acting in trans , the second isoform, short IsrK RNA, binds the inactive transcript rendering it translationally active. By switching on translation of the first isoform, short IsrK indirectly activates the production of AntQ, an antiterminator protein located upstream of isrK . Expression of antQ globally interferes with transcription termination resulting in bacterial growth arrest and ultimately cell death. Escherichia coli and Salmonella cells expressing AntQ display condensed chromatin morphology and localization of UvrD to the nucleoid. The toxic phenotype of AntQ can be rescued by co-expression of the transcription termination factor, Rho, or RNase H, which protects genomic DNA from breaks by resolving R-loops. We propose that AntQ causes conflicts between transcription and replication machineries and thus promotes DNA damage. The isrK locus represents a unique example of an island-encoded sRNA that exerts a highly complex regulatory mechanism to tune the expression of a toxic protein. Author Summary As the function of conserved core-genome-encoded small RNAs (sRNA) reflects the basic lifestyle of bacteria, the function of non-conserved island-encoded sRNAs remains enigmatic. The island-encoded sRNA IsrK belongs to Gifsy-1 prophage of Salmonella . Here, we report a complex mechanism in which the IsrK RNA functions as both sRNA and mRNA to control the production of the toxic AntQ protein. The isrK promoter directs the synthesis of two distinct RNA species: a full-length translationally inactive target mRNA and the correctly terminated, shorter IsrK sRNA. IsrK sRNA binds the full-length inactive mRNA producing an antiterminator protein, AntQ, which interferes with transcription termination. Expression of antQ results in bacterial growth arrest and ultimately cell death. Fluorescence microscopy of E . coli and Salmonella expressing antQ revealed condensed chromatin morphology as observed upon exposure to DNA-damaging agents. We propose that expression of the phage antiterminator protein results in conflicts between transcription and replication machineries and thus facilitates DNA damage. In summary, the RNA regulator IsrK presents a new regulatory principle in which a horizontally acquired sRNA controls genome integrity.
    Keywords: Research Article ; Biology And Life Sciences ; Biology And Life Sciences ; Medicine And Health Sciences ; Biology And Life Sciences ; Medicine And Health Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Research And Analysis Methods ; Biology And Life Sciences ; Biology And Life Sciences ; Research And Analysis Methods ; Research And Analysis Methods ; Biology And Life Sciences
    ISSN: 1553-7390
    E-ISSN: 1553-7404
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