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  • Article  (18)
  • AGRIS (United Nations, Food and Agriculture Organization)  (18)
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  • 1
    Language: English
    In: Molecular Cell, 10 October 2013, Vol.52(1), pp.4-7
    Description: Three papers in this issue of report on the structure and functional activity of type III CRISPR-Cas effector complexes, revealing novel and conserved features of the ribonucleoprotein particles that underlie prokaryotic genome defense. The new structures suggest that type I and type III complexes follow the same architectural principles and are most likely descendants of a common ancestor, the differences in RNA and protein sequences and structure of individual components notwithstanding.
    Keywords: Biology
    ISSN: 1097-2765
    E-ISSN: 1097-4164
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  • 2
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 2012, Vol.109(12), pp.4621-4626
    Description: The conserved RNA-binding protein Hfq and its associated small regulatory RNAs (sRNAs) are increasingly recognized as the players of a large network of posttranscriptional control of gene expression in Gram-negative bacteria. The role of Hfq in this network is to facilitate base pairing between sRNAs and their trans-encoded target mRNAs. Although the number of known sRNA–mRNA interactions has grown steadily, cellular factors that influence Hfq, the mediator of these interactions, have remained unknown. We report that RelA, a protein long known as the central regulator of the bacterial-stringent response, acts on Hfq and thereby affects the physiological activity of RyhB sRNA as a regulator of iron homeostasis. RyhB requires RelA in vivo to arrest growth during iron depletion and to down-regulate a subset of its target mRNAs (fdoG, nuoA, and sodA), whereas the sodB and sdhC targets are barely affected by RelA. In vitro studies with recombinant proteins show that RelA enhances multimerization of Hfq monomers and stimulates Hfq binding of RyhB and other sRNAs. Hfq from polysomes extracted from wild-type cells binds RyhB in vitro, whereas Hfq from polysomes of a relA mutant strain shows no binding. We propose that, by increasing the level of the hexameric form of Hfq, RelA enables binding of RNAs whose affinity for Hfq is low. Our results suggest that, under specific conditions and/or environments, Hfq concentrations are limiting for RNA binding, which thereby provides an opportunity for cellular proteins such as RelA to impact sRNA-mediated responses by modulating the activity of Hfq. ; p. 4621-4626.
    Keywords: Polyribosomes ; In Vitro Studies ; Messenger Rna ; Gram-Negative Bacteria ; Gene Expression ; Recombinant Proteins
    ISSN: 0027-8424
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  • 3
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 2011, Vol.108(5), pp.2124-2129
    Description: There has been an increasing interest in cyanobacteria because these photosynthetic organisms convert solar energy into biomass and because of their potential for the production of biofuels. However, the exploitation of cyanobacteria for bioengineering requires knowledge of their transcriptional organization. Using differential RNA sequencing, we have established a genome-wide map of 3,527 transcriptional start sites (TSS) of the model organism Synechocystis sp. PCC6803. One-third of all TSS were located upstream of an annotated gene; another third were on the reverse complementary strand of 866 genes, suggesting massive antisense transcription. Orphan TSS located in intergenic regions led us to predict 314 noncoding RNAs (ncRNAs). Complementary microarray-based RNA profiling verified a high number of noncoding transcripts and identified strong ncRNA regulations. Thus, ~64% of all TSS give rise to antisense or ncRNAs in a genome that is to 87% protein coding. Our data enhance the information on promoters by a factor of 40, suggest the existence of additional small peptide-encoding mRNAs, and provide corrected 5' annotations for many genes of this cyanobacterium. The global TSS map will facilitate the use of Synechocystis sp. PCC6803 as a model organism for further research on photosynthesis and energy research. ; Includes references ; p. 2124-2129.
    Keywords: Transcription (Genetics) -- Physiological Aspects ; Cyanobacteria -- Genetic Aspects ; Genetic Regulation -- Research ; Rna Polymerases -- Properties;
    ISSN: 0027-8424
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  • 4
    Language: English
    In: Cell, 11 April 2013, Vol.153(2), pp.426-437
    Description: Glucose homeostasis is strictly controlled in all domains of life. Bacteria that are unable to balance intracellular sugar levels and deal with potentially toxic phosphosugars cease growth and risk being outcompeted. Here, we identify the conserved haloacid dehalogenase (HAD)-like enzyme YigL as the previously hypothesized phosphatase for detoxification of phosphosugars and reveal that its synthesis is activated by an Hfq-dependent small RNA in . We show that the glucose-6-P-responsive small RNA SgrS activates YigL synthesis in a translation-independent fashion by the selective stabilization of a decay intermediate of the dicistronic messenger RNA (mRNA). Intriguingly, the major endoribonuclease RNase E, previously known to function together with small RNAs to degrade mRNA targets, is also essential for this process of mRNA activation. The exploitation of and targeted interference with regular RNA turnover described here may constitute a general route for small RNAs to rapidly activate both coding and noncoding genes. ► The bacterial small RNA SgrS posttranscriptionally activates the synthesis of YigL ► YigL is the previously hypothesized phosphatase that prevents phosphosugar toxicity ► SgrS activates yigL by a translation-independent mRNA-stabilization mechanism ► SgrS stabilizes an intermediate in the yigL mRNA decay pathway YigL, a long-sought bacterial phosphatase, regulates glucose-6-phosphate levels. A small regulatory RNA upregulates YigL synthesis by base pairing with the coding sequence of the preceding gene to interfere with endonucleolytic yigL mRNA decay.
    Keywords: Biology
    ISSN: 0092-8674
    E-ISSN: 1097-4172
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  • 5
    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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  • 6
    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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  • 7
    In: Molecular Microbiology, October 2009, Vol.74(2), pp.261-269
    Description: A recent meeting on ‘Regulatory RNAs in prokaryotes’ reflected the growing interest in this research topic. Almost 200 scientists met to discuss the identification, structure, function and mechanistic details of regulatory RNAs in bacteria and archaea. The topics included small regulatory RNAs, riboswitches, RNA thermosensors and CRISPR (lustered egularly nterspaced hort alindromic epeats) elements.
    Keywords: Rna;
    ISSN: 0950-382X
    E-ISSN: 1365-2958
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  • 8
    Language: English
    In: Molecular Cell, 16 September 2011, Vol.43(6), pp.880-891
    Description: Research on the discovery and characterization of small, regulatory RNAs in bacteria has exploded in recent years. These sRNAs act by base pairing with target mRNAs with which they share limited or extended complementarity, or by modulating protein activity, in some cases by mimicking other nucleic acids. Mechanistic insights into how sRNAs bind mRNAs and proteins, how they compete with each other, and how they interface with ribonucleases are active areas of discovery. Current work also has begun to illuminate how sRNAs modulate expression of distinct regulons and key transcription factors, thus integrating sRNA activity into extensive regulatory networks. In addition, the application of RNA deep sequencing has led to reports of hundreds of additional sRNA candidates in a wide swath of bacterial species. Most importantly, recent studies have served to clarify the abundance of remaining questions about how, when, and why sRNA-mediated regulation is of such importance to bacterial lifestyles.
    Keywords: Biology
    ISSN: 1097-2765
    E-ISSN: 1097-4164
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  • 9
    Language: English
    In: Molecular cell, 2012, Vol.47(6), pp.943-953
    Description: Numerous small non-coding RNAs (sRNAs) in bacteria modulate rates of translation initiation and degradation of target mRNAs, which they recognize through base-pairing facilitated by the RNA chaperone Hfq. Recent evidence indicates that the ternary complex of Hfq, sRNA and mRNA guides endoribonuclease RNase E to initiate turnover of both the RNAs. We show that a sRNA not only guides RNase E to a defined site in a target RNA, but also allosterically activates the enzyme by presenting a monophosphate group at the 5′-end of the cognate-pairing “seed.” Moreover, in the absence of the target the 5′-monophosphate makes the sRNA seed region vulnerable to an attack by RNase E against which Hfq confers no protection. These results suggest that the chemical signature and pairing status of the sRNA seed region may help to both ‘proofread’ recognition and activate mRNA cleavage, as part of a dynamic process involving cooperation of RNA, Hfq and RNase E. ; p. 943-953.
    Keywords: Translation (Genetics) ; Messenger Rna ; Bacteria ; Non-Coding Rna ; Ribonucleases
    ISSN: 1097-2765
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  • 10
    In: Molecular Microbiology, December 2009, Vol.74(6), pp.1497-1512
    Description: Exposure to oxygen and light generates photooxidative stress by the bacteriochlorophyll mediated formation of singlet oxygen (O) in . Our study reports the genome‐wide search for small RNAs (sRNAs) involved in the regulatory response to O. By using 454 pyrosequencing and Northern blot analysis, we identified 20 sRNAs from aerobic cultures or following treatment with O or superoxide (O). One sRNA was specifically induced by O and its expression depends on the extracytoplasmic function sigma factor RpoE. Two sRNAs induced by O and O were cotranscribed with upstream genes preceded by promoters with target sequences for the alternative sigma factors RpoH and RpoH. The most abundant sRNA was processed in the presence of O but not by O. From this and a second sRNA a conserved 3′‐segment accumulated from a larger precursor. Absence of the RNA chaperone Hfq changed the half‐lives, abundance and processing of O‐affected sRNAs. Orthologues of three sRNA genes are present in different alpha‐proteobacteria, but the majority was unique to or species. Our discovery that abundant sRNAs are affected by O exposure extends the knowledge on the role of sRNAs and Hfq in the regulatory response to oxidative stress.
    Keywords: Active Oxygen -- Analysis ; Genomics -- Analysis ; Molecular Chaperones -- Analysis ; Rna -- Analysis ; Superoxides -- Analysis;
    ISSN: 0950-382X
    E-ISSN: 1365-2958
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