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  • 1
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    eIF5 has GDI activity necessary for translational control by eIF2 phosphorylation (2010)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2010-05-21
    Description: In protein synthesis initiation, the eukaryotic translation initiation factor (eIF) 2 (a G protein) functions in its GTP-bound state to deliver initiator methionyl-tRNA (tRNA(i)(Met)) to the small ribosomal subunit and is necessary for protein synthesis in all cells. Phosphorylation of eIF2 [eIF2(alphaP)] is critical for translational control in diverse settings including nutrient deprivation, viral infection and memory formation. eIF5 functions in start site selection as a GTPase accelerating protein (GAP) for the eIF2.GTP.tRNA(i)(Met) ternary complex within the ribosome-bound pre-initiation complex. Here we define new regulatory functions of eIF5 in the recycling of eIF2 from its inactive eIF2.GDP state between successive rounds of translation initiation. First we show that eIF5 stabilizes the binding of GDP to eIF2 and is therefore a bi-functional protein that acts as a GDP dissociation inhibitor (GDI). We find that this activity is independent of the GAP function and identify conserved residues within eIF5 that are necessary for this role. Second we show that eIF5 is a critical component of the eIF2(alphaP) regulatory complex that inhibits the activity of the guanine-nucleotide exchange factor (GEF) eIF2B. Together our studies define a new step in the translation initiation pathway, one that is critical for normal translational controls.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2875157/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2875157/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Jennings, Martin D -- Pavitt, Graham D -- BB/E002005/1/Biotechnology and Biological Sciences Research Council/United Kingdom -- BB/H010599/1/Biotechnology and Biological Sciences Research Council/United Kingdom -- BBE0020051/Biotechnology and Biological Sciences Research Council/United Kingdom -- England -- Nature. 2010 May 20;465(7296):378-81. doi: 10.1038/nature09003.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Faculty of Life Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20485439" target="_blank"〉PubMed〈/a〉
    Keywords: Basic-Leucine Zipper Transcription Factors/metabolism ; Eukaryotic Initiation Factor-2/antagonists & inhibitors/chemistry/*metabolism ; GTPase-Activating Proteins/metabolism ; Guanine Nucleotide Dissociation Inhibitors/chemistry/*metabolism ; Guanosine Diphosphate/metabolism ; Guanosine Triphosphate/metabolism ; *Peptide Chain Initiation, Translational ; Peptide Initiation Factors/chemistry/*metabolism ; Phosphorylation ; Protein Binding ; Protein Subunits/chemistry/metabolism ; RNA, Transfer, Met/metabolism ; Saccharomyces cerevisiae/metabolism ; Saccharomyces cerevisiae Proteins/metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 2
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    Puf3p induces translational repression of genes linked to oxidative stress (2014)
    Oxford University Press
    Details
    Publication Date: 2014-01-28
    Description: In response to stress, the translation of many mRNAs in yeast can change in a fashion discordant with the general repression of translation. Here, we use machine learning to mine the properties of these mRNAs to determine specific translation control signals. We find a strong association between transcripts acutely translationally repressed under oxidative stress and those associated with the RNA-binding protein Puf3p, a known regulator of cellular mRNAs encoding proteins targeted to mitochondria. Under oxidative stress, a PUF3 deleted strain exhibits more robust growth than wild-type cells and the shift in translation from polysomes to monosomes is attenuated, suggesting puf3 cells perceive less stress. In agreement, the ratio of reduced:oxidized glutathione, a major antioxidant and indicator of cellular redox state, is increased in unstressed puf3 cells but remains lower under stress. In untreated conditions, Puf3p migrates with polysomes rather than ribosome-free fractions, but this is lost under stress. Finally, reverse transcriptase-polymerase chain reaction (RT-PCR) of Puf3p targets following affinity purification shows Puf3p-mRNA associations are maintained or increased under oxidative stress. Collectively, these results point to Puf3p acting as a translational repressor in a manner exceeding the global translational response, possibly by temporarily limiting synthesis of new mitochondrial proteins as cells adapt to the stress.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
    Published by Oxford University Press
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  • 3
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    eIF2{beta} is critical for eIF5-mediated GDP-dissociation inhibitor activity and translational control (2016)
    Oxford University Press
    Details
    Publication Date: 2016-12-01
    Description: In protein synthesis translation factor eIF2 binds initiator tRNA to ribosomes and facilitates start codon selection. eIF2 GDP/GTP status is regulated by eIF5 (GAP and GDI functions) and eIF2B (GEF and GDF activities), while eIF2α phosphorylation in response to diverse signals is a major point of translational control. Here we characterize a growth suppressor mutation in eIF2β that prevents eIF5 GDI and alters cellular responses to reduced eIF2B activity, including control of GCN4 translation. By monitoring the binding of fluorescent nucleotides and initiator tRNA to purified eIF2 we show that the eIF2β mutation does not affect intrinsic eIF2 affinities for these ligands, neither does it interfere with eIF2 binding to 43S pre-initiation complex components. Instead we show that the eIF2β mutation prevents eIF5 GDI stabilizing nucleotide binding to eIF2, thereby altering the off-rate of GDP from eIF2•GDP/eIF5 complexes. This enables cells to grow with reduced eIF2B GEF activity but impairs activation of GCN4 targets in response to amino acid starvation. These findings provide support for the importance of eIF5 GDI activity in vivo and demonstrate that eIF2β acts in concert with eIF5 to prevent premature release of GDP from eIF2 and thereby ensure tight control of protein synthesis initiation.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
    Published by Oxford University Press
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  • 4
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    Puf3p induces translational repression of genes linked to oxidative stress (2013)
    Oxford University Press
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    Publication Date: 2013-10-25
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
    Published by Oxford University Press
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  • 5
    Electronic Resource
    Electronic Resource
    Protein H1: a role for chromatin structure in the regulation of bacterial gene expression and virulence? (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 4 (1990), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: There has been a recent revival of interest in one of the most abundant Escherichia coli proteins, H1 (also called H-NS). This protein was first identified many years ago as a major component of the bacterial nucleoid, and has been characterized biochemically by several groups. However, no clear function for the protein emerged from these studies. Our thinking has been transformed by recent findings which complement the biochemistry with genetic data. Several mutations, selected over many years by virtue of their diverse effects on gene expression, have turned out to be allelic and to fall within the structural gene for H1. Bringing together the genetics and the biochemistry has demonstrated that the whole is worth more than the sum of the parts! These findings have far-reaching implications for the mechanisms by which gene expression is regulated and also, perhaps, for the control of bacterial virulence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1990.tb00559.x
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