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  • 1
    Publication Date: 2015-09-08
    Description: During eukaryotic translation initiation, 43S complexes, comprising a 40S ribosomal subunit, initiator transfer RNA and initiation factors (eIF) 2, 3, 1 and 1A, attach to the 5'-terminal region of messenger RNA and scan along it to the initiation codon. Scanning on structured mRNAs also requires the DExH-box protein DHX29. Mammalian eIF3 contains 13 subunits and participates in nearly all steps of translation initiation. Eight subunits having PCI (proteasome, COP9 signalosome, eIF3) or MPN (Mpr1, Pad1, amino-terminal) domains constitute the structural core of eIF3, to which five peripheral subunits are flexibly linked. Here we present a cryo-electron microscopy structure of eIF3 in the context of the DHX29-bound 43S complex, showing the PCI/MPN core at approximately 6 A resolution. It reveals the organization of the individual subunits and their interactions with components of the 43S complex. We were able to build near-complete polyalanine-level models of the eIF3 PCI/MPN core and of two peripheral subunits. The implications for understanding mRNA ribosomal attachment and scanning are discussed.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4719162/" 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/PMC4719162/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉des Georges, Amedee -- Dhote, Vidya -- Kuhn, Lauriane -- Hellen, Christopher U T -- Pestova, Tatyana V -- Frank, Joachim -- Hashem, Yaser -- R01 GM029169/GM/NIGMS NIH HHS/ -- R01 GM059660/GM/NIGMS NIH HHS/ -- R01 GM29169/GM/NIGMS NIH HHS/ -- R01 GM59660/GM/NIGMS NIH HHS/ -- Howard Hughes Medical Institute/ -- England -- Nature. 2015 Sep 24;525(7570):491-5. doi: 10.1038/nature14891. Epub 2015 Sep 7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉HHMI, Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA. ; Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, New York 11203, USA. ; CNRS, Proteomic Platform Strasbourg - Esplanade, Strasbourg 67084, France. ; Department of Biological Sciences, Columbia University, New York, New York 10032, USA. ; CNRS, Architecture et Reactivite de l'ARN, Universite de Strasbourg, Strasbourg 67084, France.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26344199" target="_blank"〉PubMed〈/a〉
    Keywords: Binding Sites ; Codon, Initiator/genetics ; Cryoelectron Microscopy ; Eukaryotic Initiation Factor-2/chemistry/metabolism ; Eukaryotic Initiation Factor-3/*chemistry/*metabolism ; Humans ; Models, Molecular ; Multiprotein Complexes/*chemistry/*metabolism ; *Peptide Chain Initiation, Translational ; Peptide Initiation Factors/metabolism ; Protein Structure, Secondary ; Protein Subunits/chemistry/metabolism ; RNA Helicases/chemistry/metabolism ; RNA, Messenger/genetics/metabolism ; RNA, Transfer, Met/metabolism ; Ribosome Subunits, Small, Eukaryotic/chemistry/metabolism ; Ribosomes/*chemistry/*metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2013-11-05
    Description: Hepatitis C virus (HCV) and classical swine fever virus (CSFV) messenger RNAs contain related (HCV-like) internal ribosome entry sites (IRESs) that promote 5'-end independent initiation of translation, requiring only a subset of the eukaryotic initiation factors (eIFs) needed for canonical initiation on cellular mRNAs. Initiation on HCV-like IRESs relies on their specific interaction with the 40S subunit, which places the initiation codon into the P site, where it directly base-pairs with eIF2-bound initiator methionyl transfer RNA to form a 48S initiation complex. However, all HCV-like IRESs also specifically interact with eIF3 (refs 2, 5-7, 9-12), but the role of this interaction in IRES-mediated initiation has remained unknown. During canonical initiation, eIF3 binds to the 40S subunit as a component of the 43S pre-initiation complex, and comparison of the ribosomal positions of eIF3 and the HCV IRES revealed that they overlap, so that their rearrangement would be required for formation of ribosomal complexes containing both components. Here we present a cryo-electron microscopy reconstruction of a 40S ribosomal complex containing eIF3 and the CSFV IRES. Remarkably, although the position and interactions of the CSFV IRES with the 40S subunit in this complex are similar to those of the HCV IRES in the 40S-IRES binary complex, eIF3 is completely displaced from its ribosomal position in the 43S complex, and instead interacts through its ribosome-binding surface exclusively with the apical region of domain III of the IRES. Our results suggest a role for the specific interaction of HCV-like IRESs with eIF3 in preventing ribosomal association of eIF3, which could serve two purposes: relieving the competition between the IRES and eIF3 for a common binding site on the 40S subunit, and reducing formation of 43S complexes, thereby favouring translation of viral mRNAs.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4106463/" 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/PMC4106463/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hashem, Yaser -- des Georges, Amedee -- Dhote, Vidya -- Langlois, Robert -- Liao, Hstau Y -- Grassucci, Robert A -- Pestova, Tatyana V -- Hellen, Christopher U T -- Frank, Joachim -- R01 AI51340/AI/NIAID NIH HHS/ -- R01 GM029169/GM/NIGMS NIH HHS/ -- R01 GM59660/GM/NIGMS NIH HHS/ -- R01GM29169/GM/NIGMS NIH HHS/ -- Howard Hughes Medical Institute/ -- England -- Nature. 2013 Nov 28;503(7477):539-43. doi: 10.1038/nature12658. Epub 2013 Nov 3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉1] Howard Hughes Medical Institute (HHMI), Department of Biochemistry and Molecular Biophysics, Columbia University, New York City, New York 10032, USA [2] Department of Biochemistry and Molecular Biophysics, Columbia University, New York City, New York 10032, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24185006" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Binding, Competitive ; Classical swine fever virus/*genetics ; Cryoelectron Microscopy ; Eukaryotic Initiation Factor-3/chemistry/*metabolism/ultrastructure ; Humans ; Models, Molecular ; Protein Biosynthesis ; RNA, Viral/*genetics/*metabolism ; Rabbits ; Regulatory Sequences, Ribonucleic Acid/*genetics ; Ribosome Subunits, Small, Eukaryotic/chemistry/*metabolism/ultrastructure ; Ribosomes/chemistry/*metabolism/ultrastructure
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 2013-02-12
    Description: Ribosomes, the protein factories of living cells, translate genetic information carried by messenger RNAs into proteins, and are thus involved in virtually all aspects of cellular development and maintenance. The few available structures of the eukaryotic ribosome reveal that it is more complex than its prokaryotic counterpart, owing mainly to the presence of eukaryote-specific ribosomal proteins and additional ribosomal RNA insertions, called expansion segments. The structures also differ among species, partly in the size and arrangement of these expansion segments. Such differences are extreme in kinetoplastids, unicellular eukaryotic parasites often infectious to humans. Here we present a high-resolution cryo-electron microscopy structure of the ribosome of Trypanosoma brucei, the parasite that is transmitted by the tsetse fly and that causes African sleeping sickness. The atomic model reveals the unique features of this ribosome, characterized mainly by the presence of unusually large expansion segments and ribosomal-protein extensions leading to the formation of four additional inter-subunit bridges. We also find additional rRNA insertions, including one large rRNA domain that is not found in other eukaryotes. Furthermore, the structure reveals the five cleavage sites of the kinetoplastid large ribosomal subunit (LSU) rRNA chain, which is known to be cleaved uniquely into six pieces, and suggests that the cleavage is important for the maintenance of the T. brucei ribosome in the observed structure. We discuss several possible implications of the large rRNA expansion segments for the translation-regulation process. The structure could serve as a basis for future experiments aimed at understanding the functional importance of these kinetoplastid-specific ribosomal features in protein-translation regulation, an essential step towards finding effective and safe kinetoplastid-specific drugs.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3659406/" 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/PMC3659406/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hashem, Yaser -- des Georges, Amedee -- Fu, Jie -- Buss, Sarah N -- Jossinet, Fabrice -- Jobe, Amy -- Zhang, Qin -- Liao, Hstau Y -- Grassucci, Robert A -- Bajaj, Chandrajit -- Westhof, Eric -- Madison-Antenucci, Susan -- Frank, Joachim -- R01 GM029169/GM/NIGMS NIH HHS/ -- R01 GM29169/GM/NIGMS NIH HHS/ -- R01-EB004873/EB/NIBIB NIH HHS/ -- R01-GM074258/GM/NIGMS NIH HHS/ -- T32 GM008798/GM/NIGMS NIH HHS/ -- Howard Hughes Medical Institute/ -- England -- Nature. 2013 Feb 21;494(7437):385-9. doi: 10.1038/nature11872. Epub 2013 Feb 10.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Howard Hughes Medical Institute, Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23395961" target="_blank"〉PubMed〈/a〉
    Keywords: *Cryoelectron Microscopy ; Models, Biological ; Models, Molecular ; Molecular Conformation ; Protein Biosynthesis ; RNA, Protozoan/genetics/metabolism ; RNA, Ribosomal/genetics/metabolism ; Ribosomes/chemistry/genetics/*ultrastructure ; Trypanosoma brucei brucei/chemistry/*cytology/genetics/*ultrastructure ; Yeasts/chemistry
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 4
    Publication Date: 2015-12-02
    Description: Plasmodium falciparum , the mosquito-transmitted Apicomplexan parasite, causes the most severe form of human malaria. In the asexual blood-stage, the parasite resides within erythrocytes where it proliferates, multiplies and finally spreads to new erythrocytes. Development of drugs targeting the ribosome, the site of protein synthesis, requires specific knowledge of its structure and work cycle, and, critically, the ways they differ from those in the human host. Here, we present five cryo-electron microscopy (cryo-EM) reconstructions of ribosomes purified from P. falciparum blood-stage schizonts at sub-nanometer resolution. Atomic models were built from these density maps by flexible fitting. Significantly, our study has taken advantage of new capabilities of cryo-EM, in visualizing several structures co-existing in the sample at once, at a resolution sufficient for building atomic models. We have discovered structural and dynamic features that differentiate the ribosomes of P. falciparum from those of mammalian system. Prompted by the absence of RACK1 on the ribosome in our and an earlier study we confirmed that RACK1 does not specifically co-purify with the 80S fraction in schizonts. More extensive studies, using cryo-EM methodology, of translation in the parasite will provide structural knowledge that may lead to development of novel anti-malarials.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
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  • 5
    Publication Date: 2014-03-13
    Description: Eukaryotic translation termination results from the complex functional interplay between two release factors, eRF1 and eRF3, in which GTP hydrolysis by eRF3 couples codon recognition with peptidyl-tRNA hydrolysis by eRF1. Here, we present a cryo-electron microscopy structure of pre-termination complexes associated with eRF1•eRF3•GDPNP at 9.7 -Å resolution, which corresponds to the initial pre-GTP hydrolysis stage of factor attachment and stop codon recognition. It reveals the ribosomal positions of eRFs and provides insights into the mechanisms of stop codon recognition and triggering of eRF3’s GTPase activity.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
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  • 6
    Publication Date: 2016-12-04
    Description: Comparative structural studies of ribosomes from various organisms keep offering exciting insights on how species-specific or environment-related structural features of ribosomes may impact translation specificity and its regulation. Although the importance of such features may be less obvious within more closely related organisms, their existence could account for vital yet species-specific mechanisms of translation regulation that would involve stalling, cell survival and antibiotic resistance. Here, we present the first full 70S ribosome structure from Staphylococcus aureus , a Gram-positive pathogenic bacterium, solved by cryo-electron microscopy. Comparative analysis with other known bacterial ribosomes pinpoints several unique features specific to S. aureus around a conserved core, at both the protein and the RNA levels. Our work provides the structural basis for the many studies aiming at understanding translation regulation in S. aureus and for designing drugs against this often multi-resistant pathogen.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
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  • 7
    Publication Date: 2007-02-25
    Print ISSN: 1367-4803
    Electronic ISSN: 1460-2059
    Topics: Biology , Computer Science , Medicine
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  • 8
    Publication Date: 2017-10-27
    Electronic ISSN: 2045-2322
    Topics: Natural Sciences in General
    Published by Springer Nature
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  • 9
    Publication Date: 2021-03-09
    Description: From 1985 to 2016, the prevalence of underweight decreased, and that of obesity and severe obesity increased, in most regions, with significant variation in the magnitude of these changes across regions. We investigated how much change in mean body mass index (BMI) explains changes in the prevalence of underweight, obesity, and severe obesity in different regions using data from 2896 population-based studies with 187 million participants. Changes in the prevalence of underweight and total obesity, and to a lesser extent severe obesity, are largely driven by shifts in the distribution of BMI, with smaller contributions from changes in the shape of the distribution. In East and Southeast Asia and sub-Saharan Africa, the underweight tail of the BMI distribution was left behind as the distribution shifted. There is a need for policies that address all forms of malnutrition by making healthy foods accessible and affordable, while restricting unhealthy foods through fiscal and regulatory restrictions.
    Electronic ISSN: 2050-084X
    Topics: Biology , Medicine , Natural Sciences in General
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