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Département Biologie des Génomes

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  • Vendredi 20 octobre 11:00-12:00 - Dr Bertrand Séraphin - IGBMC - CNRS UMR 7104/INSERM U964/Unistra

    Starting from the end : mechanisms, regulation, and pathological implications of mRNA decay

    Résumé : In eukaryotic cells, gene expression is a complex process that is initiated in the nucleus by the transcription of pre-mRNAs followed by their processing before the export of the mature RNAs to the cytoplasm. In this compartment, mRNAs are translated, sometime after storage and/or localization, and finally degraded. Regulation at all steps of this process may contribute to the quantitative, spatial and temporal control of polypeptide production.
    It has recently become clear that mRNA decay contributes similarly to transcription to regulated protein production. We are interested to decipher the mechanisms controlling gene expression at the level of RNA decay. Eukaryotic mRNAs are protected at their two extremities by specific structures : a cap at the 5’ end and a poly(A) tail at the 3’ end. We have identified proteins involved in eliminating these protective groups and are characterizing their functions in yeast and human cells using whenever possible essential insights provided by collaborative structural analyses. Mechanisms ensuring the regulation of these factors and the control of mRNA decay will be also presented. Alterations of some of these factors in human diseases demonstrate further the physiological importance of mRNA turnover pathways.
    Contact : Michel WERNER

    Lieu : Auditorium - Bâtiment 21, Campus de Gif

  • Vendredi 27 octobre 11:00-12:00 - Dr Nick Dixon

    The bacterial replisome : design principles for a dynamic molecular machin

    Résumé : The bacterial replisome is a complex and dynamic assembly of more than 20 protein subunits that include the multi-protein Pol III chromosomal replicase and the primosome (helicase/primase). The replisome works on double-stranded DNA to achieve simultaneous copying of both strands at a replication fork at rates that approach 1000 bp/s, with near-perfect fidelity. In the textbook view, leading and lagging strand DNA replication are perfectly coordinated processes that are orchestrated to occur deterministically in discrete steps in space and time. However, there is no evolutionary pressure to achieve such elegance, nor do fundamental chemical principles allow it. I will integrate some recent structural and single-molecule biophysical studies that are being used to develop a new picture of replisomal function that is messier than the textbook view.
    Bio : Nick Dixon is Professor of Biological Chemistry and Director, Centre for Medical and Molecular Bioscience at the University of Wollongong, where he has worked since 2006. He was an Australian Research Council Professorial Fellow in 2008–12. He was trained in Biochemistry at the University of Queensland, and had postdoctoral positions at the Australian National University (ANU, Canberra) and Stanford University (Australian NHMRC C.J. Martin and Fulbright Fellowships) before returning to the John Curtin School of Medical Research at ANU as a Queen Elizabeth II Fellow. He established his independent research group at the Research School of Chemistry, ANU in 1986. His major research focus over the past 36 years has been to use the bacterial DNA replication apparatus as a model system to uncover the basic operating principles of Nature’s dynamic multiprotein machines.
    Contact : Bénédicte MICHEL

    Lieu : Bibliothèque - Bâtiment 34, campus de Gif

  • Vendredi 3 novembre 11:00-12:00 - Tung Le - Department of Molecular Microbiology, John Innes Centre, Norwich, UK

    Divorcing chromosomes still need rings : the role of an ancestral SMC protein in bacterial chromosome organisation and segregation

    Résumé : The Structural Maintenance of Chromosomes (SMC) complex plays an important role in chromosome organization and segregation in most living organisms. In Caulobacter crescentus, SMC is required to align the left and the right arms of the chromosome that run in parallel down the long axis of the cell. However, the mechanism of SMC-mediated alignment of chromosomal arms remains elusive. Here, using a genome-wide chromosome conformation capture assay, chromatin immunoprecipitation with deep sequencing, and microscopy of single cells, we show that Caulobacter SMC is recruited to the centromeric parS site and that SMC-mediated arm alignment depends on the chromosome partitioning protein ParB. We provide evidence that SMC likely tethers the parS-proximal regions of the chromosomal arms together, promoting arm alignment. Strikingly, the co-orientation of SMC translocation and the transcription of highly-expressed genes is crucial for the alignment of parS-proximal regions of the chromosomal arms. Highly-transcribed genes near parS that are oriented against SMC translocation disrupt arm alignment suggesting that head-on transcription interferes with SMC translocation. Our results demonstrate a tight interdependence of bacterial chromosome organization and global patterns of transcription.
    Contact : Vicky Lioy <virginia.lioy>
    , BOCCARD Frederic <Frederic.BOCCARD>

    Lieu : Salle des séminaires- bâtiment 26 - Campus CNRS de Gif-sur-Yvette

  • Vendredi 10 novembre 11:00-12:00 - Romain Koszul - Pasteur Institute

    titre à venir

    Résumé : Abstract TBA
    Contact : YAMAICHI Yoshiharu <yoshiharu.yamaichi>
    BOCCARD Frederic <Frederic.BOCCARD>

    Lieu : Salle des séminaires- bâtiment 26 - Campus CNRS de Gif-sur-Yvette

  • Vendredi 17 novembre 11:00-12:00 - Jesper Svejstrup

    titre à venir

    Résumé : Abstract TBA
    invited by Michel Werner

    Lieu : Bibliothèque - bâtiment 34 - Campus CNRS de Gif-sur-Yvette

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