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17 novembre 2020: 2 événements

  • Département Biochimie, Biophysique et Biologie Structurale

    Mardi 17 novembre 2020 11:30-13:30 - Dorit Hanein - Institut Pasteur, Paris

    Coupling molecular activation and its functional output through 4d multiscale imaging - Correlative light and cryogenic cellular tomography studies

    Résumé :

    How do cells employ large, macromolecular machineries in cellular processes ?
    Despite of their key roles in every biological process and accumulated knowledge of composition and interactions, how nanomachine assemblies are organized in cells remains a mystery, and simplified schematic “cartoons” are currently our primary source of information. This is a knowledge gap given the importance in development, cancer biology, and tissue engineering. Specifically today, in which pathogens are taking hold on these machineries to promote their own survival, inflicting havoc on their unwilling host.
    I plan on presenting how we can move beyond “cartoon biology” and generate quantitative, (sub)nanometer-scale, three-dimensional structures of various molecular machineries in their native environment and in well-defined functional states. I will describe progress towards a technology platform that combines a unique set of state-of-the art light and cryogenic electron microscopy technologies, mechanical engineering, and protein expertise to provide a direct sub-nanometer scale definition on how these nano-machines structurally adapts to collectively response to changes in the environment, and thus provide clues on how to avert their malfunction in disease or infection. 
    Invited by Julie Ménétrey
    Due to Covid-19 the seminar will be online :

    Lieu : Webinar

    En savoir plus : Département Biochimie, Biophysique et Biologie Structurale
  • Département Biologie des Génomes

    Mardi 17 novembre 2020 15:58-16:58 - Pierre Mandin - Laboratoire de Chimie Bactérienne UMR 7283

    A sRNA “ménage à trois” : Three sRNAs control Fe-S biogenesis in response to oxygen and iron stresses

    Résumé : Fe-S clusters are essential and ubiquitous cofactors involved in a plethora of reactions. Despite their usefulness, Fe-S clusters are extremely sensitive to oxidative stress and iron starvation. Fe-S biogenesis regulation is therefore crucial for cell viability. In E. coli, two main machineries are involved in Fe-S cluster production : ISC, the housekeeping system, and SUF, which is expressed under stress. IscR, itself an Fe-S cluster containing protein, is a transcriptional regulator that induces the synthesis of either system in function of its concentration and of its Fe-S cluster bound state.
    We show here that three sRNAs, FnrS, OxyS and RyhB regulate Fe-S biogenesis by controlling IscR concentration and activity. FnrS is expressed during anaerobiosis and directly represses IscR translation by binding the iscR mRNA. OxyS is induced by oxidative stress and activates IscR translation by a yet undefined mechanism. Finally, RyhB, which is expressed during iron starvation, was shown to repress the isc machinery. We show here that in this way RyhB indirectly controls IscR Fe-S maturation state and activity. To our knowledge this is the first case of a triple regulation by sRNAs happening at both transcriptional, post transcriptional and post-translational levels through direct and indirect mechanisms. We are currently exploring how these sRNAs control dynamically Fe-S biogenesis and help the cell face stressful conditions. In any case, such an exquisite control clearly puts IscR and Fe-S biogenesis at the very heart of stress response control by sRNAs.
    Séminaire en visio réservé aux membres de l’I2BC (lien sur l’agenda intranet)

    En savoir plus : Département Biologie des Génomes