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Accueil > Séminaires

Département Biochimie, Biophysique et Biologie Structurale

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Agenda

  • Lundi 27 mai 11:00-12:00 - Jérôme Gouge - Structural Biology Department, Institute of Cancer Research, London, UK.

    Human RNA polymerase III recruitment at the type 3 promoters

    Résumé : The RNA Polymerase III controls transcription of the short and untranslated RNA, such as the entire pool of tRNA. Its recruitment relies on 3 subunits : i) TBP, ii) Bdp1 that opens the DNA bubble and iii) either Brf1 or Brf2. While Brf1 is found across all eukaryotes at type 1 and 2 promoters, Brf2 is present only in higher metazoans at the type 3 promoters. Brf2 has been linked to tumorigenesis but the underlying mechanisms remain elusive. Integration of structural, biochemical and in vitro data provided a model explaining Brf2 activation in cancer and how the promoter can be opened in the Pol III system in absence of ATP hydrolysis.

    Lieu : Auditorium I2BC - Bât. 21, Campus de Gif-sur-Yvette

    Notes de dernières minutes : Candidature à une création d’équipe ATIP


  • Jeudi 6 juin 11:00-12:00 - Sandra de Macedo Ribeiro - Instituto de Biologia Molecular e Celular – IBMC, Porto, Portugal

    Dissecting the ataxin-3 aggregation pathways

    Résumé : Machado-Joseph disease is a neurodegenerative disorder caused by expansion the polyQ tract of ataxin-3 (Atx3). This protein contains a globular Josephin domain (JD) and a C-terminal tail containing the polyQ segment. Aggregation of Atx3 is well characterized and is critically dependent on early self-assembly events modulated by the JD. Biophysical studies unveiled Atx3 multistep aggregation pathway, but structural and mechanistic details of the aggregation process are still lacking. To provide a time-resolved perspective on Atx3 aggregation pathway(s), Atx3 self-assembly was monitored by dynamic light scattering, Thioflavin-T fluorescence, size exclusion chromatography and Electron Microscopy. Those studies were combined with biophysical modeling and experimental determination of equilibrium dissociation constants to provide an unprecedented quantitative perspective of the Atx3 aggregation mechanisms. The talk will discuss how experimental and theoretical approaches permit the identification of deviations from the simple nucleation-polymerization mechanism and suggest the presence of Atx3 aggregation pathways parallel to amyloid fibrillation. This knowledge is critical to understand the mechanisms underlying the effect of different Atx3 binding molecules for on- and off- pathway aggregation steps.
    Contact : Julie Ménétrey

    Lieu : Bibliothèque - Bâtiment 34, campus de Gif-sur-Yvette


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