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Séminaire

  • Génomes

    • Vendredi 16 mars 11:00-12:00 - Damien Coudreuse - Institut de Génetique & Développement de Rennes

      Shaping cell proliferation : cell cycle progression and CDK activity dynamics

      Résumé : Cell cycle progression is central to cell proliferation in normal and pathological contexts. Despite the complexity of the eukaryotic cell cyclecontrol, we previously showed that the core engine of cell proliferation relies on the simple oscillation of a single qualitative cyclin-dependent kinase (CDK) activity between a low (S phase) and high (M phase) threshold. While this model explains the main cell cycle transitions, the importance of the temporal profile of CDK activity remains unknown. In other words, do the precise dynamics in CDK function throughout the cell cycle play a role in the integrity of cell proliferation, as was suggested by mathematical models ? Or is the two-threshold model sufficient to understand how eukaryotic cells organise their cell cycle ? Using a synthetic approach to cell cycle control in fission yeast coupled with high resolution microscopy and microfluidic technologies, our recent work reveals how CDK activity dynamics shape cell cycle progression and act as a noise filter.
      Contact : Julie SOUTOURINA <julie.soutourina cea.fr>

      Lieu : Auditorium - bâtiment 21 - Campus CNRS de Gif-sur-Yvette

      Article

  • Biologie Cellulaire

    • Vendredi 9 mars 11:00-12:00 - Damien ARNOULT - Institut André Lwoff, Villejuif, invité par Agnès Delaunay-Moisan

      A cytosolic unfolded protein response controls innate immune signaling

      Lieu : Auditorium - bâtiment 21 - Campus de Gif-sur-Yvette

      Article

    • Vendredi 16 mars 11:00-12:00 - Guy TRAN VAN NHIEU - CIRB, Paris, invité par R. Legouis

      Ca2+ signals and cytoskeletal reorganization during Shigella invasion of epithelial cells

      Résumé : The bacterial pathogen Shigella invades the colonic mucosa, triggering tissue destruction leading to the dysenteric syndrome. We will review how this pathogen promotes its invasion and intracellular replication by affecting cellular processes that regulate cytoskeletal dynamics, vesicular trafficking and the autophagy machinery. Recent findings highlighting the key role of bacterial effectors that divert host cell mechanosensing and Ca2+ signaling will be presented.

      Lieu : Bibliothèque - bâtiment 34 - campus de Gif-sur-Yvette

      Article

  • I2BC

    • Mercredi 7 mars 11:00-12:30 - Rati Fotedar - Sanford Burnham Prebys Medical Discovery Institute, San Diego, California, USA

      Braking the cell cycle : some twists and turns

      Résumé : Our contributions to the mammalian cell cycle and DNA damage fields have defined the role and mechanisms of protein modification and protein degradation in regulation of the cell cycle, DNA replication and DNA damage/repair. We have focused on proteins regulating the cell cycle (CDKs, Rb, Emi1), DNA replication (RPA, RFC, PCNA), DNA damage checkpoint (p53, p21, Emi1, WISp39, Hsp90, APC), DNA repair pathways (NER, MMR), mitosis (APC) and stress signaling (MAPK, mTOR). Our work has provided insights into the biochemical and molecular framework of DNA damage signaling by the p53 tumor suppressor as well as the role of Hsp90 and of an E3 ubiquitin ligase in this process. Cell cycle regulation is crucial for normal development, for differentiation and for tumorigenesis. I will describe recent work in which we identified a previously unknown mechanism of how CDKs regulate cell cycle progression. Finally, while cell cycle arrest is required for senescence, it is not sufficient by itself to induce this state. Our recent work reveals signals that act downstream of cell cycle arrest to induce senescence.


      Invitée par Thierry Meinnel

      Lieu : Auditorium I2BC - Bâtiment 21
      Campus de Gif-sur-Yvette

      Article

  • Microbiologie

    • Jeudi 15 mars 11:30-13:00 - Dr. Xavier Charpentier - Centre International de Recherche en Infectiologie (CIRI), Lyon

      Silently transformable : how bacteria conceal their built-in capacity of genetic exchange

      Résumé : A highly conserved DNA uptake system allows some bacteria to actively import and integrate exogenous DNA. This process, called natural transformation, represents a major mechanism of horizontal gene transfer (HGT) and is involved in the acquisition of virulence and antibiotic resistance determinants. Despite evidence of widespread HGT and the high level of conservation of the genes coding the DNA uptake system, most bacterial species appear non-transformable under laboratory conditions. This observation led us to investigated the mechanism that controls expression of the DNA uptake system in the human pathogen Legionella pneumophila (1). We found that expression of the DNA uptake system is controlled by a novel RNA-based silencing system. Silencing is relieved under specific conditions, allowing bacteria to take up free DNA and subsequently undergo genetic transformation. RNA-based silencing represents a previously unknown regulatory means to control natural transformation (2). Importantly, these findings also show that a previously overlooked family of chromosome-encoded proteins act as chaperones of trans-acting sRNAs, playing key roles in post-transcriptional gene regulation throughout bacterial species (3). Also, and in light of unpublished results, a recent hypothesis suggesting that natural transformation evolved as mechanism to rid the genome of selfish genetic elements will be discussed.
      1. Attaiech L, Boughammoura A, Brochier-Armanet C, Allatif O, Peillard-Fiorente F, Edwards RA, Omar AR, MacMillan AM, Glover M, Charpentier X. 2016. Silencing of natural transformation by an RNA chaperone and a multitarget small RNA. Proc Natl Acad Sci U S A 113:8813–8818.
      2. Attaiech L, Charpentier X. 2017. Silently transformable : the many ways bacteria conceal their built-in capacity of genetic exchange. Curr Genet 63:451–455.
      3. Attaiech L, Glover JNM, Charpentier X. 2017. RNA Chaperones Step Out of Hfq’s Shadow. Trends Microbiol 25:247–249.


      Invited by Tamara Basta-Le Berre

      Lieu : Salle Kalogeropoulos - Bâtiment 400, Campus d’Orsay

      Article

  • B3S

    • Jeudi 8 mars 10:30-12:00 - Hélène Launay - iSCB (Integrative Structural &Chemical Biology), Marseille

      Structural disorder and photosynthesis regulation deciphered using NMR, SAXS and Modelling

      Résumé : Photosynthesis is the only mean of regulation of terrestrial CO2, and its regulation is mediated via protein-protein interactions, post-translational modifications and disorder-to-order transitions. One of the central regulators of the chemical photosynthesis pathway, the Calvin-Benson-Basham cycle, is the conditionally disordered chloroplastic protein CP12. During the day, reducing conditions prevail in the chloroplast and reduced CP12 is intrinsically disordered. During the night, oxidizing conditions prevail in the chloroplast, CP12 is oxidized, and the protein binds to and inhibits to key players of the CBB cycle : glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and phosphoribulokinase (PRK). I will present our recent structural investigation of the Chlamydomonas reinhardtii CP12 using NMR, SAXS, molecular modelling, CD, which show that CP12 is a very peculiar intrinsically disordered protein that undergo several disorder-to-order transitions depending on either its redox state or its association with its partner. CP12 is a model conditionally disordered protein, and the molecular description of its disorder-to-order transitions are required to rationalize the fine tuning of photosynthesis and carbon assimilation in micro-algae.

      Lieu : Bibliothèque, Bât. 34 - Bâtiment 34, Campus Gif-sur-Yvette

      Article

  • cytoskeleton club

    • Mardi 13 mars 11:30-12:30 - Anne-Marie Pret

      Cytoskeleton club

      Résumé : Title to follow

      Lieu : Bibliothèque - Bâtiment 34, campus de Gif

      Article

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