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  • Génomes

    • Vendredi 4 octobre 11:00-12:00 - Johan DECELLE - Plant and Cell Physiology lab, Université Grenoble

      Algal farming in planktonic symbiosis through structural and metabolic transformation

      Résumé : Photosymbiosis between single-celled hosts and microalgae is widely distributed in the oceanic plankton. However, the functioning of this ecologically-important interaction remains enigmatic, particularly the mechanisms that allow the host cell to exploit its intracellular microalgae. Here, using a combination of single-cell structural (3D electron microscopy) and chemical imaging (nanoSIMS, synchrotron X-ray fluorescence), we show how the host reconfigures the photosynthetic machinery and metabolism of its microalgae. Within the host, photosynthetic efficiency is enhanced and the volume of algal cells increases up to ten times with a higher number of chloroplasts. Subcellular mapping of nutrients and N/P ratios shows that symbiotic microalgae are limited in phosphorous, and are transformed into an energy-acquisition machinery. The host also supplies a substantial amount of metals (iron and cobalt) that are stored in high concentration in algal vacuoles. Overall, this study sheds the light on host mechanisms to engineer microalgae in the oceanic plankton. In the near future, we plan to conduct transcriptomics, proteomics and metabolomics studies to better understand the symbiotic interaction, and compare with other photosymbiosis models in freshwater habitats, such as the ciliate Paramecium with the green alga Chlorella.


      Contact : Mireille BETERMIER (mireille.betermier i2bc.paris-saclay.fr)

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

      Article

    • Vendredi 18 octobre 11:00-12:00 - Heath MURRAY - Newcastle University, Royaume Uni

      Identification of a basal system for bacterial chromosome origin unwinding

      Résumé : Genome duplication is essential for cell proliferation and DNA synthesis is generally initiated by dedicated replication proteins at specific loci termed origins. In bacteria the master initiator DnaA binds the chromosome origin (oriC) and unwinds the DNA duplex to permit helicase loading. However, despite decades of research it remained unclear how the information encoded within oriC guides DnaA-dependent strand separation. To address this fundamental question, we took a systematic genetic approach in vivo and identified the core set of essential sequence elements within the Bacillus subtilis chromosome origin unwinding region. Using this information we then show in vitro that the minimal replication origin sequence elements are necessary and sufficient to promote the mechanical functions of DNA duplex unwinding by DnaA. Because the basal DNA unwinding system characterized here appears to be conserved throughout the bacterial domain, this discovery provides a framework for understanding oriC architecture, activity, regulation and diversity.


      Contact : Jean-Luc FERAT (jean-luc.ferat i2bc.paris-saclay.fr)

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

      Article

  • Biologie Cellulaire

    • Jeudi 10 octobre 12:00-13:00 - Agnès RÖTIG - Institut des maladies génétiques Imagine, Paris

      Comment des dysfonctions mitochondriales modifient le trafic intracellulaire (frataxine ou NBIA et dérégulation du fer cytosolique) ?

      Résumé : Réunion du Club "Mitochondrie"

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

      Article

    • Vendredi 11 octobre 11:30-12:30 - Paola DEFILIPPI - Dept. of Molecular Biotechnology and Health Sciences, MBC, University of Torino, Italie

      The scaffold protein p140Cap as a molecular hub for limiting cancer progression : a paradigm in breast cancer and neuroblastoma.

      Résumé : The p140Cap adaptor protein, encoded by the SRCIN1 gene, is a scaffold molecule physiologically expressed in few epithelial tissues, such as the mammary gland, and in neurons. However, p140Cap is also expressed in a significant subset of breast cancers and neuroblastoma tumors. In the subgroup of ERBB2-amplified breast cancers, a high p140Cap status predicts a lower probability of developing a distant event and a clear difference in survival. In the neuroblastoma tumors, SRCIN1 mRNA levels are an independent risk factor inversely correlated to disease aggressiveness. In both tumor models, p140Cap is causal in dampening tumor cell progression, impairing in vivo tumor growth, and resulting in decreased spontaneous metastasis formation. By a combination of biochemical and molecular approaches, and through the analysis of the p140Cap interactome and the related signaling pathways, we dissect how common and specific mechanisms may contribute to p140Cap ability to limit cancer progression.

      Lieu : Bibliothèque - bâtiment 34 - campus de Gif

      Article

  • B3S

    • Vendredi 4 octobre 11:00-12:00 - Ji-Shen ZHENG - University of Science and Technology of China, Hefei, China

      Chemical synthesis of membrane proteins and their biological applications

      Résumé : Chemical protein synthesis may enable the preparation of proteins with predesigned structures at atomic precision, thus permitting the acquisition of otherwise difficult-to-obtain proteins bearing either post-translational modification or site-specific labeling for advanced studies. Chemical synthesis of water-soluble globular proteins has been well developed and applied to biochemical and pharmaceutical studies.
      Membrane proteins are responsible for the substance transport, information exchange and enzyme catalysis, and are critical for cell growth and development, immune response and other processes. However, the highly important class of membrane proteins such as multiple membrane-spanning ion channels and drug transporters remains challenging to chemical synthesis owing to their hydrophobic nature and tendency to form aggregates.
      To overcome the problem, we developed the removable backbone modification (RBM) strategy for the chemical synthesis of membrane proteins. The RBM-modified membrane protein segments behave almost the same as ordinary water-soluble peptides in terms of Fmoc solid-phase synthesis, ligation, purification, and mass spectrometry characterization. The solubilizing RBM is straightforward to install at all amino acid sites except proline during the synthesis of transmembrane regions and facile to remove once synthesis of the peptide is complete.
      The RBM strategy was successfully prepared a series of difficult-to-obtain membrane proteins by biological expression method or membrane protein probes labeled with isotopes or fluorescence, including : (1) the homotetramer Kir5.1 ion channel transmembrane domain with K+ conductivity ; (2) the site-specific isotope-labeled hepatitis C virus ion channel p7 ; (3) the post-translationally modified membrane proteins (e.g. S-palmitoylated sarcolipin and M2 ion channel from Influenza A virus). These custom-made membrane protein samples provide unique molecular tools for the study of their structure, function and mechanism of action.
      For information, please contact, Nadège Jamin, Véronica Beswick or Cédric Montigny (I2BC / B3S / LPSM)

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

      Article

  • cytoskeleton club

    • Mardi 8 octobre 11:30-12:30 -

      Cytoskeleton club - canceled

      Lieu : Bibliothèque - bât. 34

      Article

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