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  • Génomes

    • Vendredi 1er décembre 11:00-12:00 - Pierre Amato - CNRS, UMR 6296, ICCF (Institut de Chimie de Clermont-Ferrand), Université Clermont Auvergne, France

      Structure and functioning of cloud microbiota

      Résumé : The atmosphere carries microorganisms and connects distant ecosystems. In addition of the underlying epidemiological issues associated with the presence of living microorganisms in the air, it was shown recently that they can contribute to atmospheric physico-chemical processes. Clouds are thus now considered in some aspects as habitats for microorganisms, albeit temporary by essence. Our first culture-based studies led on cloud microflora recovered from the atmospheric observatory at the puy de Dôme mountain summit (1465 m asl.), in the early 2000’s, revealed a high diversity in the microbial community, dominated by a few genera of bacteria and fungi. The advent of new DNA amplification methods (MDA), associated with next generation sequencing tools allows clarifying our vision of cloud biodiversity and its functioning, while overcoming the difficulties raised by the low biomass in these environments ( 104 cells m-3). Thereby, cloud water metagenomes, metatranscriptomes and amplicons libraries (16S and 18S rRNA genes) were investigated. The results showed a high taxonomic diversity in both prokaryotes and eukaryotes, but a very uneven distribution dominated by a few abundant OTUs. The large domination of Proteobacteria was confirmed, and the presence of noticeable groups such as viruses, Cyanobacteria and Archaea was observed. The active biodiversity was largely related to some groups of bacteria, notably Alpha- and Gamma-Proteobacteria. Metatranscriptomes showed a large overrepresentation of functions related to metabolic regulation, genome reorganization, access to substrates and defense against oxidants. These new pictures of cloud microbial communities indicate that these are environments open to numerous taxa, but where only a few can maintain and thus successfully disperse. They must rapidly adjust their functioning for surviving in these dynamic environments, suggesting that atmospheric transport probably operates strong selection on the microorganisms of outdoor surfaces, and thus drives to some extent microbial evolution.
      Contact : Jean-Luc Ferat <jean-luc.ferat i2bc.paris-saclay.fr>

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

      Article

    • Vendredi 8 décembre 11:00-12:00 - Olivier Espeli - Collège de France

      Dealing with environmental stresses through bacterial cell cycle contortions

      Résumé : Abstract not available
      invited by Yoshi Yamaichi <yoshiharu.yamaichi i2bc.paris-saclay.fr>

      Lieu : Salle de séminaires - bâtiment 26 (TBA) - Campus CNRS de Gif-sur-Yvette

      Article

    • Vendredi 15 décembre 11:00-12:00 - Wouter de Laat - Biomedical genomics group, Hubrecht Institute, Utrecht, The Netherlands

      Genome structure-function relationships explored at new dimensions

      Résumé : Chromatin folding is increasingly recognized as a regulator of genomic processes such as gene activity. Chromosome conformation capture (3C) methods have been developed to unravel genome topology through the analysis of pair-wise chromatin contacts and have identified many genes and regulatory sequences that, in populations of cells, are engaged in multiple DNA interactions. I will describe our contributions to this field and will present novel Multi-Contact 4C (MC-4C), that applies Oxford Nanopore long-read single molecule sequencing to study multi-way DNA conformations of individual alleles for distinction between cooperative, random and competing interactions. Using this single molecule multi-contact analysis method, we uncover previously missed structures in sub-populations of cells, reveal single locus enhancer hubs and demonstrate the collision of CTCF-anchored architectural loops. Insight into single allele higher-order topological features will help understanding how the myriad of regulatory sequences spatially coordinate their actions on individual chromosomes and facilitate interpreting the consequences of natural and induced genetic variation. If time permits, I will also discuss how we explore the application of 3C-based methods in DNA diagnostics, oncogenetics and non-invasive prenatal diagnosis.
      Contact : Daan Noordermeer <daan.noordermeer i2bc.paris-saclay.fr>

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

      Article

  • Biologie Cellulaire

    • Vendredi 1er décembre 11:00-12:00 - Stanislas TOMAVO - I2BC

      Trafic intracellulaire et biogenèse des organites sécrétoires chez Toxoplasma gondii

      Lieu : Auditorium - bâtiment 21 - campus de Gif

      Article

  • I2BC

    • Jeudi 30 novembre 11:00-12:00 - Dr Malene HANSEN - Sanford-Burnham-Prebys Medical Discovery Institute. La Jolla, USA, invited by Renaud Legouis

      Autophagy and Aging : Lessons from long-lived C. elegans

      Résumé : The cytosolic recycling process of autophagy plays an important role in many age-related diseases and has been directly linked to aging, including in the nematode C. elegans where autophagy appears beneficially induced in many conserved longevity models. As a critical process to ensure cellular homeostasis, autophagy is regulated at multiple levels, yet it remains a challenge in the field to understand how the regulation of autophagy is integrated at the cellular and molecular level to ensure health- and lifespan benefits. I will here discuss our progress on understanding the different molecular mechanisms employed by cells and organisms to regulate autophagy in response to stressors such as aging and disease.

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

      Article

  • Virologie

    • Vendredi 8 décembre 11:00-12:30 - Pierre-Yves Lozach - Université d’Heidelberg

      Early arbovirus-host cell interactions : from virus transmission to cell entry and pathogenesis

      Résumé : During natural transmission, arboviruses are introduced into vertebrate host skin through arthropod bites, and the life cycle of viruses switch from the cell biology of arthropod vectors to that of vertebrate hosts. Indeed, the cell biology in vertebrate hosts is different from that in arthropod vectors, the consequence being that arbovirus particles can change some components and the composition of their lipid and glycan coats during host switch. However it remains unclear whether host alternation is important at the molecular level for the early steps of infection and virus entry into the first-target host cells as well as the subsequent steps leading to the pathogenesis. Within this talk, these issues will be addressed based on the analysis of the phleboviruses Rift Valley fever and Uukuniemi in arthropod vector and mammalian host cells by state-of-the-art fluorescence-based techniques in fixed and living cells.

      Lieu : Salle de séminaires bâtiment 14C - Bât. 14C
      Campus Gif-sur-Yvette

      Article

  • B3S

    • Mardi 28 novembre 11:00-12:00 - Prof. Jurgen Sygusch - Professeur titulaire, Biochimie, Université de Montréal

      Aspects mécanistiques et fonctions ’moonlighting’ de l’enzyme glycolytique aldolase

      Résumé : La fructose-bis phosphate aldolase est un enzyme essentiel de la glycolyse et des fonctions cellulaires. L’enzyme démontre une stéréospécificité exquise envers son substrat. Dans la direction de la gluconéogenèse, l’enzyme catalyse la synthèse de son substrat chiral à partir des réactifs achiraux. Le mécanisme réactionnel préconisé par l’enzyme qui produira le diastéréoisomère, fructose-bisphosphate, à partir des triose-Ps achiraux sera le sujet de la conférence. Les enzymes glycolytiques sont bien connus pour leurs rôles de ‘moonlighting’ où il interagit avec d’autres protéines intracellulaires en modifiant leurs fonctions. Dans le cas de l’aldolase, l’enzyme exerce un rôle important dans le maintien du cytosquelette et son inhibition a un effet fortement inhibiteur sur la croissance des cellules cancérigènes. Comment l’inhibition de l’enzyme aldolase se traduit-elle par l’apoptose des cellules cancérigènes sera également le sujet de la conférence.

      Lieu : Salle Lederer - Bâtiment 430
      Campus d’Orsay

      Article

    • Mercredi 29 novembre 10:30-11:30 - Dr Sonia LONGHI - Lab. AFMB, CNRS & Aix-Marseille University, Marseille, France

      The interplay between order and disorder in the replicative complex of paramyxoviruses

      Résumé : In the course of the structural characterization of the nucleoproteins (N) and phosphoproteins (P) from three paramyxoviruses (e.g. measles, Nipah and Hendra virus) we discovered that they contain long disordered regions. The N and P proteins from these viruses thus provide an excellent model system to study the functional impact of disordered motifs. The non-segmented, single-stranded RNA genome of these paramyxoviruses is encapsidated by the nucleoprotein (N) within a helical nucleocapsid. Transcription and replication are carried out onto this ribonucleoproteic complex by the viral RNA dependent RNA polymerase that consists of a complex between the large protein (L) and the phosphoprotein (P). The P protein serves as an essential polymerase co-factor as it allows recruitment of L onto the nucleocapsid template. Tethering of L relies on the interaction between the C-terminal X domain (PXD) of the P protein and the C- terminal, intrinsically disordered domain (NTAIL) of N. This latter is disordered not only in isolation but also in the context of the nucleocapsid, being partly exposed at the surface of this latter. Within NTAIL, a short motif, serving as molecular recognition element (MoRE), has been identified and the mechanisms of its interaction with PXD thoroughly investigated. In its free from, the MoRE is partly pre-configured as an α-helix. Binding to PXD triggers stable α-helical folding of this motif, while the majority of NTAIL remains “fuzzy”. Beyond PXD, measles virus NTAIL also binds the major inducible heat shock protein 70 (hsp70). Although NTAIL binds hsp70 through the same motif involved in binding to PXD, the binding mechanisms are not the same, which constitutes an illustrative example of partner-mediated polymorphism of an intrinsically disordered protein and of the relative insensitiveness of the bound structure to the pre-recognition state.
      In my talk, I will focus on measles virus NTAIL and will summarize the main results we obtained so far. In particular, I will focus on the mechanistic and functional aspects of the interactions established by NTAIL and will highlight the functional implications of disorder for viral transcription and replication.
      Choice of five selected references
      1. Longhi et al (2017) Cell. Mol. Life Sci. 74, 3091–3118
      2. Bloyet LM et al (2016) Plos Pathogens 12(12):e1006058.
      3. Longhi S. (2015) FEBS Lett. 589, 2649-59.
      4. Dosnon et al (2015) ACS Chem. Biol. 10, 795−802
      5. Habchi J et al (2014) Chem. Rev. 114, 6561-88.

      Lieu : Bibliothèque - Bâtiment 34, Campus de Gif

      Article

  • cytoskeleton club

    • Mardi 12 décembre 11:30-12:30 - Delphine Gogendeau

      Cytoskeleton club

      Résumé : Down-regulation of different transition zone proteins in Paramecium induces antagonistic effects on cilia stability

      Lieu : Bibliothèque - Bâtiment 34, campus de Gif

      Article

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  • I2BC

    • Vendredi 8 décembre 09:00-17:00 -

      YOUR-Carreer day

      Lieu : Auditorium - Bâtiment 21, campus de Gif

      Article

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