IJM News since 2010

  • A multi-faceted enzyme silences repeats in the genome

    In plants and animals, histone proteins bind to DNA and carry different chemical modifications, which can repress the expression of genes or of mobile genetic elements. Sandra Duharcourt’s team characterized the properties of an unconventional enzyme in the unicellular eukaryote Paramecium, which catalyses two distinct silent histone modifications and silences genomic repeats. This work published in Nature Communications reveals that these two modifications share a common ancestral role in keeping silent transposable elements.

  • Le prix Nicloux 2019 a été attribué à Odil Porrua

    La Société Française de Biochimie et Biologie moléculaire a remis le Prix Maurice Nicloux 2019 à Odil Porrua, chargée de recherche CNRS, membre de l'Institut Jacques Monod. Odil Porrua s’intéresse depuis le début de sa carrière à différents aspects de l’expression des gènes. De 2005 à 2009, Odil a effectué sa thèse dans le laboratoire de E. Santero (Espagne) où elle a étudié la régulation de certains gènes impliqués dans la dégradation de molécules contaminantes chez la bactérie.En 2009, Odil a rejoint le laboratoire de Domenico Libri, d’abord au Centre de Génétique Moléculaire (Gif sur Yvette) puis à l’Institut Jacques Monod (Paris) à partir de 2013. D’abord comme post-doc puis comme chercheur CNRS, Odil a conduit plusieurs projets autour du métabolisme des ARN non-codants chez la levure. Notamment par des approches biochimiques et structurales, elle a pu dévoiler les mécanismes de terminaison de la transcription non-codante qui étaient alors très peu connus. Deux ans après avoir obtenu son poste de chercheur CNRS, en 2014, et grâce à un financement ANR JCJC, Odil a abordé l’étude du rôle de la terminaison de la transcription dans la régulation de l’expression de gènes.

  • June 2019 : Chromatin condensation fluctuations rather than steady-state predict chromatin accessibility

    Chromatin accessibility to protein factors is critical for genome activities. However, the dynamic properties of chromatin higher-order structures that regulate its accessibility are poorly understood. Researchers from the team “mechanotransduction: from cell surface to nucleus” took advantage of the microenvironment sensitivity of the fluorescence lifetime of EGFP-H4 histone incorporated in chromatin to map in the nucleus of live cells the dynamics of chromatin condensation and its direct interaction with a tail acetylation recognition domain (the double bromodomain module of human TAFII250, dBD). They revealed chromatin condensation fluctuations supported by mechanisms fundamentally distinct from that of condensation. Fluctuations are spontaneous, yet their amplitudes are affected by their sub-nuclear localization and by competing mechanisms dependent on histone acetylation, ATP and both. Moreover, accessibility of acetylated histone H4 to dBD is not restricted by chromatin condensation nor predicted by acetylation, rather, it is predicted by chromatin condensation fluctuations.

  • March 2019: Is the replication timing control constant through S phase?

    Before each cell division, the full genome has to be entirely and faithfully duplicated thereby each daughter cell inherits the complete genetic information. This duplication occurs under the control of a highly sophisticated replication program during the restricted time period corresponding to S phase. DNA replication is initiated at a large number of sites, known as origins of replication, on the chromosomes of eukaryotic cells. In one individual cell, only a part of the origins licensed in G1 phase are activated during S phase thus illustrating the flexible origin choice which is directly related to the stochastic nature of the eukaryotic replication program. Another particularity of the program is that origin activation is also subject to temporal regulation. Like this, some domains of hundred kilobases are replicated in early S phase, others are replicated in mid S phase and the remainders in late S phase. This temporal control is very strict. To date, the factors responsible for the establishment, regulation and maintenance of these domains throughout the cell cycle remain largely unknown. As a first step towards a better comprehension of this temporal program, the team of MN Prioleau has investigated whether the stochasticity of the timing program is changing along the S phase.

  • January 2019: when Transcription Meets Replication

    Conflicting activities necessary for the expression, the maintenance and the propagation of genomes need to be coordinated. Just like one's liberty to swing fists ends where another's nose begins, coordination is achieved through a tight control of where and when directly opposed activities take place. In a study published recently in eLife, researchers from the Libri team are now showing that replication factors generally "protect" sites where replication initiates by terminating incoming transcription, and that the low levels of transcription that enter origins of replication affect their firing efficiency.

  • January 2019 : Cell shape changes and cytoskeleton adaptation to migrate into complex environments

    Cell migration is an essential biological process that drives tissue and organ formation during embryo development, and also helps protect the body through immune response and wound healing mechanisms.

  • January 2019: General Regulatory Factors: guardians of transcription fidelity

    What is a transcription factor? Classical biology tells us that a transcription factor binds to a promoter and activates (or represses) gene expression by promoting (or inhibiting) the initiation of transcription. What about transcription factors that activates gene expression by inhibiting initiation?

  • Deciphering how the geometrical and mechanical context impacts actin filament disassembly

    In an article recently published in P.N.A.S., researchers from the “Regulation of Actin Assembly Dynamics” team at Institut Jacques Monod show how the biochemical disassembly of actin filaments can be modulated by their physical context.

  • January 2019: Links between polarity protein localization, membrane trafficking and the cytoskeleton

    Cellular polarity is an essential characteristic of the development and functioning of an organism. It allows the subdivision of the cell into different functional domains, both at the level of the plasma membrane and the cytoplasm, ensuring asymmetry in the functions of the cell. Establishment and maintenance of cell polarity are under the control of two main well preserved protein modules among metazoans, including PAR1 and PAR3, respectively.

  • 29 décembre 2018 : décès de Jacques Ricard

    C’est avec un grand regret que nous avons appris le décès le 29 décembre dernier de Jacques Ricard qui fut directeur de l’Institut Jacques Monod de 1992 à 1996 et professeur d’Enzymologie à l’Université Paris-Diderot. Il a été également directeur du Centre de Biochimie et de Biologie Moléculaire du CNRS à Marseille de 1980 à 1991, membre de l’Académie Internationale de Philosophie des Sciences et membre correspondant de l’Académie des Sciences. Nous lui devons en particulier d’avoir structuré l’Institut Jacques Monod en départements, qui fut le mode de fonctionnement jusqu’en 2008 et d’avoir été l’artisan d’une orientation « Biologie cellulaire » forte à l’Institut. Ses travaux ont été fondateurs dans le domaine de l’enzymologie, notamment en ce qui concerne la régulation des enzymes via leurs interactions avec leurs substrats et métabolites ainsi que leur environnement cellulaire.

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