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1er février 2019: 1 événement

  • Département Biologie des Génomes

    Vendredi 1er février 11:00-12:00 - Eugene Gladyshev - Institut Pasteur

    Recombination-independent recognition of DNA homology for meiotic silencing in Neurospora crassa

    Résumé : Homologous chromosome pairing represents a critical aspect of meiosis in nearly all sexually reproducing organisms. While in some species this process depends on the formation of double-strand DNA breaks, in the others it can proceed (partially or completely) in the apparent absence of DNA breakage and recombination. The nature of a mechanism that can identify intact homologous chromosomes represents a fundamental question in molecular biology. Using “meiotic silencing by unpaired DNA” (MSUD) in Neurospora crassa as a model system, we demonstrate the existence of a cardinally new solution to the problem of DNA homology recognition during meiosis. Here we take advantage of the unique ability of MSUD to detect and silence (by RNA interference) any relatively short fragment of genomic DNA present on only one of the two homologous chromosomes. Specifically, we show that MSUD does not require the function of eukaryotic RecA proteins (Rad51/Dmc1) and the type II topoisomerase-like protein Spo11. We further show that MSUD can recognize patterns of weak interspersed homology in which triplet units of sequence identity are arrayed with a periodicity of 11 base-pairs. In doing so, MSUD shares its basis for homology recognition with “repeat-induced point mutation” (RIP), a prototypical genome-defense phenomenon that is activated in premeiotic nuclei of N. crassa and many other filamentous fungi. Taken together, these results reveal the role of a recombination-independent homology-directed process in guiding the expression of small interfering RNAs and, more broadly, suggest that meiotic chromosomes can be evaluated for homology at the base-pair resolution by a mechanism that operates on intact DNA double helices.
    Contact : Fabienne Malagnac <fabienne.malagnac u-psud.fr>

    Lieu : Salle Kalogeropoulos - Bât. 400 - Campus d’Orsay

    En savoir plus : Département Biologie des Génomes