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7 décembre 2018: 1 événement

  • Département Biologie des Génomes

    Vendredi 7 décembre 11:00-12:30 - Arjan de Groot - UMR 7265 CEA-CNRS-AMU, CEA Cadarache

    Radiation and oxidative stress resistance mechanisms in Deinococcus species : regulation and diversity

    Résumé : Deinococcus bacteria are extremely resistant to gamma radiation and other oxidative stress- and DNA damage-generating conditions. Among these bacteria, Deinococcus radiodurans has been studied most extensively, and the numerous data indicate that its extreme resistance results from a combination of multiple factors and well-regulated mechanisms that limit oxidative protein damage and enable repair of massive DNA damage.
    We are studying Deinococcus deserti using various approaches. One discovery was the exceptionally high proportion of leaderless mRNAs (i.e. lacking a 5’-untranslated region and Shine-Dalgarno sequence), including novel leaderless transcripts for small peptides (1). We also described a novel radiation response mechanism involving two proteins : a transcriptional repressor of DNA repair genes that is cleaved and inactivated be a specific, constitutively expressed metalloprotease (2). This SOS-independent response is crucial for radiation resistance. Recent data concerning the molecular mechanism by which radiation triggers repressor cleavage and gene induction will be presented (activation of the metalloprotease ; 3D structure of the repressor). The metalloprotease/repressor pair is highly conserved in different Deinococcus species. However, there is diversity in the set of genes regulated by these proteins (3). This observation stimulated us to search and compare more than 250 other radiation and oxidative stress resistance-associated proteins in the genomes of 11 radiation-resistant Deinococcus species. Strikingly, this revealed a large diversity of proteins involved in DNA repair (e.g. novel two-domain proteins) and oxidative stress defence, and in their regulation, even within the Deinococcus genus (4).
    (1) Genome Biol Evol 2014 ; 6:932–48. (2) Mol Microbiol 2014 ; 94:434–49. (3) MicrobiologyOpen 2017 ; 6:e477. (4) FEMS Microbiol Rev 2018/2019 ; doi : 10.1093/femsre/fuy037.

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

    En savoir plus : Département Biologie des Génomes