topIb, a phylogenetic hallmark gene of Thaumarchaeota encodes a functional eukaryote-like topoisomerase IB

International audienceType IB DNA topoisomerases can eliminate torsional stresses produced during replication and transcription. These enzymes are found in all eukaryotes and a short version is present in some bacteria and viruses. Among prokaryotes, the long eukaryotic version is only observed in archaea of the phylum Thau-marchaeota. However, the activities and the roles of these topoisomerases have remained an open question. Here, we demonstrate that all available thaumar-chaeal genomes contain a topoisomerase IB gene that defines a monophyletic group closely related to the eukaryotic enzymes. We show that the topIB gene is expressed in the model thaumarchaeon Ni-trososphaera viennensis and we purified the recom-binant enzyme from the uncultivated thaumarchaeon Candidatus Caldiarchaeum subterraneum. This enzyme is active in vitro at high temperature, making it the first thermophilic topoisomerase IB characterized so far. We have compared this archaeal type IB enzyme to its human mitochondrial and nuclear counterparts. The archaeal enzyme relaxes both negatively and positively supercoiled DNA like the eukaryotic enzymes. However, its pattern of DNA cleavage specificity is different and it is resistant to camptothecins (CPTs) and non-CPT Top1 inhibitors, LMP744 and lamellarin D. This newly described ther-mostable topoisomerases IB should be a promising new model for evolutionary, mechanistic and structural studies

Yves-Michel Metman (1913-1999)

Delmas Marie-Claude, Neirinck Danièle. Yves-Michel Metman (1913-1999). In: Bibliothèque de l'école des chartes. 2001, tome 159, livraison 2. pp. 712-715

Influence du taux protéique de la ration sur la composition corporelle du lapin

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Yves-Michel Metman (1913-1999)

Delmas Marie-Claude, Neirinck Danièle. Yves-Michel Metman (1913-1999). In: Bibliothèque de l'école des chartes. 2001, tome 159, livraison 2. pp. 712-715

BODY COMPOSITION AND DEGREE OF WEIGHT MATURITY IN RABBITS OF SEVERAL GENOTYPES

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Utilisation de pellicules de colza dans l'alimentation du lapin en croissance. II. - Effet sur la qualité des carcasses

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A STUDY OF MUSCULAR GROWTH IN RABBITS OF THREE GENOTYPES : ROLE OF NUCLEAR MULTIPLICATION AND CELL-SIZE INCREASE

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STUDY OF GENETIC VARIATION IN RABBIT MUSCLE pH MEASURED AFTER SLAUGHTER

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