Topo-Club 2016

Liste des contributions

5. A DNA topoisomerase VI-like complex initiates meiotic recombination

Mathilde Grelon (INRA)

The SPO11 protein catalyzes the formation of meiotic DNA double strand breaks (DSBs) and is homologous to the A subunit of an archaeal topoisomerase (topo VI). Topo VI are heterotetrameric enzymes composed of two A and two B subunits, however no topo VIB involved in meiotic recombination had been identified. Here, we characterized a structural homolog of the archaeal topo VIB subunit (MTOPVIB,...

2. DNA double-strand breaks induced by transcription-blocking topoisomerase I lesions

Dr Olivier Sordet (CRCT-INSERM UMR1037)

Topoisomerase I (Top1) relaxes DNA supercoiling generated during transcription by producing transient Top1-DNA cleavage complexes (Top1cc). These Top1cc intermediates can be stabilized under a broad range of physiological conditions including oxidative base damage, alkylation by carcinogenic compounds and nicks, and by ribonucleotide misincorporation. Stabilized Top1cc are potent...

3. DNA minicircles are new tools to study in vitro retroviral integration

Dr Marc LAVIGNE (Institut Pasteur, Paris)

Integration is an essential step of retroviral replication and a promising anti-HIV target. It is performed by a viral-encoded enzyme, integrase (IN), and the selectivity of this enzyme for the target cellular DNA is important for retroviral replication. Genetic, biochemical and structural studies have revealed a role of cellular chromatin in this selectivity but the underlying molecular...

4. DNA supercoiling activity of DNA gyrases from Francisella strains resistant to quinolones

Dr Patricia RENESTO (CNRS)

Quinolones are one of the most commonly prescribed classes of antibacterials agents in the world and are used to treat several bacterial infections in humans. Accordingly, microbiological and clinical data showed that ciprofloxacin, and possibly other fluoroquinolones represent an efficient first-line treatment for oral therapy of tularemia, a disease caused by the Gram negative bacterium...

0. Effects of genome position of supercoiling-dependent gene expression

Dr Bianca Sclavi (LBPA, UMR 8113)

Global transcription regulators are factors that can influence the activity of several bacterial promoters and can thus play a key role during bacterial adaptation to a change in growth environment. These factors include small metabolites, such as ppGpp, abundant nucleoid-associated proteins and DNA topology. The latter two are not equally repartitioned throughout the genome and could thus...

7. Genome mechanics: let's talk about figures

Dr Christophe Lavelle (CNRS)

We wish here to emphasize some physical characteristics of genome organization in order to provide a concrete and quantitative framework in which to interpret DNA metabolism events such as transcription or replication. Indeed, as various molecular motors push, pull and twist DNA, transient forces and torques develop within chromatin, with expected regulatory consequences. How much? How fast?...

1. Identification des modifications post-traductionnelles de l'histone H3 impliquées dans la condensation des chromosomes "in embryo"

Dr Nathalie Beaujean (INRA)

Epigenetic modifications and nuclear architecture are globally rearranged after fertilization. Unlike somatic cells, mammalian embryos for example present a unique organization of pericentromeric heterochromatin. In mouse embryos, this part of the heterochromatin is not organized in clusters but in spherical structures around nucleolar precursor bodies forming a ‘‘cartwheel’’. This pericentric...

10. Mapping Topoisomerase IV binding and activity sites on the E. coli genome

M. Hafez EL Sayyed (Chromosome Dynamics Lab,CIRB - Collège de France)

Catenation links between sister chromatids are formed progressively during DNA replication and are involved in the establishment of sister chromatid cohesion. Topo IV is a bacterial type II topoisomerase involved in the removal of catenation links both behind replication forks and after replication during the final separation of sister circular chromosomes. We have investigated the global...

9. Phylogenies of type II and type IB DNA topoisomerases

Dr Patrick Forterre (Institut Pasteur & I2BC Paris Saclay)

We have updated the phylogenies of type II and type IB DNA topoisomerases (for previous ones, see Forterre et al., Biochimie, 2007, Brochier-Armanet et al., Biology Direct, 2008). Our results suggest that eukaryotic type II could have originated from Large NucleoCytoplasmic DNA viruses (NCLDV). In the case of type IB DNA topoisomerases, we observed that some NCLDV encode the short form typical...

11. Polymer model of supercoiled molecules including multiple structural forms of DNA

Dr Thibaut Lepage (TIMC-IMAG, Université Joseph Fourier, CNRS UMR 5525, Grenoble)

DNA supercoiling lies at the core of transcriptional regulation. Except for a few cases, capturing its impact in vivo remains elusive, though. Supercoiling is indeed distributed in a non-trivial way between twist, writhe (plectonemes) and change of structural forms of DNA (including denaturation) and depends, a priori, on genomic sequences. In this talk, we will present a polymer model of DNA...

6. The TopoVIB-Like protein family is required for meiotic DNA double strand break formation

M. bernard de Massy (Institut de Génétique Humaine)

Meiotic recombination is induced by the formation of DNA double strand breaks (DSBs) catalyzed by SPO11, the ortholog of the subunit A of TopoVI DNA topoisomerase (TopoVIA). TopoVI activity requires the interaction between A and B subunits; however whether SPO11 functions alone or through association with another subunit has remained an open question for the last 18 years. Here, we identified...