Neuvième réunion annuelle du GdR Architecture et Dynamique Nucléaires (ADN)

Abstracts et diapos des présentations

51. 3D genome organization and the genetic risk to (some) diseases

Annick Lesne (CNRS)

Présentation orale

Genome-wide association studies have established statistical associations between various diseases and a large number of single-nucleotide polymorphisms (SNPs). However, they provided no simple explanation of the mechanisms underlying this association.  
Following the idea that 3D genome organization and its variations may have a functional role in gene regulation, we investigated the...

52. Chromosome structure due to phospho-mimetic H2A modulates DDR through increased chromatin mobility

Emmanuelle FABRE (CNRS)

Présentation orale

In budding yeast and mammals, double strand breaks trigger global chromatin mobility together with the rapid phosphorylation of the histone H2A over an extensive region of the chromatin. To assess the role of H2A phosphorylation in this response to DNA damage, we have constructed strains where H2A has been mutated to the phospho-mimetic H2A-S129E. We show that H2A-S129E mutant increases global...

45. Cohesin-mediated chromatin folding constrains homology search during DNA repair

Dr HELENE BORDELET ( Régulation spatiale des génomes, Institut Pasteur, CNRS UMR3525, 75015 Paris, France / Univ Lyon, ENS, UCBL, CNRS, INSERM, Laboratory of Biology and Modelling of the Cell, UMR5239, U 1210, F-69364, Lyon, France)

Présentation orale

DNA break repair by homologous recombination (HR) entails a search for homology carried out by a specialized nucleoprotein filament (NPF). The search mechanism remains elusive, notably its interplay with the folding of chromatin in the nucleus. We show in the tractable model system S. cerevisiae that it takes place in the reorganized context of individualized metaphase-like chromosomes...

50. Euryarchaeal genomes are organised into domains and chromatin loops but lack transcription-mediated compartmentalization

Charlotte Cockram (Institut Pasteur, Unité Régulation Spatiale des Génomes, CNRS UMR 3525, F-75015 Paris, France)

Présentation orale

Chromosome conformation capture (3C/Hi-C)-based methods have been used extensively to probe the average 3D organization of genomes, revealing fundamental aspects of chromosome dynamics. However, when applied to prokaryotic and archaeal species the current protocols are expensive, inefficient, and limited in their resolution. We developed a cost-effective approach that allows the exploration of...

47. Folding and persistence times of intramolecular G-quadruplexes transiently embeded in a DNA duplex

Phong Lan Thao Tran

Présentation orale

G-quadruplex (G4) DNA structures have emerged as important regulatory elements during DNA metabolic transactions. Most in vitro studies have focused so far on the G4 kinetics within single-stranded DNA. However, G4 structures potentially form in genome regions where their stability is challenged by a complementary strand. Since the energy of hybridization of Watson-Crick structures dominates...

53. Genomic contacts reveal the control of sister chromosome decatenation in E. coli

Brenna Conin (Institut Pasteur, College de France)

Présentation orale

In E. coli, Topoisomerase IV is responsible for the untangling of catenanes that are formed during the replication of the chromosome and has been shown to play an essential role in nucleoid segregation. Previous studies have shown that alterations in Topo IV result in a prolonged interaction between sister chromosomes leading to poor chromosome segregation and a loss ...

43. Global and ancestral regulation by DNA supercoiling is tuned by promoters’structure

Raphaël Forquet (MAP - UMR5240 - CRP Team)

Présentation orale

Usual models of transcriptional regulation are centered on transcription factors, which recognize specific sequences in genes’ promoters. However, at a more global scale, the physical state of the double helix, embedded in the chromatin fibre, plays a crucial role in genes’ expression in vivo. In particular, torsional stress (or DNA supercoiling) is an ubiquitous feature in DNA transactions,...

55. Live imaging and biophysical modelling support a button-based mechanism of somatic homolog pairing

Daniel Jost (CNRS TIMC-IMAG)

Présentation orale

The spatial configuration of the eukaryotic genome is organized and dynamic,
providing the structural basis for regulated gene expression in living cells. In Drosophila melanogaster , 3D genome organization is characterized by the phenomenon of somatic homolog pairing, where homologous chromosomes are intimately paired from end to end. While this organizational principle has been recognized...

44. NUCLEOSOME CONFORMATIONAL VARIABILITY IN VITRO & IN SITU EXPLORED BY CRYO-ELECTRON MICROSCOPY AND TOMOGRAPHY OF VITREOUS SECTIONS

Amélie Leforestier (CNRS, Laboratoire de Physique des Solides)

Présentation orale

In most eukaryotic cells, DNA is packed into the chromatin « bead on string » filament of nucleosomes, formed by 145–147 bp DNA wrapped into 1.65 turns of a left-handed superhelix around a histone octamer. Atomic resolution structures have been obtained from X-ray crystallography, and more recently from cryo-EM of identical, symmetric and highly stable engineered particles, which has led,...

54. Semi-analytical modeling of chromatin loop-extrusion

Vittore Scolari

Présentation orale

At the scale of 10^5-10^6 base pairs, human chromosomes are structured in topologically associated domains (TADs). These are regions of the chromosome within which contacts are more frequent that with adjacent regions, as measured by 'chromosome conformation capture' experiments such as Hi-C. TADs have been shown to result from the action of cohesin, a molecular motor. Cohesin binds to...

57. SETDB1 dependent H3K9me3/H3K36me3 dual chromatin regulate cell differentiation by restricting enhancers

Amandine BARRAL ({UNIV MONTPELLIER}UMR9002)

Présentation orale

Cellular identity is conferred by specific gene expression profiles that are regulated by transcription factors and chromatin. Combination of specific histone modifications characterize gene activity. Active genes typically display an enrichment in histone H3 lysine 4 trimethylation (H3K4me3) at their promoters, whereas SET Domain 2 (SETD2) trimethylates histone H3 lysine 36 (H3K36me3) in...

56. Smc3 acetylation anchors cohesin dependent chromatin loops

Nathalie BASTIE ({UNIV TOULOUSE PAUL SABATIER}UMR5099)

Présentation orale

Past decade has shown that the cohesin is essential for the regulation of mammalian’s genomes 3D organization. Cohesin is a ring-shaped complex that interacts with three related hook-shaped proteins composed of HEAT repeats namely Pds5, Scc3/STAG and Scc2/Nipbl that regulate its functions. Cohesin shapes mammalian genomes by establishing chromatin loops along chromosomes, most likely through...

46. The development of Nano-C allows the characterization of TAD boundaries with unprecedented resolution

Li-Hsin Chang (Institut de Biologie Integrative de la Cellule)

Présentation orale

Chromosome conformation capture (3C) methods are a powerful tool for uncovering 3D genome organization. Short-read Illumina sequencing restricts 3C to the description of average conformations within large cell populations. Significant variation between individual cells within the same population may be present though. For instance, if different contacts happen simultaneously, exclusively, or...

48. The histone variant H3.3 and its chaperone DAXX preserve heterochromatin integrity of embryonic pluripotent cells.

Pierre Therizols (UMR INSERM 944, CNRS 7212)

Présentation orale

Within the nucleus, heterochromatin domains segregate in particular compartments such as the chromocenters that contain pericentromeric heterochromatin (PCH) regions, or the lamina-associated domains (LADs) that localize at the periphery of the nucleus. In most cell types, DNA methylation is essential for heterochromatin formation, directly contributing to the transcriptional repression of DNA...

58. Transcriptomic response of phytopathogen Dickeya dadantii to an increase of DNA supercoiling by novel antibiotic seconeolitsin

Maïwenn Pineau

Poster

DNA supercoiling, i.e., the presence of torsional stress in the DNA double helix, is an essential mechanism of bacterial chromosome compaction and affects gene expression. Supercoiling level is mainly regulated by topoisomerase I and DNA gyrase. Inhibiting one of these enzymes with an antibiotic leads to a global supercoiling modification and global gene expression changes. Novobiocin, an...

49. Visualisation 3D des séquences répétées dispersées du génome humain.

Christophe Escudé (Muséum National d'Histoire Naturelle)

Présentation orale

L’architecture tridimensionnelle des génomes eucaryotes joue un rôle important dans leur régulation fonctionnelle. Le développement de méthodes de capture de la conformation chromosomique, telles que le Hi-C, a mis en évidence l'existence de deux compartiments appelés A et B, séparés dans l'espace, qui correspondent respectivement à l'euchromatine (gènes exprimés) et à l'hétérochromatine...