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Genre/Form: | Thèses et écrits académiques |
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Material Type: | Document, Thesis/dissertation |
Document Type: | Computer File |
All Authors / Contributors: |
Andrea Frapporti; Sandra Duharcourt; Slimane Ait-Si-Ali, biologiste).; André Verdel; Valérie Robert; Sophie Polo; Université Sorbonne Paris Cité.; École doctorale Bio Sorbonne Paris Cité (Paris / 2014-....).; Institut Jacques Monod (Paris).; Université Paris Diderot - Paris 7 (1970-2019). |
OCLC Number: | 1226474006 |
Notes: | Titre provenant de l'écran-titre. |
Description: | 1 online resource |
Responsibility: | Andrea Frapporti ; sous la direction de Sandra Duharcourt. |
Abstract:
Eukaryotic genomes are organized into chromatin, a complex nucleoprotein structureessential for the regulation of gene expression and for maintaining genome stability.Ciliates provide excellent model organisms with which to gain better understandinginto the regulation of genome stability in eukaryotes. In the ciliate Parameciumtetraurelia, differentiation of the somatic genome from the germline genome ischaracterized by massive and reproducible programmed DNA elimination events. Longregions of several kilobases in length, containing repeated sequences and transposableelements are imprecisely eliminated, whereas 45,000 short, dispersed, single-copyInternal Eliminated Sequences (IESs) are precisely excised at the nucleotide level. Aspecific class of small RNAs, called scnRNAs, is involved in the epigenetic regulation ofDNA deletion. How scnRNAs may guide DNA elimination in Paramecium remains tobe discovered. Here, we investigated whether chromatin structure, in particular histonepost-translational modifications known to be associated with repressive chromatin,might control DNA elimination. We showed that trimethylated lysine 9 and 27 onhistone H3 (H3K9me3 and H3K27me3) appear in the developing somaticmacronucleus when DNA elimination occurs. We identified the Polycomb-groupprotein, Ezl1, and showed that it is a dual histone methyltransferase that catalyzes bothH3K9me3 and H3K27me3 in vitro and in vivo. Genome-wide analyses show thatscnRNA-mediated H3K9me3 and H3K27me3 deposition is necessary for theelimination of long, repeated germline DNA. Conversely, single copy IESs displaydifferential sensitivity to depletion of scnRNAs and Ezl1, unveiling the existence ofpartially overlapping pathways in programmed DNA elimination. Our study revealsthat cis-acting determinants, such as DNA length, also contribute to the definition ofgermline sequences to delete. We further showed that Ezl1 is required fortranscriptional repression of transposable elements. We suggest that H3K9me3 andH3K27me3 pathways cooperate and contribute to safeguard the Paramecium somaticgenome against intragenomic parasites.
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Related Subjects:(14)
- Épigénétique.
- Réarrangement génétique.
- Transposons.
- Petits ARN.
- Méthyltransférases.
- Paramecium tetraurella -- Dissertation universitaire.
- ARN non traduit -- Dissertation universitaire.
- Histone -- Dissertation universitaire.
- Protéines de répression -- Dissertation universitaire.
- Génome -- Dissertation universitaire.
- Histone méthyltransferase
- ARN non codants
- Réarrangements du génome
- Répression transcriptionelle