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ADN ribosomique 5S chez Arabidopsis thaliana : dynamique chromatinienne et ARN polymérase IV

Abstract : In Arabidopsis thaliana, 5S rRNA genes are found clustered at pericentromeric heterochromatin of chromosomes 3, 4 and 5. 5S rRNA genes transcription is epigenetically regulated through the formation of specific chromatin structure. In order to determine the events that lead to the establishment of such structures, a study during the first steps of post-germinative plant development was done. Unexpectedly, we observed a decondensation followed by a rapid "re"condensation of 5S rDNA chromatin. These two phenomenons are respectively dependent on ROS1 and RNA polymerase IV activities. A more precise analyse on the two Pol IV isoforms, i.e. Pol IVa and Pol IVb, revealed a new function for Pol IVb. Indeed, in addition to its activity in a partnership with Pol IVa, Pol IVb has a specific role in the silencing and the compaction of the 5S rDNA locus from the chromosome 4. This activity seems to be independent of the Pol IVa activity and the RNA dependent DNA methylation pathway.
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Julien Douet. ADN ribosomique 5S chez Arabidopsis thaliana : dynamique chromatinienne et ARN polymérase IV. Génétique. Université Blaise Pascal - Clermont-Ferrand II; Université d'Auvergne - Clermont-Ferrand I, 2008. Français. ⟨tel-00731526⟩

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