Soutenance HDR Julien Bischerour

Title: Mechanisms of Programmed DNA Elimination in Paramecium

Abstract:
In the ciliate Paramecium tetraurelia, massive genome rearrangements occur during the formation of a new somatic nucleus at each sexual cycle. These rearrangements lead to the elimination of approximately 30% of the germline genome. DNA double-strand breaks are introduced by a specific endonuclease derived from the domestication of a PiggyBac family transposase and are subsequently repaired through the classical non-homologous end joining (cNHEJ) pathway. The boundaries of the eliminated genomic regions lack specific sequences that could serve as recognition motifs for the excision machinery. Under these conditions, how are such precise DNA breaks introduced?
My work aims to characterize the components of the excision machinery and the mechanisms that allow targeting of the sequences to be eliminated. It also seeks to understand how DNA breaks are repaired in such a precise and robust manner across the thousands of eliminated sequences.

Members of the jury:
• Pascale Lesage, DR (CNRS), Institut de Recherche Saint-Louis, Paris (Reviewer)
• Vincent Parissi, DR (CNRS), Université Bordeaux 2, Bordeaux (Reviewer)
• Jean-Pierre de Villartay, DR (INSERM), Institut Imagine, Paris (Reviewer)
• Aurélie Hua-Van, Professor, Université Paris-Saclay, EGCE, Gif-sur-Yvette (Examiner)
• Josée Guirouilh-Barbat, DR (CNRS), Institut Curie, Paris (Examiner)
• Éric Meyer, DR (CNRS), IBENS, Paris (Examiner)