Programmed genome rearrangements
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Institut de Biologie Intégrative de la Cellule (I2BC), UMR 9198, Université Paris-Saclay
1 avenue de la Terrasse
91198 Gif-sur-Yvette cedex
France
Scientific Interest
DNA transposons move around their host genomes thanks to the action of their transposase, an enzyme that binds specifically to transposon ends and cleaves DNA to initiate transposition. We use the ciliate Paramecium tetraurelia as a unicellular model to study how transposable elements (TE) contribute to genome dynamics. Paramecium harbors two distinct types of nuclei in its cytoplasm: the somatic macronucleus (MAC), in which gene transcription takes place, and two germline micronuclei (MIC), essential for sexual reproduction. At each sexual cycle, a new MAC differentiates from the MIC, a process that includes the elimination of ~30% of germline DNA, including TEs and other DNA repeats. An essential actor in programmed somatic genome rearrangements is the PiggyMac endonuclease, a catalytically active domesticated PiggyBac transposase, which, in association with five distinct domesticated transposases from the same family, cleaves both DNA strands at the ends of ~45,000 Tc/mariner-related germline sequences and initiates their precise excision. A major research line of our team aims at understanding the molecular mechanisms involved in programmed DNA elimination and the epigenetic control of genome rearrangements. We use genetic, biochemical and cellular approaches combined with high-throughput next-generation sequencing to characterize the endonuclease-associated complex, the function of its different subunits and the way it recognizes its chromatin targets. We also study how the endonuclease complex interacts with the non-homologous end joining (NHEJ) repair pathway and ensures that programmed rearrangements do not jeopardize genome integrity. Within the frame of a large-scale France Génomique collaborative sequencing project coordinated by Sandra Duharcourt, also a member of the GDR, our team contributes to the assembly and annotation of the germline and somatic genomes of 13 Paramecium species.
DNA transposons move around their host genomes thanks to the action of their transposase, an enzyme that binds specifically to transposon ends and cleaves DNA to initiate transposition. We use the ciliate Paramecium tetraurelia as a unicellular model to study how transposable elements (TE) contribute to genome dynamics. Paramecium harbors two distinct types of nuclei in its cytoplasm: the somatic macronucleus (MAC), in which gene transcription takes place, and two germline micronuclei (MIC), essential for sexual reproduction. At each sexual cycle, a new MAC differentiates from the MIC, a process that includes the elimination of ~30% of germline DNA, including TEs and other DNA repeats. An essential actor in programmed somatic genome rearrangements is the PiggyMac endonuclease, a catalytically active domesticated PiggyBac transposase, which, in association with five distinct domesticated transposases from the same family, cleaves both DNA strands at the ends of ~45,000 Tc/mariner-related germline sequences and initiates their precise excision. A major research line of our team aims at understanding the molecular mechanisms involved in programmed DNA elimination and the epigenetic control of genome rearrangements. We use genetic, biochemical and cellular approaches combined with high-throughput next-generation sequencing to characterize the endonuclease-associated complex, the function of its different subunits and the way it recognizes its chromatin targets. We also study how the endonuclease complex interacts with the non-homologous end joining (NHEJ) repair pathway and ensures that programmed rearrangements do not jeopardize genome integrity. Within the frame of a large-scale France Génomique collaborative sequencing project coordinated by Sandra Duharcourt, also a member of the GDR, our team contributes to the assembly and annotation of the germline and somatic genomes of 13 Paramecium species.
Thematic