Résumé : Small RNAs are used to silence transposable elements (TEs) in many eukaryotes, which use surprisingly diverse evolutionary solutions to identify TEs. We have previously reported that in the ciliated protozoan Tetrahymena thermophile, small RNA-mediated comparison of the germline and somatic genomes underlies identification of TE-related sequences, which are then eliminated from the soma. In addition, we recently found an additional layer of small RNA-mediated identification of TE-related sequences in Tetrahymena. We found that a limited set of Internal Eliminated Sequences (IESs) containing potentially active TEs produces a class of small RNAs that recognize not only the IESs from which they are derived but also other IESs in trans. This trans-recognition triggers the expression of yet another novel class of small RNAs that identify other IESs. Therefore, TE-related sequences in Tetrahymena are robustly targeted for elimination by a genome-wide trans-recognition network accompanied by a chain reaction of small RNA production. In this presentation, I will discuss our latest picture of small RNA-directed DNA elimination with two “trans” mechanisms : small RNA-mediated trans-generational genome comparison and trans-recognition network.
Lieu : Auditorium - Bâtiment 21, campus de gif