Project : Dissection of the dual role of piRNAs in Drosophila

Repression of the transposable elements (TE) expression is crucial to ensure maintenance of genome integrity. In animals, TE repression necessitates the action of a specific class of small non-coding RNA called piRNAs (PIWI-interacting RNA). Piwi-loaded piRNAs target TE nascent transcript in the nucleus and subsequently promote acquisition of several histone modifications marks among which H3K9me3 is particularly crucial to initiate TE transcriptional repression. Interestingly, however, it appears that nuclear piRNAs/Piwi complexes are also able to target piRNA source loci called piRNAs clusters. In these loci, their presence together with Piwi is important to promote transcriptional maintenance and subsequent production of piRNAs from dual-stranded transcripts. How piRNA/Piwi and their co-factors may have such opposite effects on transcription remains unclear. This project aims to resolve this transcriptional dual role of piRNAs. Using genetics, biochemical and high-resolutive microscopy approaches, we expect to decipher this paradoxical transcriptional behavior of piRNAs biology.