|Drosophila genetics and epigenetics - CNRS URA 2578|
|HEAD||Dr Christophe ANTONIEWSKI / email@example.com|
|MEMBERS||Mathieu Bartoletti / Bassam Berry / Dr Corinne Besnard-Guerrin / Dr Anne-Laure Bougé / Dr Delphine Fagegaltier / Caroline Jacquier / Josette Pidoux / Edwige Seguy / Dr Hélène Thomassin
Three classes of non-coding small RNAs mediate gene silencing in Drosophila. 21-nt siRNAs are produced from long double-stranded RNAs by Dicer-2 and trigger RNAi. The RNAi pathway provides the main defense against RNA viruses in plant and insects. ~23-nt miRNAs are processed from genome-encoded stem-loop precursors by Dicer-1 and repress mRNAs. Over the past few years, miRNAs have emerged as important regulators of development, cell proliferation and cell homeostasis. ~25-nt piRNAs derive from pericentromeric transposons transcripts through a “Ping-Pong” mechanism mediated by the Piwi, Aubergin and Argonaute-3 Argonautes. The piRNA pathway silences transposons in the germ line and has been involved in heterochromatin formation.
Deciphering the role of small RNAs in the regulation of Drosophila genome.
Our projects are aimed at understanding the role of small RNAs in the regulation of gene expression and chromosome structure in Drosophila.
We established a reporter system based on GFP silencing by artificial miRNAs. Using this reporter system, we performed wide-genome RNAi screen in cultured cells and identified genes potentially involved in the biogenesis and/or the activity of miRNAs. We are currently characterizing these candidates.
We have built, in collaboration with Pasteur-Génopole®, LNA oligonucleotide microarrays to perform genome wide analyses of miRNA expression profiles during development. Using this approach, we identified miRNAs induced at the onset of metamorphosis and potentially involved in the hormonally regulated genetic cascade that orchestrates Drosophila development during this period. We are also involved in collaborations to characterize miRNAs involved in immune responses to pathogens, aging and neurodegenerative diseases.
Another experimental approach consists in perturbing small RNA pathways by expressing proteins that sequester siRNAs and block their silencing activity. We have tested a battery of such inhibitors naturally encoded by a variety of plant viruses to counteract antiviral RNAi host responses and shown that they also function as potent RNAi inhibitors in Drosophila. Indeed, these RNAi suppressors dramatically increase susceptibility to viral infections, demonstrating that RNAi is a genuine antiviral response in this organism. We have recently shown that RNAi suppressors perturb in addition heterochromatin structure in somatic tissues, by sequestering endogenous siRNAs derived from transposons transcripts. This demonstrate that with regard to the control of chromatin dynamics, siRNAs play in somatic tissues a role similar to the one of piRNAs in the germ line.
Most recently, we developed in collaboration with Pasteur-Génopole (PF2) deep sequencing approaches to characterize the repertoires of antiviral siRNAs that accumulate in fly cells during various viral infections. This prompted us to test the hypothesis that overlapping but distinct siRNA pathways may be activated by the host, depending on the type of virus involved.
Keywords: RNAi, Chromatin structure, Epigenetics, miRNA, siRNA, Drosophila, metamorphosis, Ecdysone, antiviral immune response
1. van Rij, R.P., Saleh, M.C., Berry, B., Foo, C., Houk, A., Antoniewski, C., and Andino, R. (2006). The RNA silencing endonuclease Argonaute 2 mediates specific antiviral immunity in Drosophila melanogaster. Genes Dev 20, 2985-2995.
2. Jaubert, S., Mereau, A., Antoniewski, C., and Tagu, D. (2007). MicroRNAs in Drosophila: the magic wand to enter the Chamber of Secrets? Biochimie 89, 1211-1220.
3. Carre, C., Ciurciu, A., Komonyi, O., Jacquier, C., Fagegaltier, D., Pidoux, J., Tricoire, H., Tora, L., Boros, I.M., and Antoniewski, C. (2008). The Drosophila NURF remodelling and the ATAC histone acetylase complexes functionally interact and are required for global chromosome organization. EMBO Rep 9, 187-192.
4. Deddouche S, Matt N, Budd A, Mueller S, Kemp C, Galiana-Arnoux D, Dostert C, Antoniewski C, Hoffmann JA, and Imler JL. (2008). The DExD/H-box helicase Dicer-2 mediates the induction of antiviral activity in drosophila. Nature Immunol 9, 1425-32.
5. Saleh MC, Tassetto M, van Rij RP, Goic B, Gausson V, Berry B, Jacquier C, Antoniewski C and Andino R (2008) Antiviral immunity in Drosophila requires systemic RNA interference spread
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Activity Reports 2009 - Institut Pasteur
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