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Contenuto archiviato il 2022-12-23

Dissection of RNA interference phenomenon, a defence system in eukaryotes

Obiettivo

Eukaryotes silence gene expression in the presence of homologous double stranded RNA (dsRNA). The short RNA fragments of dsRNA select mRNA for degradation and /or silence transcription of a homologous gene. This phenomenon of RNA interference (RNAi) is considered to be defence system directed against viruses, supernumerary copies of genes and transposable elements in eukaryotic genome. This conservative silencing mechanism is proposed to be especially effective in the germline.

Two different genomic classes of repeats in Drosophila melanogaster suppressed by RNAi mediated silencing will be compared as the targets of RNAi:
1. The tandemly repeated Stellate genes the upregulation of which leads to male sterility; their suppression is mediated by a naturally evolved system of silencing;
2. A wide spectrum of transposable elements, which may be targets of host defense systems controlling their expression and transposition. Previous results have revealed that silencing of tandemly repeated Stellates and three different transposable elements (mdg1, 1731 and F) is controlled by non-identical, but overlapping sets of genes.

The function of several conservative genes believed to be involved in RNAi (aubergine, homeless and piwi) will be related to particular steps of the RNAi mechanism:
1. The sense and antisense RNAs as well as a quantity of total and polyadenylated cytoplasmic RNAs of Stellate tandems and dispersed transposable elements will be estimated. The possibility of transcriptional silencing at the level of chromatin will be investigated for both classes of the repeats;
2. Mutations will be used to investigate the genetic control of the production of small RNAs or the downstream events of silencing and the involvement of particular genes in the generation of small RNAs or other steps will be determined.

RNAi mediated control of genetic systems which when disrupted result in female (I-R system controlling I-element transposition) or male (Stellate genes) sterility will be investigated to look for sex specific differences. These studies will encompass a wide spectrum of transposable elements using different mechanisms of transpositions and modes of expression (LTR and non-LTR retrotransposons). The results obtained will identify genes involved in RNAi mediated control of their expression and transposition. Since the molecular mechanisms of RNAi appear to be conserved between plants and animals results from this study should be relevant to mammalian systems and in particular to the stability of the human genome

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Coordinatore

Centre National de la Recherche Scientifique
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Indirizzo
rue de la Cardonille
34396 Montpellier
Francia

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