RNA interference and mammalian chromatin modification

RNA interference (RNAi) is a post-transcriptional process through which double-stranded RNA (dsRNA) triggers sequence specific degradation of RNA targets thus silencing a gene or family of genes. Recently, RNAi has also been shown to play a role at the transcriptional level through the modification of higher-order chromatin structure. In fission yeast and Drosophila, loss-of-function analyses reveal that components of the RNAi pathway are required for heterochromatin formation. It has been shown that RNAi machinery is required for the production of small interfering RNAs (siRNAs) which are homologous to specific chromosomal loci. These siRNAs are incorporated into an RNA-induced initiation of transcriptional gene silencing (RITS) complex and direct it to the homologous chromosomal region. This complex is then thought to recruit chromatin modification enzymes resulting in the establishment of transcriptionally silent heterochromatin. It is the aim of this fellowship to determine if components of the RNAi pathway play a similar role in mammalian heterochromatin formation. Using a protein tethering approach, epitope tagged RNAi components will be anchored at specific chromosomal loci in the vicinity of reporter genes and the effect on the reporter gene and chromatin neighbourhood analysed. This approach will also enable RNAi/Chromatin silencing complexes to be isolated and characterised.