Double stranded RNA (dsRNA) is potent inducer of gene silencing. The mechanism by which these molecules
induce silencing is evolutionary conserved, and represents a very powerful and specific way of gene activity
control. One of the intermediates of this silencing process is a short RNA(sRNA) molecule that has been named
short interfering RNA (siRNA) or micro RNA (miRNA). These molecules act as guides for either an RNA
degradation enzyme that is active in the cytosol or a complex that targets translation inhibition. In addition to these
cytosolic events, nuclear effects of dsRNA have also been observed. In plants, dsRNA leads to methylation of
homologous DNA sequences, and induces transcriptional silencing when promoter DNA is targeted. In yeast,
dsRNA mediated processes have been implicated in centromere function. In animals, evidence for such nuclear
effects has been obtained as well. For example, phenotypes of C. elegans mutants defective in RNAi suggest an
impaired centromere function, and partially overlap with phenotypes associated with defects in the maintenance of
silent chromatin states.
In this research proposal we aim at a better understanding of the nuclear effects of dsRNA. We will do this by
analyzing nuclear dsRNA processing, by identifying nuclear sRNA, by analyzing proteins associating with the
nuclear sRNA and by analyzing the effects of nuclear sRNA on chromatin modifications and transcriptional
activity.