Nuclear RNAi

In plants, RNA-directed DNA methylation (RdDM) represents the most important mechanism for the establishment of de novo methylation patterns. Similar to induction of transcriptional gene silencing (TGS) and heterochromatin formation in Schizosaccharomyces pombe (fission yeast), RdDM is induced by double-stranded RNA (dsRNA) (Fig. 1). In mammals, de novo DNA methylation appears to also correlate with the presence of non-coding RNAs. Thus, it is reasonable to assume that RdDM exists in mammals and that it is involved in epigenetic processes, including TGS. In order to find further support for this hypothesis, we are using plants as a model system to examine RdDM. It should be noted that even in plants where RdDM was detected in 1994 it is still barely characterized. The information gained from plants will be used to investigate whether in mammals, analogous components are expressed and whether they are associated with de novo DNA methylation.

Model of RNA-mediated initiation of DNA methylation and heterochromatin formation in plants (“nuclear RNAi”).

See also: Wassenegger M. (2005). The role of the RNAi machinery in heterochromatin formation. Cell 122: 13-16.

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