Chromatin remodeling may open up DNA to RNA-mediated silencing

In a finding that deepens our understanding of epigenetic regulation, researchers at the Gregor Mendel Institute of Molecular Plant Biology in Vienna have identified a novel protein in Arabidopsis that may help so-called short guide RNAs and silencing effector proteins target specific DNA sequences for modification.

The 'nuclear side' of RNA interference (RNAi) is increasingly recognized as an important part of RNA-mediated gene silencing pathways. Short RNAs and proteins of the RNAi machinery can direct epigenetic modifications, such as DNA cytosine methylation and histone methylation, to homologous regions of the genome in various organisms. Still unclear is whether short RNAs interact directly with target DNA sequences by base pairing and if so, how they gain access to target DNA that is packaged into nucleosomes in chromatin.

In a genetic a screen for mutants defective in RNA-directed DNA methylation in Arabidopsis thaliana, Dr. Tatsuo Kanno and colleagues identified DRD1, a previously undefined SNF2 chromatin remodeling protein in plants. The involvement of DRD1 in RNA-directed DNA methylation suggests that chromatin remodeling is required to render nucleosomal DNA accessible to RNA signals and/or DNA methyltransferases. DRD1 is the first chromatin remodeling factor implicated in an RNA-guided epigenetic modification of the genome.

Tatsuo Kanno, M. Florian Mette, David P. Kreil, Werner Aufsatz, Marjori Matzke, and Antonius J.M. Matzke: "Involvement of Putative SNF2 Chromatin Remodeling Protein DRD1 in RNA-Directed DNA Methylation"

Publishing in Current Biology, Volume 14, Number 9, May 4, 2004.

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