17 - scientific report scientificreport A SNF2-like protein...

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A SNF2-like protein facilitates dynamic control of DNA methylation Tatsuo Kanno 1 *, Werner Aufsatz 1 *, Estelle Jaligot 1 ,MichaelFlorianMette 2 ,MarjoriMatzke 1+ &Anton iusJ .M .Matzke 1 1 Gregor Mendel Institute of Molecular Plant Biology, Austrian Academy of Sciences, UZA2, Pharmazie Zentrum, Vienna, Austria, and 2 IPK Gatersleben, Gatersleben, Germany DRD1 is a SNF2-like protein previously identified in a screen for mutants defective in RNA-directed DNA methylation of a seed promoter in Arabidopsis . Although the initial study established a role for DRD1 in RNA-directed DNA methylation, it did not address whether DRD1 is needed for de novo or maintenance methylation, or whether it is required for methylation of other target sequences. We show here that DRD1 is essential for RNA- directed de novo methylation and acts on different target promoters. In addition, an unanticipated role for DRD1 in erasure of CG methylation was shown when investigating maintenance methylation after segregating away the silencing trigger. DRD1 is unique among known SNF2-like proteins in facilitating not only de novo methylation of target sequences in response to RNA signals, but also loss of methylation when the silencing inducer is withdrawn. The opposing roles of DRD1 could contribute to the dynamic regulation of DNA methylation. Keywords: demethylation; de novo methylation; maintenance methylation; RNA-directed DNA methylation; SNF2-like protein EMBO reports advance online publication 10 June 2005; doi:10.1038/sj.embor.7400446 INTRODUCTION RNA-directed DNA methylation has been documented in plants (Mathieu & Bender, 2004) and in human cells (Kawasaki & Taira, 2004; Morris et al , 2004). Genetic analyses in Arabidopsis have identified the DNA methyltransferases that catalyse de novo cytosine (C) methylation in response to RNA signals (Cao et al , 2003; Aufsatz et al , 2004) and maintain symmetrical C(N)G methylation (N is A, T or C) in cooperation with histone-modifying enzymes (Jones et al , 2001; Aufsatz et al , 2002a; Jackson et al , 2002; Malagnac et al , 2002). A plant-specific SNF2-like putative chromatin-remodelling protein, DRD1, was identified in a screen for mutants impaired in RNA-directed DNA methylation and silencing of the seed-specific a 0 promoter (Kanno et al , 2004). From the initial genetic screen, it was unclear whether drd1 mutants are deficient in de novo methylation or in maintenance methylation. In the case of RNA-directed DNA methylation, de novo methylation leads to the modification of Cs in all sequence contexts within the region of RNA–DNA sequence identity, whereas maintenance methylation refers to perpetuation of symmetrical C(N)G methylation during DNA replication in the absence of the RNA trigger (Matzke et al , 2004). To further understand the role of DRD1 in RNA-directed DNA methylation, we examined separately the effects of a drd1 mutation on RNA-directed de novo methylation and on maintenance methylation. We report here that DRD1 influences both of these processes in a manner that facilitates the dynamic regulation of DNA methylation.
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17 - scientific report scientificreport A SNF2-like protein...

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