The Arabidopsis Nucleosome Remodeler DDM1 Allows DNA Methyltransferases to Access H1-Containing Heterochromatin

Nucleosome remodelers of the DDM1/Lsh family are required for DNA methylation of transposable elements, but the reason for this is unknown. How DDM1 interacts with other methylation pathways, such as small-RNA-directed DNA methylation (RdDM), which is thought to mediate plant asymmetric methylation through DRM enzymes, is also unclear. Here, we show that most asymmetric methylation is facilitated by DDM1 and mediated by the methyltransferase CMT2 separately from RdDM. We find that heterochromatic sequences preferentially require DDM1 for DNA methylation and that this preference depends on linker histone H1. RdDM is instead inhibited by heterochromatin and absolutely requires the nucleosome remodeler DRD1. Together, DDM1 and RdDM mediate nearly all transposon methylation and collaborate to repress transposition and regulate the methylation and expression of genes. Our results indicate that DDM1 provides DNA methyltransferases access to H1-containing heterochromatin to allow stable silencing of transposable elements in cooperation with the RdDM pathway.

#RNA Biology: Point-of-View

@rnomics/RNA landesbioscience.com

200) && (this.width >= this.height) ? 200: true); max-height: 200px; height: expression((this.height > 200) && (this.height >= this.width) ? 200: true); border: none;’/> Long non-coding #RNAs (l#ncRNAs) can be important regulators of various biological processes such as #RNA-directed DNA methylation (RdDM). In the RdDM pathway, recruitment of the DNA methylation complex is mediated through complementary pairing between scaffold #RNAs and Argonaute-associated #siRNAs. Scaffold #RNAs are chromatin-associated l#ncRNAs transcribed by #RNA polymerase Pol V or Pol II, while #siRNAs originate from Pol IV- or Pol II-dependent production of l#ncRNAs. In contrast to the vast liter… posted by friends:  (1)

@RNABiology: Regulation of long non-coding #RNAs in the #RNA-directed DNA methylation pathway landesbioscience.com/journals/rnabi… 21.08.2014 20.04.09

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