Role of the DRM and CMT3 Methyltransferases in RNA-Directed DNA Methylation

Xiaofeng Cao, Werner Aufsatz, Daniel Zilberman, Michael Mette, Michael S. Huang, Marjori Matzke, Steven E. Jacobsen*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

379 Scopus citations

Abstract

RNA interference is a conserved process in which double-stranded RNA is processed into 21-25 nucleotide siRNAs that trigger posttranscriptional gene silencing. In addition, plants display a phenomenon termed RNA-directed DNA methylation (RdDM) in which DNA with sequence identity to silenced RNA is de novo methylated at its cytosine residues. This methylation is not only at canonical CpG sites but also at cytosines in CpNpG and asymmetric sequence contexts. In this report, we study the role of the DRM and CMT3 DNA methyltransferase genes in the initiation and maintenance of RdDM. Neither drm nor cmt3 mutants affected the maintenance of preestablished RNA-directed CpG methylation. However, drm mutants showed a nearly complete loss of asymmetric methylation and a partial loss of CpNpG methylation. The remaining asymmetric and CpNpG methylation was dependent on the activity of CMT3, showing that DRM and CMT3 act redundantly to maintain non-CpG methylation. These DNA methyltransferases appear to act downstream of siRNAs, since drm1 drm2 cmt3 triple mutants show a lack of non-CpG methylation but elevated levels of siRNAs. Finally, we demonstrate that DRM activity is required for the initial establishment of RdDM in all sequence contexts including CpG, CpNpG, and asymmetric sites.

Original languageEnglish (US)
Pages (from-to)2212-2217
Number of pages6
JournalCurrent Biology
Volume13
Issue number24
DOIs
StatePublished - Dec 16 2003

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)

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