Molecular Mechanism of Action of Plant DRM De Novo DNA Methyltransferases

Cell. 2014 May 22;157(5):1050-60. doi: 10.1016/j.cell.2014.03.056.

Abstract

DNA methylation is a conserved epigenetic gene-regulation mechanism. DOMAINS REARRANGED METHYLTRANSFERASE (DRM) is a key de novo methyltransferase in plants, but how DRM acts mechanistically is poorly understood. Here, we report the crystal structure of the methyltransferase domain of tobacco DRM (NtDRM) and reveal a molecular basis for its rearranged structure. NtDRM forms a functional homodimer critical for catalytic activity. We also show that Arabidopsis DRM2 exists in complex with the small interfering RNA (siRNA) effector ARGONAUTE4 (AGO4) and preferentially methylates one DNA strand, likely the strand acting as the template for RNA polymerase V-mediated noncoding RNA transcripts. This strand-biased DNA methylation is also positively correlated with strand-biased siRNA accumulation. These data suggest a model in which DRM2 is guided to target loci by AGO4-siRNA and involves base-pairing of associated siRNAs with nascent RNA transcripts.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Arabidopsis / enzymology*
  • Arabidopsis / metabolism
  • Arabidopsis Proteins / metabolism
  • Argonaute Proteins / metabolism
  • Catalytic Domain
  • Methyltransferases / chemistry
  • Methyltransferases / metabolism*
  • Models, Molecular
  • Molecular Sequence Data
  • Tobacco / enzymology*
  • Tobacco / metabolism

Substances

  • AGO4 protein, Arabidopsis
  • Arabidopsis Proteins
  • Argonaute Proteins
  • Methyltransferases
  • DRM1 protein, Arabidopsis
  • DRM2 protein, Arabidopsis