The role of MET1 in RNA-directed de novo and maintenance methylation of CG dinucleotides

Werner Aufsatz, Michael Mette, Antonius J.M. Matzke, Marjori Matzke*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

85 Scopus citations

Abstract

A genetic screen for mutants defective in RNA-directed DNA methylation and transcriptional silencing of the constitutive nopaline synthase (NOS) promoter in Arabidopsis identified two independent mutations in the gene encoding the DNA methyltransferase MET1. Both mutant alleles are disrupted structurally in the MET1 catalytic domain, suggesting that they are complete loss of function alleles. Experiments designed to test the effect of a met1 mutation on both RNA-directed de novo and maintenance methylation of the target NOS promoter revealed in each case approximately wild type levels of non-CG methylation together with significant reductions of CG methylation. These results confirm a requirement for MET1 to maintain CG methylation induced by RNA. In addition, the failure to establish full CG methylation in met1 mutants, despite normal RNA-directed de novo methylation of Cs in other sequence contexts, indicates that MET1 is required for full de novo methylation of CG dinucleotides. We discuss MET1 as a site-specific DNA methyltransferase that is able to maintain CG methylation during DNA replication and contribute to CG de novo methylation in response to RNA signals.

Original languageEnglish (US)
Pages (from-to)793-804
Number of pages12
JournalPlant Molecular Biology
Volume54
Issue number6
DOIs
StatePublished - Apr 1 2004

Keywords

  • Cytosine methylation
  • DNA methyltransferase
  • MET1
  • Nopaline synthase promoter
  • RNA-directed DNA methylation
  • Transcriptional gene silencing

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Genetics
  • Plant Science

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