siRNAs compete with miRNAs for methylation by HEN1 in Arabidopsis

Nucleic Acids Res. 2010 Sep;38(17):5844-50. doi: 10.1093/nar/gkq348. Epub 2010 May 6.

Abstract

Plant microRNAs (miRNAs) and small interfering RNAs (siRNAs) bear a 2'-O-methyl group on the 3'-terminal nucleotide. This methyl group is post-synthetically added by the methyltransferase protein HEN1 and protects small RNAs from enzymatic activities that target the 3'-OH. A mutagenesis screen for suppressors of the partial loss-of-function hen1-2 allele in Arabidopsis identified second-site mutations that restore miRNA methylation. These mutations affect two subunits of the DNA-dependent RNA polymerase IV (Pol IV), which is essential for the biogenesis of 24 nt endogenous siRNAs. A mutation in RNA-dependent RNA polymerase 2, another essential gene for the biogenesis of endogenous 24-nt siRNAs, also rescued the defects in miRNA methylation of hen1-2, revealing a previously unsuspected, negative influence of siRNAs on HEN1-mediated miRNA methylation. In addition, our findings imply the existence of a negative modifier of HEN1 activity in the Columbia genetic background.

Publication types

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

MeSH terms

  • Alleles
  • Amino Acid Sequence
  • Arabidopsis / enzymology
  • Arabidopsis / genetics*
  • Arabidopsis Proteins / genetics*
  • Arabidopsis Proteins / metabolism
  • DNA-Directed RNA Polymerases / genetics*
  • Fertility
  • Methylation
  • Methyltransferases / genetics
  • Methyltransferases / metabolism
  • MicroRNAs / metabolism*
  • Molecular Sequence Data
  • Mutation
  • RNA, Small Interfering / metabolism*
  • RNA-Dependent RNA Polymerase / genetics
  • Suppression, Genetic

Substances

  • Arabidopsis Proteins
  • HEN1 protein, Arabidopsis
  • MicroRNAs
  • RNA, Small Interfering
  • Methyltransferases
  • RNA polymerase IV, Arabidopsis
  • RNA polymerase V, Arabidopsis
  • RDR2 protein, Arabidopsis
  • RNA-Dependent RNA Polymerase
  • DNA-Directed RNA Polymerases