<i>ARGONAUTE4</i> Control of Locus-Specific siRNA Accumulation and DNA and Histone Methylation

TLDR

Proteins of the ARGONAUTE family are important in diverse posttranscriptional RNA‑mediated gene‑silencing systems as well as in transcriptional gene silencing in Drosophila and fission yeast and in programmed DNA elimination in Tetrahymena. We cloned ARGONAUTE4 (AGO4) from a screen for mutants that suppress silencing of the Arabidopsis SUPERMAN (SUP) gene. The ago4‑1 mutant reactivated silent SUP alleles, reduced CpNpG and asymmetric DNA methylation and H3K9 methylation, blocked accumulation of 25‑nt siRNAs from the retroelement AtSN1, and these results indicate that AGO4 and long siRNAs direct chromatin modifications such as histone methylation and non‑CpG DNA methylation.

Abstract

Proteins of the ARGONAUTE family are important in diverse posttranscriptional RNA-mediated gene-silencing systems as well as in transcriptional gene silencing in Drosophila and fission yeast and in programmed DNA elimination in Tetrahymena . We cloned ARGONAUTE4 ( AGO4 ) from a screen for mutants that suppress silencing of the Arabidopsis SUPERMAN ( SUP ) gene. The ago4-1 mutant reactivated silent SUP alleles and decreased CpNpG and asymmetric DNA methylation as well as histone H3 lysine-9 methylation. In addition, ago4-1 blocked histone and DNA methylation and the accumulation of 25-nucleotide small interfering RNAs (siRNAs) that correspond to the retroelement AtSN1 . These results suggest that AGO4 and long siRNAs direct chromatin modifications, including histone methylation and non-CpG DNA methylation.