ROS3 is an RNA-binding protein required for DNA demethylation in Arabidopsis.

DNA methylation is an important epigenetic mark for transcriptional gene silencing (TGS) in diverse organisms. Recent studies suggest that the methylation status of a number of genes is dynamically regulated by methylation and demethylation. In Arabidopsis, active DNA demethylation is mediated by the (repressor of silencing 1) subfamily of 5-methylcytosine DNA glycosylases through a base excision repair pathway. These demethylases have critical roles in erasing DNA methylation and preventing TGS of target genes. However, it is not known how the demethylases are targeted to specific sequences. Here we report the identification of an essential regulator of DNA demethylation that contains an RNA recognition motif. Analysis of ros3 mutants and ros1 ros3 double mutants suggests that acts in the same genetic pathway as duanyu16701 to prevent DNA hypermethylation and TGS. Gel mobility shift assays and analysis of duanyu16703 immunoprecipitate from plant extracts shows that duanyu16703 binds to small RNAs in vitro and in vivo. Immunostaining shows that duanyu16703 and duanyu16701 proteins co-localize in discrete foci dispersed throughout the nucleus. These results demonstrate a critical role for duanyu16703 in preventing DNA hypermethylation and suggest that DNA demethylation by duanyu16701 may be guided by RNAs bound to

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