Let’s face it: it’s an RNA world. In addition to RNA’s many genetic, catalytic, and structural roles, the discovery of small non-coding RNAs has unveiled an entire continent of epigenetic functions. Small RNAs act in processes such as mRNA destruction, translational inhibition, and DNA methylation. Now it appears that, at least in plants, small RNAs are also involved in DNA demethylation.
In a recent Nature paper, Jian-Kang Zhu and colleagues at the University of California Riverside, Washington University, the University of Maryland, and Shanghai Jiao Tong University showed that ROS3, a protein required for DNA demethylation in Arabidopsis, binds small RNAs.
By conducting a genetic screen for demethylating proteins in Arabidopsis, Zhu and co-workers identified ROS3, a regulator of DNA demethylation that functions in the same pathway as the known DNA demethylase ROS1. Interestingly, ROS3 has an RNA recognition motif that binds to short single-stranded RNAs in vitro and in vivo.
Small RNAs that immunoprecipitated with ROS3 corresponded to genomic regions that were more heavily methylated in ros3 mutants, which provides the first evidence that ROS3-associated small RNAs can direct demethylation of target sequences by ROS1. Get all the details in Nature, October 2008