The C-terminal domain of Arabidopsis ROS1 DNA demethylase interacts with histone H3 and is required for DNA binding and catalytic activity

Abstract

Active DNA demethylation plays an important role in controlling methylation patterns in eukaryotes. In plants, the DEMETER-LIKE (DML) family of 5-methylcytosine DNA glycosylases initiates DNA demethylation through a base excision repair pathway. However, it is poorly understood how these DNA demethylases are recruited to their target loci and the role that histone marks play in this process. Arabidopsis REPRESSOR OF SILENCING 1 (ROS1) is a representative enzyme of the DML family, whose members are uniquely characterized by a basic amino-terminal domain mediating nonspecific binding to DNA, a discontinuous catalytic domain, and a conserved carboxy-terminal domain of unknown function. Here, we show that ROS1 interacts with the N-terminal tail of H3 through its C-terminal domain. Importantly, phosphorylation at H3 Ser28, but not Ser10, abrogates ROS1 interaction with H3. Conserved residues at the C-terminal domain are not only required for H3 interaction, but also for efficient DNA binding and catalytic activity. Our findings suggest that the C-terminal domain of ROS1 may function as a histone reader module involved in recruitment of the DNA demethylase activity to specific genomic regions.