Histone arginine demethylation by RDMe1

Histone methylation mainly occurs on lysine and arginine residues. While lysine methylation can be removed by LSD1 and JmjC domain-containing demethylases, the existence of histone arginine demethylases is highly controversial. Here, we performed a high-content cell-based screening of a cDNA library containing 2,500 nuclear proteins and identified RDMe1 as a histone arginine demethylase. Overexpression of RDMe1 in HEK293T cells reduces H3R2me1/2a and H4R3me1/2a levels. In vitro, RDMe1 specifically demethylates H3R2me1/2a and H4R3me1/2a, and generates formaldehyde and succinate. The enzymatic activity requires Fe(II) and α-ketoglutarate as cofactors. RDMe1 is mainly located in the nucleolar and regulates rRNA transcription by demethylating H3R2me2a. ChIP-seq reveals that RDMe1 demethylates H4R3me2a in the promoter in a genome-wide scale. NMR reveals that RDMe1 binds iron and substrate peptides with N and C termini, respectively. Mutation of the iron binding residues abolished the binding and the demethylase activity. Thus, we identify a histone arginine demethylase and reveal the reversibility of arginine methylation. Examination of RDMe1 binding and histone H4R3me2a modification in control and RDMe1 knockdown cells.