Two of the unsolved but important questions in epigenetics are whether arginine demethylases (RDMs) exist and whether proteolytic cleavage of the histone tails and subsequent histone remodeling are a major epigenetic modification process. Jumonji domain (JmjC)-containing proteins have been characterized as lysine demethylases (KDMs) in a certain degree (Klose et al., 2006). Emerging evidences indicate that they also catalyze demethylation reaction on the arginine residues and proteolytic removal of histone tails. These processes are likely associated with biological meanings. This research highlight is intended to provide a bird’s eye view of the current state of the expanded biochemical properties of JmjC-containing proteins as...