Histone methylation has important roles in regulating gene expression and forms part of the
epigenetic memory system that regulates cell fate and identity. Enzymes that directly remove
methyl marks from histones have recently been identified, revealing a new level of plasticity
within this epigenetic modification system. Here we analyse the evolutionary relationship
between Jumonji C (JmjC)-domain-containing proteins and discuss their cellular functions in
relation to their potential enzymatic activities.