Mechanisms of human histone and nucleic acid demethylases

► Methylation and demethylation are important modifications to proteins and nucleic acids. ► Methylation cycles play important roles in regulation of structure and function. ► Mechanisms of demethylases can be divided into two broad classes: nucleophilic and oxidative. ► The recent discovery of new demethylases highlights the possibility of as yet unidentified classes of demethylases.