Identification of JmjC domain-containing UTX and JMJD3 as histone H3 lysine 27 demethylases

Covalent modifications of histones, such as acetylation and methylation, play important roles in the regulation of gene expression. Histone lysine methylation has been implicated in both gene activation and repression, depending on the specific lysine (K) residue that becomes methylated and the state of methylation (mono-, di-, or trimethylation). Methylation on K4, K9, and K36 of histone H3 has been shown to be reversible and can be removed by site-specific clemethylases. However, the enzymes that antagonize methylation on K27 of histone H3 (H3K27), an epigenetic mark important for embryonic stem cell maintenance, Polycombmediated gene silencing, and X chromosome inactivation have been elusive. Here we show the JmjC domain-containing protein UTX (ubiquitously transcribed tetratricopepticle repeat, X chromosome), as well as the related JMJID3 aumonji domain containing 3), specifically removes methyl marks on H3K27 in vitro. Further, the clemethylase activity of UTX requires a catalytically active JmjC domain. Finally, overexpression of UTX and JMJD3 leads to reduced di- and trimethylation on H3K27 in cells, suggesting that UTX and JMJD3 may function as H3K27 clemethylases in vivo. The identification of UTX and JMJID3 as H3K27-specific clemethylases provides direct evidence to indicate that similar to methylation on K4, K9, and K36 of histone H3, methylation on H311 < 27 is also reversible and can be dynamically regulated by site-specif ic histone methyltransferases and clemethylases.