EZH2 (Enhancer of zeste homolog 2) is a histone-lysine N-methyltransferase enzyme EZH2 that participates in DNA methylation and, ultimately, transcriptional repression. EZH2 catalyzes the addition of methyl groups to histone H3 at lysine 27, by using the cofactor S-adenosyl-L-methionine. Methylation activity of EZH2 facilitates heterochromatin formation thereby silences gene function. Remodeling of chromosomal heterochromatin by EZH2 is also required during cell mitosis. Mutation or over-expression of EZH2 has been linked to many forms of cancer.