In vitro PRC2 activity of EZH2. Histone methyltransferase reaction was performed using 1.2μM biotinylated peptide substrate (ie, peptide mimicking the H3 tail, H3(21-44)), which has been unmethylated (H3K27me0, open bar or me0), monomethylated (H3K27me1, gray bar or me1) or dimethylated (H3K27me2, black bar or me2) at Lys-27. The reactions were incubated with purified 250 ng (A) or various amounts (B) of PRC-2 complex containing wild-type EZH2 (WT), EZH2 mutants (Y641N or Y641F). (A) Error bars represent SD of replicates from 2 independent experiments.