Fig. 7. Immunoprecipitation (IP) with Ezh2 antibodies shows histone methyltransferase (HMTase) activity for K9 and K27. (A) HMTase activity was tested on two different types of peptides with various combinations of lysine methylation. (B) HMTase assay of Ezh2 IP from ES cell extract on peptides as substrate. The immunoprecipitate showed highest HMTase activity for K27-unmethylated peptides and a lower activity for peptides, which were unmethylated at K9 but fully methylated at K4. (C) Western blot analysis of IP-bound beads and supernatant (SN) showed that the Ezh2 antibodies precipitate Ezh2 and that Eed and HDAC1 are bound to this complex.