Notes: The authors demonstrated the use of the luminescent MTase-Glo™ Methyltransferase Assay for assaying the activity of a broad range of methyltransferases. Using protein and DNA methyltransferases with peptide, dsDNA oligos, mononucleosome and oligonucleosome substrates, methyltransferase reactions were performed in 384-well plates and activity determined by adding the two MTase-Glo™ Assay reagents and light detected using a luminometer. When the methyltransferase inhibitor GSK126 was used with the EZH2 complex in the MTase-Glo™ Assay, the IC₅₀ value was similar to that reported in the literature. The Z´ value generated using MTase-Glo™ with EHMT2-G9a and either a full length histone H3 or H3-derived peptide substrate was greater than 0.5. When screening the LOPAC library for potential MTase-Glo™ Assay inhibitors, few were found, showing the assay performed well in HTS applications. (4650)