Fluorescence-based methods for screening writers and readers of histone methyl marks.

The histone methyltransferase (HMT) family of proteins consists of enzymes that methylate lysine or arginine residues on histone tails as well as other proteins. Such modifications affect chromatin structure and play a significant regulatory role in gene expression. Many HMTs have been implicated in tumorigenesis and progression of multiple malignancies and play essential roles in embryonic development and stem cell renewal. Overexpression of some HMTs has been observed and is correlated positively with various types of cancer. Here the authors report development of a continuous fluorescence-based methyltransferase assay in a 384-well format and its application in determining kinetic parameters for EHMT1, G9a, PRMT3, SETD7, and SUV39H2 as well as for screening against libraries of small molecules to identify enzyme inhibitors. They also report the development of a peptide displacement assay using fluorescence polarization in a 384-well format to assay and screen protein peptide interactions such as those of WDR5 and EED, components of MLL and EZH2 methyltransferase complexes. Using these high-throughput screening methods, the authors have identified potent inhibitors and ligands for some of these proteins.