Histone posttranslational modifications are among the epigenetic mechanisms that 
modulate chromatin structure and gene transcription. Histone methylation and 
demethylation are dynamic processes controlled respectively by histone 
methyltransferases (HMTs) and demethylases (HDMs). Several HMTs and HDMs have 
been implicated in cancer, inflammation, and diabetes, making them attractive 
targets for drug therapy. Hence, the discovery of small-molecule modulators for 
these two enzyme classes has drawn significant attention from the pharmaceutical 
industry. Herein, the authors describe the development and optimization of 
homogeneous LANCE Ultra and AlphaLISA antibody-based assays for measuring the 
catalytic activity of two epigenetic enzymes acting on lysine 4 of histone H3: 
SET7/9 methyltransferase and LSD1 demethylase. Both the SET7/9 and LSD1 assays 
were designed as signal-increase assays using biotinylated peptides derived from 
the N-terminus of histone H3. In addition, the SET7/9 assay was demonstrated 
using full-length histone H3 protein as substrate in the AlphaLISA format. 
Optimized assays in 384-well plates are robust (Z' factors ≥0.7) and sensitive, 
requiring only nanomolar concentrations of enzyme and substrate. All assays 
allowed profiling of known SET7/9 and LSD1 inhibitors. The results demonstrate 
that the optimized LANCE Ultra and AlphaLISA assay formats provide a relevant 
biochemical screening approach toward the identification of small-molecule 
inhibitors of HMTs and HDMs that could lead to novel epigenetic therapies.