Histone acetyltransferase (HAT) assays are analytical methods used to measure the enzymatic activity of histone acetyltransferases, enzymes that transfer acetyl groups from acetyl-coenzyme A (acetyl-CoA) to lysine residues on histone proteins. These assays are widely applied in epigenetics, chromatin biology, and drug discovery because HAT activity is closely associated with gene regulation and chromatin accessibility. They are also valuable tools for screening compounds that inhibit or modulate HAT function.

Principle of the Assay

The fundamental principle of a HAT assay is the detection of acetyl group transfer from acetyl-CoA to a histone substrate or histone-derived peptide. Depending on the assay format, the reaction product may be quantified using radioisotope labeling, fluorescence-based detection, or colorimetric readouts. These approaches support both mechanistic enzymology studies and high-throughput screening applications for inhibitor identification.

Common Assay Formats

HAT assays are available in several formats, including radiometric, fluorescent, and colorimetric systems.

• Radiometric Assays: Often considered a reference method because they directly measure acetyl transfer using labeled acetyl-CoA, providing high sensitivity and specificity.
• Fluorescent Assays: These assays enable rapid and sensitive detection without the use of radioactive materials and are compatible with automated laboratory workflows.
• Colorimetric Assays: Frequently used in routine laboratory applications due to their simplicity and compatibility with 96-well plate formats for efficient compound screening.