In Vitro Histone Deacetylase Activity Screening: Making a Case for Better Assays

Recent advances in epigenetics and proteomics have emphasized the importance of protein acetylation and deacetylation in cellular homeostasis. Dynamic control of the acetylation states, by two functionally opposing enzymes - histone deacetylase (HDAC) and histone acetyltransferase (HAT) - has emerged as a key regulatory mechanism for more than 2000 proteins. HDAC-mediated disregulation of the protein deacetylation has been linked to various diseases, including cancer. Deconvoluting the collective and individual roles of HDAC isoforms, especially as they pertain to human pathological states, continues to be a focus for both academic and pharmaceutical laboratories. However, limitations of current HDAC activity assays temper progress in this growing field. In this chapter, we review various HDAC activity assays that have been developed, highlighting the strengths and weaknesses of each assay. We conclude by making a case for substrate-matched, label-free in vitro assays as desirable alternatives to the commonly used fluorescence-based HDAC activity assays.