Bromodomains are a family of evolutionarily conserved protein modules of approximately 110 amino acids that have been found in chromatin-associated proteins as well as nuclear histone acetyltransferases (HATs). Besides its role in chromatin remodeling, recent studies have identified that bromodomains, as acetyl-lysine binding domains, are able to recognize and bind ε–N-acetylated lysine residues in histone and non-histone proteins. The nuclear magnetic resonance (NMR) spectroscopic analysis reveals that the chemical structure of bromodomains, consisting of four left-handed α-helices (including αZ, αA, αB and αC) connected by two loops (ZA and BC loops), forms a deep hydrophobic cavity serving as the acetyl-lysine recognition site.