In the nucleus, DNA is tightly packaged into higher-order structures, generating an environment that is highly repressive towards DNA processes such as gene transcription. Acetylation of lysine residues within proteins has recently emerged as a major mechanism used by the cell to overcome this repression. Acetylation of non-histone proteins, including transcription factors, as well as histones, appears to be involved in this process. Like phosphorylation, acetylation is a dynamic process that can regulate protein-DNA and protein-protein interactions. Moreover, a conserved domain, the bromodomain, has been implicated in the binding of acetylated peptides, suggesting a role for acetylation in intracellular signalling.