Lysine acetylation has been shown to occur in many protein targets, including 
core histones, about 40 transcription factors and over 30 other proteins. This 
modification is reversible in vivo, with its specificity and level being largely 
controlled by signal-dependent association of substrates with acetyltransferases 
and deacetylases. Like other covalent modifications, lysine acetylation exerts 
its effects through "loss-of-function" and "gain-of-function" mechanisms. Among 
the latter, lysine acetylation generates specific docking sites for bromodomain 
proteins. For example, bromodomains of Gcn5, PCAF, TAF1 and CBP are able to 
recognize acetyllysine residues in histones, HIV Tat, p53, c-Myb or MyoD. In 
addition to the acetyllysine moiety, the flanking sequences also contribute to 
efficient recognition. The relationship between acetyllysine and bromodomains is 
reminiscent of the specific recognition of phosphorylated residues by 
phospho-specific binding modules such as SH2 domains and 14-3-3 proteins. 
Therefore, lysine acetylation forges a novel signaling partnership with 
bromodomains to govern the temporal and spatial regulation of protein functions 
in vivo.