Abstract
Histone deacetylases perform an important role in the regulation of transcription by modifying the histone components of chromatin. This imparts specific restrictions to transcription and contributes to the proper coordination of gene expression. In order to perform these functions and to achieve proper modulation of their activity, HDACs associate with other proteins, and in some cases, even with themselves. The purification and analyses of these complexes during the last few years has changed our view of the functions of these enzymes, as well as how they are regulated and interconnect with other chromatin-related activities. We are starting to understand how a limited number of HDACs can perform such a variety of functions. Here we review all the known HDAC-containing complexes including classes I, II, and III and we summarize the implications of their composition to the function for HDACs in vivo.