Histone Deacetylase (HDACs) have been described as six or seven different groups in mammals. HDAC1, HDAC2 and HDAC3 are like yeast Rpd3 protein, while HDAC4, HDAC5 and HDAC6 are like yeast Hda1 (Histone Deacetylase 1) protein.
Histone acetylation is a dynamic process whose levels are determined by the net activities of Histone acetyl transferase (HATs) and the competing enzymes histone deacetylases (HDACs). Both activities are associated with the nuclear matrix. Histone deacetylases activities were often, but not always, associated with transcriptional repression and nucleosome condensations. HDAC1, HDAC2 and several other HDACs are the catalytic subunits of different multiprotein regulatory complexes.
