Histon Deactetylases (HDACs) are overexpressed and show very high activities in a number of tumor cells. Expression of HDAC1, -5, and -7 can be even used as a cancer biomarker. Moreover, they play a crucial role in oncogene expression.
HDACs remove acetyl groups from N acetyl lysine residues in histones. These enzymes belong to a number of enzymes which control the condensation status of nucleosomes (structure of a mono nucleosome is shown in Fig.1). While acetylation of histones by Histone acetyltransferases leads to decondensation and thus allows DNA binding proteins to interact with exposed sites to activate gene transcription, the activity of HDACs allows histones to wrap the DNA more tightly.