The catalytic activity of HDAC3 is necessary for a normal rate of cellular proliferation

Abstract

Histone deacetylases (HDACs) are enzymes that regulate chromatin structure through removal of acetyl groups from lysine residues on histones. HDAC3 is a unique member of class 1 HDACs that is a critical component of the SMRT/N-CoR co-repressor complex. Interestingly, Hdac3 deletion in immortalized NIH 3T3 cells results in decreased rates of cellular proliferation. Therefore, structure function studies were carried out in order to understand the mechanism by which Hdac3 regulates cell growth. A homology model and crystal structure were used to provide insight into the surface of HDAC3 and potential protein interaction regions. With this information in hand, mutations in HDAC3 were generated to disrupt HDAC3 protein interactions, eliminate HDAC3 deacetylase activity, and remove the ability of HDAC3 to undergo phosphorylation. HDAC3 mutants generated were expressed in Hdac3-/- NIH 3T3 cells, and their ability to complement the observed growth defect was monitored. While HDAC3-mediated changes in proliferation were not dependent upon phosphorylation, RelA binding, or protein interactions with hydrophobic regions, catalytic activity was required for normal growth rates. Furthermore, HDAC3 catalytic activity was dependent on its interaction with the deacetylase activating domain of SMRT/N-CoR mediated through Ins(1,4,5,6)P4. Therefore, HDAC3-mediated effects on cell growth are dependent on functional deacetylase activity and interaction with SMRT/N-CoR.