The Specificity and Regulation of Human Histone Deacetylase 8.

Abstract

Post-translational modifications (PTMs) of proteins increase the complexity of the proteome, alter protein function, and play important roles in cellular function. Lysine acetylation, catalyzed by lysine acetyltransferases, is an important post-translational modification of proteins, including histones, transcription factors, and cytoplasmic proteins. The modification is reversible; hydrolysis is catalyzed by histone deacetylases (HDACs). Lysine deacetylation is important for regulating cellular processes, and aberrant deacetylation is implicated in diseases including cancer. HDAC8 is a metal-dependent HDAC that is activated by Zn(II) and Fe(II) under in vitro conditions, and altering the metal ion identity affects activity. This enzyme is a therapeutic target for cancers, parasitic infection, and a developmental disorder; however, therapeutic research is impeded by the lack of knowledge regarding HDAC substrate recognition and regulation and by the challenge of identifying HDAC substrates and binding partners. My research has focused on the substrate specificity, metal dependence, and regulation by phosphorylation of HDAC8. I have shown that the sequence specificity of HDAC8 toward peptide substrates is dependent on the identity of the catalytic metal ion. Additionally, I have investigated regulation of HDAC8 by phosphorylation on residue Ser39, using the S39E mutant as a mimetic, demonstrating that this modification significantly alters metal binding properties of HDAC8, decreases HDAC8-catalyzed deacetylation of peptides, and alters substrate binding. I have shown that HDAC8 exhibits changes in substrate specificity for singly acetylated octamers and nucleosome in vitro, compared to peptide substrates representing the same sites. Elucidating the mechanisms that regulate HDAC8 substrate specificity is important for determining the role of this enzyme in normal and pathophysiological processes in the cell.