Negative Regulation of Histone Deacetylase 8 Activity by Cyclic AMP-Dependent Protein Kinase A

Abstract

Histone deacetylases (HDACs) are enzymes that catalyze the removal of acetyl groups from lysine residues of histone and nonhistone proteins. Recent studies suggest that they are key regulators of many cellular events, including cell proliferation and cancer development. Human class I HDACs possess homology to the yeast RPD3 protein and include HDAC1, HDAC2, HDAC3, and HDAC8. While HDAC1, HDAC2, and HDAC3 have been characterized extensively, almost nothing is known about HDAC8. Here we report that HDAC8 is phosphorylated by cyclic AMP-dependent protein kinase A (PKA) in vitro and in vivo. The PKA phosphoacceptor site of HDAC8 is Ser³⁹, a nonconserved residue among class I HDACs. Mutation of Ser³⁹ to Ala enhances the deacetylase activity of HDAC8. In contrast, mutation of Ser³⁹ to Glu or induction of HDAC8 phosphorylation by forskolin, a potent activator of adenyl cyclase, decreases HDAC8's enzymatic activity. Remarkably, inhibition of HDAC8 activity by hyperphosphorylation leads to hyperacetylation of histones H3 and H4, suggesting that PKA-mediated phosphorylation of HDAC8 plays a central role in the overall acetylation status of histones.

We thank Erding Hu and Stefan Kass for the HDAC8 cDNA, Wen Long Bai and Nancy Olashaw for discussion and critical reading of the manuscript, and the Moffitt Cancer Center Core Facility for technical support.

This work was supported by grants from the NIH (GM58486 and GM64850) and the Kaul Foundation to E.S. H.L. is a recipient of an American Heart Association postdoctoral fellowship.