Histone deacetylase 3 (HDAC3) activity is regulated by interaction with protein serine/threonine phosphatase 4

Abstract

Histone deacetylase 3 (HDAC3) is one of four members of the human class I HDACs that regulates gene expression by deacetylation of histones and nonhistone proteins. Early studies have suggested that HDAC3 activity is regulated by association with the corepressors N-CoR and SMRT. Here we demonstrate that, in addition to protein-protein interactions with NCoR/SMRT, the activity of HDAC3 is regulated by both phosphorylation and dephosphorylation. A protein kinase CK2 phosphoacceptor site in the HDAC3 protein was identified at position Ser 424 , which is a nonconserved residue among the class I HDACs. Mutation of this residue was found to reduce deacetylase activity. Interestingly, unlike other class I HDACs, HDAC3 uniquely copurifies with the catalytic and regulatory subunits of the protein serine/threonine phosphatase 4 complex (PP4 c /PP4 R1 ). Furthermore, HDAC3 complexes displayed protein phosphatase activity and a series of subsequent mutational analyses revealed that the N terminus of HDAC3 (residues 1-122) was both necessary and sufficient for HDAC3-PP4 c interactions. Significantly, both overexpression and siRNA knock-down approaches, and analysis of cells devoid of PP4 c , unequivocally show that HDAC3 activity is inversely proportional to the cellular abundance of PP4 c . These findings therefore further highlight the importance of protein-protein interactions and extend the significance of dephosphorylation in the regulation of HDAC activity, as well as present a novel alternative pathway by which HDAC3 activity is regulated.

Conditional Knockout Mice Reveal an Essential Role of Protein Phosphatase 4 in Thymocyte Development and Pre-T-Cell Receptor Signaling

“…Specifically, our previous studies have demonstrated that PP4 interacts with, dephosphorylates, and activates HPK1 (30), an upstream kinase known to regulate T-cell activation and apoptosis (1,20). Moreover, PP4 associates with, dephosphorylates, and inhibits histone deacetylase 3 (29), which was originally cloned from phytohemagglutinin-activated T cells and whose mRNA is upregulated in peripheral blood mononuclear cells cultured with anti-CD3 antibody (3). PP4 also associates with its regulatory subunit ␣4 to regulate mammalian target-of-rapamycin (mTOR) signaling, which has been shown to be required for anti-CD3-and anti-CD28-induced, IL-2-independent T-cell proliferation and is also important for T-cell survival (2,17).…”

“…PP4 interacts with and downregulates insulin receptor substrate 4 following tumor necrosis factor alpha stimulation (21) and is involved in tumor necrosis factor alpha-induced activation of the Jun N-terminal protein kinase signaling pathway (31). Furthermore, PP4 physically associates with, dephosphorylates, and inhibits histone deacetylase 3 activity (29). Saccharomyces cerevisiae strains mutated for Pph3 (PP4 ortholog), but not Pph22 (PP2A ortholog), become hypersensitive to the cancer drug cisplatin, suggesting a role for PP4 in DNA damage signaling (5).…”

HDAC3: taking the SMRT-N-CoRrect road to repression

“…Ser424 of HDAC3 could be phosphorylated by CK2 and dephosphorylated by protein serine/threonine phosphatase 4 (Zhang et al, 2005b). The latter copurifies with the N-CoR complex and interacts with the N terminus of HDAC3 (Zhang et al, 2005b).…”

Leucine Carboxyl Methyltransferase 1 (LCMT-1) Methylates Protein Phosphatase 4 (PP4) and Protein Phosphatase 6 (PP6) and Differentially Regulates the Stable Formation of Different PP4 Holoenzymes

“…The PP4R1-PP4c complex down-regulates HDAC3 activity by dephosphorylation at Ser-424 (49). To determine whether reduction in the methylation-dependent PP4R1-PP4c complex due to LCMT-1 knock-out has physiological consequences on HDAC3, cell lysates of WT and LCMT-1 KO MEFs were analyzed for phosphorylation of HDAC3 at Ser-424.…”