Regulation of Histone Deacetylase 4 by Binding of 14-3-3 Proteins

Abstract

Histone (de)acetylation is important for the regulation of fundamental biological processes such as gene expression and DNA recombination. Distinct classes of histone deacetylases (HDACs) have been identified, but how they are regulated in vivo remains largely unexplored. Here we describe results demonstrating that HDAC4, a member of class II human HDACs, is localized in the cytoplasm and/or the nucleus. Moreover, we have found that HDAC4 interacts with the 14-3-3 family of proteins that are known to bind specifically to conserved phosphoserine-containing motifs. Deletion analyses suggested that S246, S467, and S632 of HDAC4 mediate this interaction. Consistent with this, alanine substitutions of these serine residues abrogated 14-3-3 binding. Although these substitutions had minimal effects on the deacetylase activity of HDAC4, they stimulated its nuclear localization and thus led to enhanced transcriptional repression. These results indicate that 14-3-3 proteins negatively regulate HDAC4 by preventing its nuclear localization and thereby uncover a novel regulatory mechanism for HDACs.Specific lysine acetylation of histones and nonhistone proteins has been recently recognized as a major mechanism by which eukaryotic transcription is regulated (12,23,24,44,45,56,57). Such acetylation is reversible and dynamic in vivo, and its level is governed by the opposing actions of histone acetyltransferases and histone deacetylases (HDACs). Distinct classes of HDACs have been identified in mammals (21, 36). Class I HDACs (HDAC1, HDAC2, HDAC3, and HDAC8) are homologous to yeast Rpd3 (8,16,49,60,61). HDAC1 and HDAC2 interact with each other and form the catalytic core of Sin3 and NuRD complexes, both of which play important roles in transcriptional repression and gene silencing (26,51,53,54,58,(63)(64)(65). Various transcriptional repressors recruit these complexes to inhibit transcription (reviewed in references 15, 45, and 56). Class II HDACs (HDAC4, HDAC5, HDAC6, and HDAC7) contain domains significantly similar to the catalytic domain of yeast Hda1 (9,11,20,33,41,52,55). HDAC4, HDAC5, and HDAC7 are homologous, whereas HDAC6 has two Hda1-related catalytic domains and a unique Cys-and Hisrich C-terminal domain. HDAC4 and HDAC5 interact with the MEF2 transcription factors (28,33,55), and this interaction is regulated (30, 62). Related to this, MITR/HDRP, a protein related to the N-terminal part of HDAC4, HDAC5, and HDAC7, binds to MEF2s and represses transcription (43,66). Moreover, HDAC4, HDAC5, and HDAC7 were found to interact with the nuclear receptor corepressors 17,20). These new findings suggest that like class I HDACs, some class II HDACs are recruited to promoters to inhibit transcription. One interesting but unaddressed question is how the function of HDACs is regulated in vivo.While HDAC1, HDAC2, and HDAC3 are nuclear, the plant deacetylase HD2 is a nucleolar protein (8, 31). Miska et al. reported that the HDAC4 protein lacking the N-terminal 117 residues is cytoplasmic or nuclear in HeLa cells (33), whereas Fischl...

Class II histone deacetylases: versatile regulators

“…All class IIa HDACs shuttle between the nucleus and the cytoplasm [6,20,21,23,26,[38][39][40]. Class IIa HDACs bind to 14-3-3 proteins, a family of highly conserved acidic proteins (reviewed in Ref.…”

“…This binding is dependent on the phosphorylation of two or three conserved N-terminal serine residues in class IIa HDACs and mediates their cytoplasmic sequestration (Fig. 1b) [20,21,23]; mutation of these sites prevents the export of class IIa HDACs from the nucleus to the cytoplasm [20 -24,40,42] (Fig. 1b).…”

Class IIa histone deacetylases: regulating the regulators

“…In response to various stimuli, a set of serine residues in the adapter domain of class IIa HDACs is phosphorylated, creating docking sites for the 14-3-3 proteins (Grozinger and Schreiber, 2000;Wang et al, 2000). Association with 14-3-3 induces nuclear export and cytoplasmic accumulation of class IIa HDACs with concomitant derepression of their target promoters (Grozinger and Schreiber, 2000;Wang et al, 2000;Kao et al, 2001;Liu et al, 2005).…”

“…Simultaneous mutations of Class IIa histone deacetylases M Martin et al these serine residues into alanines totally abolished interaction between HDAC5/9 and 14-3-3 Zhang et al, 2002a). Unexpectedly, the corresponding serine-to-alanine double mutants of HDAC4 and HDAC7 retained residual 14-3-3 binding (McKinsey et al, 2000a, b;Wang et al, 2000;Kao et al, 2001). This observation led to the identification of Ser 632 in HDAC4 and Ser 449 in HDAC7 as additional 14-3-3 binding sites (Grozinger and Schreiber, 2000;McKinsey et al, 2000a;Wang et al, 2000;Kao et al, 2001;Dequiedt et al, 2003).…”

“…However, depending on cell lines examined, a significant portion of the molecules can also be found in the cytoplasm, suggesting that these enzymes may shuttle between the nucleus and the cytoplasm Fischle et al, 2001). Early confocal microscopy experiments with leptomycin B and recently using the fluorescence loss in photobleaching technology confirmed that class IIa HDACs are subject to CRM1-dependent nuclear export Grozinger and Schreiber, 2000;Wang et al, 2000;Kao et al, 2001;Dequiedt et al, 2006). Cytoplasmic accumulation of class IIa HDACs renders them unable to impact on transcription since it sequesters them away from their histone substrates and renders them enzymatically inactive as HDACs (Fischle et al, 2001(Fischle et al, , 2002.…”