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Histone deacetylase 4 Histone deacetylase 4 is a class IIa Zn-dependent enzyme that catalyzes hydrolysis of an N(6)-acetyl-lysine residue of a histone to yield a deacetylated histone (EC 3.5.1.98). Histone acetylation/deacetylation process is important for mediation of transcriptional regulation of many genes. Histone deacetylases usually act via association with DNA binding proteins to target specific chromatin regions. Class IIa histone deacetylases are signal-dependent co-repressors, having N-terminal regulatory domain with two or three conserved serine residues; phosphorylation of these residues is important for ability to shuttle between the nucleus and cytoplasm and act as transcriptional co-repressors. HDAC4 participates in regulation of chondrocyte hypertrophy and skeletogenesis. However, biological substrates for HDAC4 have not been identified; only low lysine deacetylation activity has been demonstrated and active site mutant has enhanced activity toward acetylated lysines. HDAC4 does not bind DNA directly, but through transcription factors MEF2C (myocyte enhancer factor-2C) and MEF2D. Other known interaction partners of the protein are 14-3-3 proteins, SMRT and N-CoR co-repressors, BCL6, HP1, SUMO-1 ubiquitin-like protein, and ANKRA2. It appears to interact in a multiprotein complex with RbAp48 and HDAC3. Furthermore, HDAC4 is required for TGFbeta1-induced myofibroblastic differentiation.
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