A Dynamic Role for HDAC7 in MEF2-mediated Muscle Differentiation

Abstract

The overlapping expression profile of MEF2 and the class-II histone deacetylase, HDAC7, led us to investigate the functional interaction and relationship between these regulatory proteins. HDAC7 expression inhibits the activity of MEF2 (-A, -C, and -D), and in contrast MyoD and Myogenin activities are not affected. Glutathione S-transferase pulldown and immunoprecipitation demonstrate that the repression mechanism involves direct interactions between MEF2 proteins and HDAC7 and is associated with the ability of MEF2 to interact with the N-terminal 121 amino acids of HDAC7 that encode repression domain 1. The MADS domain of MEF2 mediates the direct interaction of MEF2 with HDAC7. MEF2 inhibition by HDAC7 is dependent on the N-terminal repression domain and surprisingly does not involve the C-terminal deacetylase domain. HDAC7 interacts with CtBP and other class-I and -II HDACs suggesting that silencing of MEF2 activity involves corepressor recruitment. Furthermore, we show that induction of muscle differentiation by serum withdrawal leads to the translocation of HDAC7 from the nucleus into the cytoplasm. This work demonstrates that HDAC7 regulates the function of MEF2 proteins and suggests that this class-II HDAC regulates this important transcriptional (and pathophysiological) target in heart and muscle tissue. The nucleocytoplasmic trafficking of HDAC7 and other class-II HDACs during myogenesis provides an ideal mechanism for the regulation of HDAC targets during mammalian development and differentiation.Skeletal muscle has become a model for understanding many fundamental principles of development. Differentiation of precursor cells into skeletal muscle cells involves two events, determination into myoblasts and the formation of postmitotic, multinucleated myotubes with contractile phenotype. These processes are under control of members of the MyoD family of basic-helix-loop-helix (bHLH) 1 transcription factors (MyoD, Myf5, Myogenin, and MRF4). These proteins can inhibit cell proliferation, regulate a cascade of muscle-specific gene expression, auto-and cross-regulate their own and each other's expression, and induce muscle differentiation in nonmuscle cells (1-3). Myogenic bHLH proteins activate transcription of muscle-specific genes by forming heterodimers with other, ubiquitously expressed bHLH proteins known as E2A proteins (alternatively spliced products of the E2A gene) (4 -7). These heterodimers bind to the E box motif (CANNTG), which functions as the cognate binding site in the regulatory regions of most muscle genes (1,3,8). MyoD and Myf5 are required for determination of precursor cells into myoblasts (9), whereas Myogenin is specifically required for differentiation (10, 11). Therefore myoD and myf5 are expressed in proliferating myoblasts and are markers for commitment, whereas the expression of myogenin is a marker of terminal-differentiation.Even though members of the MyoD family are the key regulators of muscle differentiation, the activation of muscle-specific genes is dependent on the associat...

Histone deacetylase 7, a potential target for the antifibrotic treatment of systemic sclerosis

“…Nucleocytoplasmic shuttling has been observed for all class II HDACs and reflects a putatively important regulatory mechanism. However, it should be stressed that HDAC-7 is expressed in heart and lung tissues, placenta, pancreas, and skeletal muscle as well as in CD4/CD8 doublepositive thymocytes (34)(35)(36)(37). HDAC-7 -/-mouse embryos display defects in the development and integrity of blood vessels (38).…”

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.…”

“…HDAC4, -5, -7 and -9 interact with MEF2 proteins through a highly conserved 17 amino acid motif located in their N-termini [7,23,38,65,66]. Expression of an HDAC -VP16 fusion protein, in which the VP16 activation domain replaces the catalytic domain of HDAC4 or -5, enhances myogenic conversion [47].…”

Class IIa histone deacetylases: regulating the regulators

“…However, considering that lysine deacetylation is a prerequisite to methylation, two attractive models emerge. First, this interaction would allow the recruitment of a deacetylase/methyltransferase complex that would be important for the establishment and maintenance of transcriptional Sparrow et al, 1999;Verdel and Khochbin, 1999;Wang et al, 1999;Lemercier et al, 2000;Lu et al, 2000a, b;Dressel et al, 2001;Kao et al, 2001) NF-AT3C DNA-anchoring transcriptional factor (Dai et al, 2005) DnaJ ( (Zhang et al, 2002b). Alternatively, when bound to methylated histones, the HP1/HMTase complex could propagate a repressive chromatin state through class IIa HDACmediated deacetylation and subsequent methylation of adjacent nucleosomal histone tails.…”

“…Alternatively, when bound to methylated histones, the HP1/HMTase complex could propagate a repressive chromatin state through class IIa HDACmediated deacetylation and subsequent methylation of adjacent nucleosomal histone tails. On a similar vein, the N terminus of HDAC4, -5 and -9 comprises an interaction motif for the transcriptional corepressor CtBP (Dressel et al, 2001;Zhang et al, 2001a). Since CtBP is part of a higher-order complex containing chromatin-modifying enzymes such as class I HDACs and HMTs (Shi et al, 2003), it is tempting to speculate that class IIa HDACs might use CtBP to recruit multiple enzymatic activities to their target promoters.…”