The transcriptional corepressor MITR is a signal-responsive inhibitor of myogenesis

CL Zhang, TA McKinsey… - Proceedings of the …, 2001 - National Acad Sciences
Proceedings of the National Academy of Sciences, 2001National Acad Sciences
Activation of muscle-specific genes by members of the myocyte enhancer factor 2 (MEF2)
and MyoD families of transcription factors is coupled to histone acetylation and is inhibited
by class II histone deacetylases (HDACs) 4 and 5, which interact with MEF2. The ability of
HDAC4 and-5 to inhibit MEF2 is blocked by phosphorylation of these HDACs at two
conserved serine residues, which creates docking sites for the intracellular chaperone
protein 14-3-3. When bound to 14-3-3, HDACs are released from MEF2 and transported to …
Activation of muscle-specific genes by members of the myocyte enhancer factor 2 (MEF2) and MyoD families of transcription factors is coupled to histone acetylation and is inhibited by class II histone deacetylases (HDACs) 4 and 5, which interact with MEF2. The ability of HDAC4 and -5 to inhibit MEF2 is blocked by phosphorylation of these HDACs at two conserved serine residues, which creates docking sites for the intracellular chaperone protein 14-3-3. When bound to 14-3-3, HDACs are released from MEF2 and transported to the cytoplasm, thereby allowing MEF2 to stimulate muscle-specific gene expression. MEF2-interacting transcription repressor (MITR) shares homology with the amino-terminal regions of HDAC4 and -5, but lacks an HDAC catalytic domain. Despite the absence of intrinsic HDAC activity, MITR acts as a potent inhibitor of MEF2-dependent transcription. Paradoxically, however, MITR has minimal inhibitory effects on the skeletal muscle differentiation program. We show that a substitution mutant of MITR containing alanine in place of two serine residues, Ser-218 and Ser-448, acts as a potent repressor of myogenesis. Our findings indicate that promyogenic signals antagonize the inhibitory action of MITR by targeting these serines for phosphorylation. Phosphorylation of Ser-218 and Ser-448 stimulates binding of 14-3-3 to MITR, disrupts MEF2:MITR interactions, and alters the nuclear distribution of MITR. These results reveal a role for MITR as a signal-dependent regulator of muscle differentiation.
National Acad Sciences