Abstract
Mirk/dyrk1B is a member of the dyrk/minibrain family of serine/threonine kinases that mediate the transition from growth to differentiation in lower eukaryotes and mammals. Depletion of endogenous Mirk from C2C12 myoblasts by RNA interference blocks skeletal muscle differentiation (Deng, X., Ewton, D., Pawlikowski, B., Maimone, M., and Friedman, E. (2003) J. Biol. Chem. 278, 41347-41354). We now demonstrate that knockdown of Mirk blocks transcription of the muscle regulatory factor myogenin. Co-expression of Mirk with MEF2C, but not MyoD or Myf5, enhanced activation of the myogenin promoter in a Mirk kinase-dependent manner. Mirk activated MEF2 not through direct phosphorylation of MEF2 but by phosphorylation of its inhibitors, the class II histone deacetylases (HDACs). MEF2 is sequestered by class II HDACs such as HDAC5 and MEF2-interacting transcriptional repressor (MITR). Mirk antagonized the inhibition of MEF2C by MITR, whereas kinase-inactive Mirk was ineffective. Mirk phosphorylates class II HDACs at a conserved site within the nuclear localization region, reducing their nuclear accumulation in a dose-dependent and kinase-dependent manner. Moreover, less mutant MITR phosphomimetic at the Mirk phosphorylation site localized in the nucleus than wild-type MITR. Regulation of class II HDACs occurs by multiple mechanisms. Others have shown that calcium signaling leads to phosphorylation of HDACs at 14-3-3-binding sites, blocking their association with MEF2 within the nucleus. Mirk provides another level of regulation. Mirk is induced within the initial 24 h of myogenic differentiation and enables MEF2 to transcribe the myogenin gene by decreasing the nuclear accumulation of class II HDACs.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Sequence
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Animals
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Binding Sites
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Blotting, Northern
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Butyrates / pharmacology
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Cell Differentiation
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Cell Line
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Cell Nucleus / metabolism*
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DNA / chemistry
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DNA-Binding Proteins / metabolism
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Dose-Response Relationship, Drug
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Down-Regulation
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Dyrk Kinases
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Electrophoresis, Polyacrylamide Gel
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Gene Expression Regulation, Enzymologic*
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Glutathione Transferase / metabolism
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Histone Deacetylases / metabolism*
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Luciferases / metabolism
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MEF2 Transcription Factors
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Mice
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Mitogen-Activated Protein Kinases / biosynthesis*
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Molecular Sequence Data
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Muscle Proteins / metabolism
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Muscle, Skeletal / cytology*
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Muscle, Skeletal / metabolism
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MyoD Protein / metabolism
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Myogenic Regulatory Factor 5
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Myogenic Regulatory Factors / metabolism
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Myogenin / genetics
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Myogenin / metabolism*
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NIH 3T3 Cells
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Oligonucleotide Array Sequence Analysis
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Phosphorylation
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Plasmids / metabolism
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Promoter Regions, Genetic
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Protein Serine-Threonine Kinases / biosynthesis*
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Protein-Tyrosine Kinases / biosynthesis*
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RNA Interference
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RNA, Messenger / metabolism
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RNA, Small Interfering / metabolism
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Recombinant Fusion Proteins / metabolism
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Sequence Homology, Amino Acid
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Subcellular Fractions
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Trans-Activators / metabolism
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Transcription Factors
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Transcription, Genetic
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Transfection
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Up-Regulation
Substances
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Butyrates
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DNA-Binding Proteins
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MEF2 Transcription Factors
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Mef2c protein, mouse
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Muscle Proteins
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Myf5 protein, mouse
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MyoD Protein
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Myog protein, mouse
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Myogenic Regulatory Factor 5
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Myogenic Regulatory Factors
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Myogenin
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RNA, Messenger
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RNA, Small Interfering
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Recombinant Fusion Proteins
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Trans-Activators
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Transcription Factors
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DNA
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Luciferases
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Glutathione Transferase
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Protein-Tyrosine Kinases
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Protein Serine-Threonine Kinases
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Mitogen-Activated Protein Kinases
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Histone Deacetylases