Cyclin D-cdk4 activity modulates the subnuclear localization and interaction of MEF2 with SRC-family coactivators during skeletal muscle differentiation.
Prior work has indicated that D-type cyclin-cdk4 complexes, which are only active in proliferating cells, can suppress the skeletal muscle differentiation program in proliferating myoblasts. In this study, we show that cyclin D-cdk activity can block the activity of the MEF2 family of transcriptional regulators, which are crucial regulators of skeletal muscle gene expression. We have found that cyclin D-cdk activity blocks the association of MEF2C with the coactivator protein GRIP-1 and thereby inhibits the activity of MEF2. During skeletal muscle differentiation, GRIP-1 is localized to punctate nuclear structures and can apparently tether MEF2 to such structures. Cotransfection of GRIP-1 can both potentiate the transcriptional activity of a Gal4-MEF2C construct and induce MEF2C localization to punctate nuclear structures. Consistent with the absence of punctate nuclear GRIP-1 in proliferating myoblasts, we have found that ectopic cyclin D-cdk4 expression disrupts the localization of both GRIP-1 and MEF2C to these punctate subnuclear structures. Our findings indicate that cyclin D-cdk4 activity represses skeletal muscle differentiation in proliferating cells by blocking the association of MEF2 with the coactivator GRIP-1 and concomitantly disrupts the association of these factors with punctate nuclear subdomains within the cell.
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA.
Jean-Bernard
JB
Lazaro
Peter J
PJ
Bailey
Andrew B
AB
Lassar
D016475:3T3 Cells; D000818:Animals; D001692:Biological Transport; D019556:COS Cells; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002454:Cell Differentiation; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002522:Chlorocebus aethiops; D019938:Cyclin D1 / Q000235:genetics / Q000378:metabolism; D056742:Cyclin D2; D056743:Cyclin D3; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases / Q000235:genetics / Q000378:metabolism*; D016213:Cyclins / Q000235:genetics / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018257:Helix-Loop-Helix Motifs; D006655:Histone Deacetylases / Q000235:genetics / Q000378:metabolism; D064326:MEF2 Transcription Factors; D051379:Mice; D018482:Muscle, Skeletal / Q000166:cytology*; D018006:Myogenic Regulatory Factors / Q000235:genetics / Q000378:metabolism*; D051958:Nuclear Receptor Coactivator 2; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection
C486196:Ccnd2 protein, mouse; C534697:Ccnd3 protein, mouse; D056742:Cyclin D2; D056743:Cyclin D3; D016213:Cyclins; D004268:DNA-Binding Proteins; D064326:MEF2 Transcription Factors; C578041:Mef2c protein, mouse; D018006:Myogenic Regulatory Factors; C498002:Ncoa2 protein, mouse; D051958:Nuclear Receptor Coactivator 2; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D019938:Cyclin D1; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C517685:Camk4 protein, mouse; C495902:Cdk4 protein, mouse; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases; C543274:Hdac7 protein, mouse; D006655:Histone Deacetylases