Myogenic basic helix-loop-helix proteins regulate the expression of peroxisomal proliferator activated receptor-gamma coactivator-1alpha.
Peroxisomal proliferator-activated receptor-gamma coactivator-1alpha (PGC-1alpha), a transcriptional coactivator, is selectively expressed in slow-twitch fibers in skeletal muscle. Ectopic expression of the PGC-1alpha gene in either a cell or an animal has been shown to promote fast to slow fiber-type switch. The expression of PGC-1alpha in muscle is regulated by myocyte enhancer factor 2 and Forkhead in rhabdomyosarcoma, two transcription factors implicated in terminal muscle differentiation. In this study we found that PGC-1alpha expression was activated during terminal muscle differentiation in both C2C12 and Sol8 myoblasts. Using retrovirus-mediated MyoD overexpression in C3H10T1/2 cells, we also demonstrated that MyoD, the master regulator of terminal differentiation, could activate PGC-1alpha expression in vivo. Our transient transfection results also show that myogenic basic helix-loop-helix (bHLH) proteins, especially MyoD, can activate PGC-1alpha expression by targeting its promoter. Myogenic bHLH protein target sites on PGC-1alpha promoter were localized to a short region (-49 to approximately +2) adjacent to the transcription start site, which contains two putative E boxes. Mutation of either site significantly reduced MyoD-mediated transactivation in the cells, suggesting that both sites are required for myogenic bHLH protein-mediated activation. However, only one site, the E2 box, was directly bound by glutathione-S-transferase-MyoD protein in EMSAs. Our results indicate that myogenic bHLH proteins not only are involved in lineage determination and terminal differentiation, but also are directly implicated in activation of the key fiber-type and metabolic switch gene, PGC-1alpha.
Chang
Ju Hui
JH
Department of Life Sciences, National Central University, Jhongli 32054, Taiwan, Republic of China.
Lin
Kwang Huei
KH
Shih
Chung Hsuan
CH
Chang
Yu Jung
YJ
Chi
Hsiang Chung
HC
Chen
Shen Liang
SL
D000818:Animals; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins / Q000502:physiology*; D002454:Cell Differentiation; D019070:Cell Lineage; D002478:Cells, Cultured; D005786:Gene Expression Regulation; D006360:Heat-Shock Proteins / Q000235:genetics* / Q000502:physiology; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D017570:MyoD Protein / Q000502:physiology; D032448:Myoblasts, Skeletal / Q000166:cytology*; D018006:Myogenic Regulatory Factors / Q000378:metabolism; D018008:Myogenin / Q000502:physiology; D009687:Nuclear Proteins / Q000378:metabolism; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000235:genetics* / Q000502:physiology
D051792:Basic Helix-Loop-Helix Proteins; D006360:Heat-Shock Proteins; D017570:MyoD Protein; D018006:Myogenic Regulatory Factors; D018008:Myogenin; D009687:Nuclear Proteins; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D014157:Transcription Factors; C057363:MyoD1 myogenic differentiation protein; C486497:PPARGC1A protein, human