Secretion and transcriptional regulation of transforming growth factor-beta 3 during myogenesis.
Transforming growth factor-beta 3 (TGF-beta 3) mRNA is differentially expressed in developing and mature mouse tissues, including high-level expression in developing and adult cardiac tissue. We show now that TGF-beta 3 mRNA is also expressed highly in skeletal muscle as well as in the mouse skeletal myoblast cell line C2C12. We also show that C2C12 cells secrete TGF-beta 3, and that this TGF-beta is able to inhibit C2C12 myoblast fusion after activation. In order to begin to understand how the TGF-beta 3 promoter is regulated in specific tissues during development, we therefore studied the regulation of TGF-beta 3 during myoblast fusion. After fusion of C2C12 cells into myotubes, TGF-beta 3 mRNA levels increased eightfold as a result of increased TGF-beta 3 transcription. TGF-beta 3 transcriptional regulation was studied in myoblasts and myotubes by transfection of chimeric TGF-beta 3/CAT promoter plasmids. Chloramphenicol acetyltransferase (CAT) activity was stimulated in myoblasts by several upstream regions between -301 and -47 of the TGF-beta 3 promoter and by the TGF-beta 3 5' untranslated region. CAT activity directed by the TGF-beta 3 promoter in myotubes was stimulated by a distinct upstream region located between -499 and -221. Therefore, the high level of TGF-beta 3 mRNA expression in muscle cells appears to be dependent on multiple regulatory events during different stages of myogenesis.
Lafyatis
R
R
Laboratory of Chemoprevention, National Cancer Institute, Bethesda, Maryland 20892.
Lechleider
R
R
Roberts
A B
AB
Sporn
M B
MB
D000818:Animals; D002454:Cell Differentiation; D002459:Cell Fusion; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D007700:Kinetics; D051379:Mice; D009132:Muscles / Q000166:cytology* / Q000502:physiology; D010957:Plasmids; D011401:Promoter Regions, Genetic; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000096:biosynthesis / Q000235:genetics* / Q000302:isolation & purification
D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D012313:RNA; D015500:Chloramphenicol O-Acetyltransferase