Molecular mechanisms of myogenic coactivation by p300: direct interaction with the activation domain of MyoD and with the MADS box of MEF2C.
By searching for molecules that assist MyoD in converting fibroblasts to muscle cells, we have found that p300 and CBP, two related molecules that act as transcriptional adapters, coactivate the myogenic basic-helix-loop-helix (bHLH) proteins. Coactivation by p300 involves novel physical interactions between p300 and the amino-terminal activation domain of MyoD. In particular, disruption of the FYD domain, a group of three amino acids conserved in the activation domains of other myogenic bHLH proteins, drastically diminishes the transactivation potential of MyoD and abolishes both p300-mediated coactivation and the physical interaction between MyoD and p300. Two domains of p300, at its amino and carboxy terminals, independently function to both mediate coactivation and physically interact with MyoD. A truncated segment of p300, unable to bind MyoD, acts as a dominant negative mutation and abrogates both myogenic conversion and transactivation by MyoD, suggesting that endogenous p300 is a required coactivator for MyoD function. The p300 dominant negative peptide forms multimers with intact p300. p300 and CBP serve as coactivators of another class of transcriptional activators critical for myogenesis, myocyte enhancer factor 2 (MEF2). In fact, transactivation mediated by the MEF2C protein is potentiated by the two coactivators, and this phenomenon is associated with the ability of p300 to interact with the MADS domain of MEF2C. Our results suggest that p300 and CBP may positively influence myogenesis by reinforcing the transcriptional autoregulatory loop established between the myogenic bHLH and the MEF2 factors.
Sartorelli
V
V
Institute for Genetic Medicine and Department of Biochemistry and Molecular Biology, University of Southern California School of Medicine, Los Angeles 90033, USA.
Huang
J
J
Hamamori
Y
Y
Kedes
L
L
D016475:3T3 Cells; D000123:Acetyltransferases; D000199:Actins / Q000235:genetics; D000818:Animals; D050882:CREB-Binding Protein; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation; D002460:Cell Line; D003402:Creatine Kinase / Q000235:genetics; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000235:genetics; D004268:DNA-Binding Proteins / Q000378:metabolism*; D018257:Helix-Loop-Helix Motifs; D017405:Herpes Simplex Virus Protein Vmw65 / Q000235:genetics; D051548:Histone Acetyltransferases; D006801:Humans; D026161:MADS Domain Proteins; D064326:MEF2 Transcription Factors; D051379:Mice; D018485:Muscle Fibers, Skeletal / Q000737:chemistry; D009132:Muscles / Q000737:chemistry / Q000166:cytology / Q000502:physiology*; D009154:Mutation; D017570:MyoD Protein / Q000235:genetics / Q000378:metabolism*; D018006:Myogenic Regulatory Factors / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D035381:TATA-Binding Protein Associated Factors; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D035362:Transcription Factor TFIID; D014157:Transcription Factors / Q000378:metabolism*; D050880:p300-CBP Transcription Factors; D000099224:p300-CBP-Associated Factor
D000123:Acetyltransferases; D000199:Actins; D050882:CREB-Binding Protein; D018797:Cell Cycle Proteins; D003402:Creatine Kinase; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004268:DNA-Binding Proteins; D017405:Herpes Simplex Virus Protein Vmw65; D051548:Histone Acetyltransferases; D026161:MADS Domain Proteins; D064326:MEF2 Transcription Factors; D017570:MyoD Protein; D018006:Myogenic Regulatory Factors; D009687:Nuclear Proteins; D012333:RNA, Messenger; D035381:TATA-Binding Protein Associated Factors; D015534:Trans-Activators; D035362:Transcription Factor TFIID; D014157:Transcription Factors; D050880:p300-CBP Transcription Factors; D000099224:p300-CBP-Associated Factor; C493956:CDKN1A protein, human; C493957:Cdkn1a protein, mouse; C578040:MEF2C protein, human; C578041:Mef2c protein, mouse; C494363:CREBBP protein, human; C494364:Crebbp protein, mouse; C069001:TATA-binding protein associated factor 250 kDa