The orphan nuclear receptor, COUP-TF II, inhibits myogenesis by post-transcriptional regulation of MyoD function: COUP-TF II directly interacts with p300 and myoD.
COUP-TF II is an orphan nuclear receptor that has no known ligand in the 'classical sense'. COUP-TF interacts with the corepressors N-CoR, SMRT and RIP13, and silences transcription by active repression and trans-repression. Forced expression of the orphan nuclear receptor COUP-TF II in mouse C2 myogenic cells has been demonstrated to inhibit morphological differentiation, and to repress the expression of: (i) the myoD gene family which encodes myogenic basic helix-loop-helix (bHLH) proteins; and (ii) the cell cycle regulator, p21(Waf-1/Cip-1). In the present study, we show that COUP-TF II efficiently inhibits the myoD -mediated myogenic conversion of pluripotential C3H10T1/2 cells by post-transcriptional mechanisms. Furthermore, repression of MyoD-dependent transcription by COUP-TF II occurs in the absence of the nuclear receptor cognate binding motif. The inhibition of MyoD-mediated trans-activation involves the direct binding of the DNA binding domain/C-region and hinge/D-regions [i.e. amino acid (aa) residues 78-213] of COUP-TF II to the N-terminal activation domain of MyoD. Over-expression of the cofactor p300, which functions as a coactivator of myoD-mediated transcription, alleviated repression by COUP-TF II. Further binding analysis demonstrated that COUP-TF II interacted with the N-terminal 149 aa residues of p300 which encoded the receptor interaction domain of the coactivator. Finally we observed that COUP-TF II, MyoD and p300 interact in a competitive manner, and that increasing amounts of COUP-TF II have the ability to reduce the interaction between myoD and p300 invitro. The experiments presented herein suggest thatCOUP-TF II post-transcriptionally regulates myoD activity/function, and that crosstalk between orphan nuclear receptors and the myogenic bHLH proteins has functional consequences for differentiation.
Bailey
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P
University of Queensland, Centre for Molecular and Cellular Biology, Ritchie Research Laboratories, B402A, St Lucia, 4072 Queensland, Australia.
Sartorelli
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V
Hamamori
Y
Y
Muscat
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GE
D016475:3T3 Cells; D000818:Animals; D001667:Binding, Competitive / Q000235:genetics; D051836:COUP Transcription Factors; D002454:Cell Differentiation / Q000235:genetics; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000502:physiology*; D050881:E1A-Associated p300 Protein; D018507:Gene Expression Regulation, Developmental; D017930:Genes, Reporter; D006801:Humans; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D018482:Muscle, Skeletal / Q000166:cytology* / Q000378:metabolism*; D017570:MyoD Protein / Q000378:metabolism* / Q000502:physiology; D009687:Nuclear Proteins / Q000502:physiology*; D010446:Peptide Fragments / Q000502:physiology; D012323:RNA Processing, Post-Transcriptional; D011987:Receptors, Steroid; D012097:Repressor Proteins / Q000502:physiology*; D015534:Trans-Activators / Q000502:physiology*; D014157:Transcription Factors / Q000502:physiology*; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured
D051836:COUP Transcription Factors; D004268:DNA-Binding Proteins; D017570:MyoD Protein; D009687:Nuclear Proteins; D010446:Peptide Fragments; D011987:Receptors, Steroid; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D050881:E1A-Associated p300 Protein; C494361:Ep300 protein, mouse