title: hMusTRD1alpha1 represses MEF2 activation of the troponin I slow enhancer.
abstract: The novel transcription factor hMusTRD1alpha1 (human muscle TFII-I repeat domain-containing protein 1alpha1; previously named MusTRD1; O'Mahoney, J. V., Guven, K. L., Lin, J., Joya, J. E., Robinson, C. S., Wade, R. P., and Hardeman, E. C. (1998) Mol. Cell. Biol. 18, 6641-6652) was identified in a yeast one-hybrid screen as a protein that binds within an upstream enhancer-containing region of the skeletal muscle-specific gene, TNNI1 (human troponin I slow; hTnIslow). It has been proposed that hMusTRD1alpha1 may play an important role in fiber-specific muscle gene expression by virtue of its ability to bind to an Inr-like element (nucleotides -977 to -960) within the hTnIslow upstream enhancer-containing region that is necessary for slow fiber-specific expression. In this study we demonstrate that both MEF2C, a known regulator of slow fiber-specific genes, and hMusTRD1alpha1 regulate hTnIslow through the Inr-like element. Co-transfection assays in C2C12 cells and Cos-7 cells demonstrate that hMusTRD1alpha1 represses hTnIslow transcription and prevents MEF2C-mediated activation of hTnIslow transcription. Gel shift analysis shows that hMusTRD1alpha1 can abrogate MEF2C binding to its cognate site in the hTnIslow enhancer. Glutathione S-transferase pull-down assays demonstrate that hMusTRD1alpha1 can interact with both MEF2C and the nuclear receptor co-repressor. The data support the role of hMusTRD1alpha1 as a repressor of slow fiber-specific transcription through mechanisms involving direct interactions with MEF2C and the nuclear receptor co-repressor.
authors.affiliation: Muscle Development Unit, Children's Medical Research Institute, Wentworthville, New South Wales 2145, Australia.
authors.forename: Patsie
authors.initials: P
authors.lastname: Polly
authors.forename: Leila M
authors.initials: LM
authors.lastname: Haddadi
authors.forename: Laura L
authors.initials: LL
authors.lastname: Issa
authors.forename: Nanthakumar
authors.initials: N
authors.lastname: Subramaniam
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Palmer
authors.forename: Enoch S E
authors.initials: ES
authors.lastname: Tay
authors.forename: Edna C
authors.initials: EC
authors.lastname: Hardeman
mesh_terms: D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism*; D005786:Gene Expression Regulation; D005982:Glutathione Transferase / Q000378:metabolism; D064326:MEF2 Transcription Factors; D051379:Mice; D008954:Models, Biological; D008957:Models, Genetic; D018657:Muscle Fibers, Slow-Twitch / Q000378:metabolism; D009124:Muscle Proteins; D018482:Muscle, Skeletal / Q000378:metabolism; D018006:Myogenic Regulatory Factors; D009687:Nuclear Proteins; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000737:chemistry* / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015534:Trans-Activators; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D019210:Troponin I / Q000737:chemistry*; D020798:Two-Hybrid System Techniques
chemical_list: D004268:DNA-Binding Proteins; C486558:Gtf2ird1 protein, mouse; D064326:MEF2 Transcription Factors; C578041:Mef2c protein, mouse; D009124:Muscle Proteins; D018006:Myogenic Regulatory Factors; D009687:Nuclear Proteins; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D019210:Troponin I; D004247:DNA; D005982:Glutathione Transferase