A novel myogenic regulatory circuit controls slow/cardiac troponin C gene transcription in skeletal muscle
| Autor: | Hon S. Ip, James F. Martin, Eric N. Olson, Jeffrey M. Leiden, Frank Jung, Tingliang Shen, Anuradha J. Vora, Michael S. Parmacek |
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| Rok vydání: | 1994 |
| Předmět: |
Transcriptional Activation
Transcription Genetic Macromolecular Substances Molecular Sequence Data Biology MyoD Cell Line Mice MyoD Protein Sequence Homology Nucleic Acid Consensus Sequence Animals Myocyte Amino Acid Sequence RNA Messenger Enhancer Molecular Biology Transcription factor Myogenin Regulation of gene expression Binding Sites Base Sequence Sequence Homology Amino Acid Myogenesis Muscles Helix-Loop-Helix Motifs Nuclear Proteins Cell Biology musculoskeletal system Molecular biology Introns Troponin DNA-Binding Proteins Enhancer Elements Genetic Gene Expression Regulation Oligodeoxyribonucleotides Troponin C Sequence Alignment Research Article |
| Zdroj: | Molecular and Cellular Biology. 14:1870-1885 |
| ISSN: | 1098-5549 0270-7306 |
| Popis: | The slow/cardiac troponin C (cTnC) gene is expressed in three distinct striated muscle lineages: cardiac myocytes, embryonic fast skeletal myotubes, and adult slow skeletal myocytes. We have reported previously that cTnC gene expression in cardiac muscle is regulated by a cardiac-specific promoter/enhancer located in the 5' flanking region of the gene (bp -124 to +1). In this report, we demonstrate that the cTnC gene contains a second distinct and independent transcriptional enhancer which is located in the first intron. This second enhancer is skeletal myotube specific and is developmentally up-regulated during the differentiation of myoblasts to myotubes. This enhancer contains three functionally important nuclear protein binding sites: a CACCC box, a MEF-2 binding site, and a previously undescribed nuclear protein binding site, designated MEF-3, which is also present in a large number of skeletal muscle-specific transcriptional enhancers. Unlike most skeletal muscle-specific transcriptional regulatory elements, the cTnC enhancer does not contain a consensus binding site (CANNTG) for the basic helix-loop-helix (bHLH) family of transcription factors and does not directly bind MyoD-E12 protein complexes. Despite these findings, the cTnC enhancer can be transactivated by overexpression of the myogenic bHLH proteins, MyoD and myogenin, in C3H10T1/2 (10T1/2) cells. Electrophoretic mobility shift assays demonstrated changes in the patterns of MEF-2, CACCC, and MEF-3 DNA binding activities following the conversion of 10T1/2 cells into myoblasts and myotubes by stable transfection with a MyoD expression vector. In particular, MEF-2 binding activity was up-regulated in 10T1/2 cells stably transfected with a MyoD expression vector only after these cells fused and differentiated into skeletal myotubes. Taken together, these results demonstrated that distinct lineage-specific transcriptional regulatory elements control the expression of a single myofibrillar protein gene in fast skeletal and cardiac muscle. In addition, they show that bHLH transcription factors can indirectly transactivate the expression of some muscle-specific genes. |
| Databáze: | OpenAIRE |
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