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Regulatory elements governing transcription in specialized myofiber subtypes
Z Yan1, A L Serrano, S Schiaffino
1Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
The Journal of Biological Chemistry
|March 30, 2001
Summary
Researchers identified key DNA regions controlling myoglobin gene expression in muscle fibers. A novel intragenic E-box motif acts as a negative regulator, explaining variations in myoglobin levels across different muscle fiber types.
Area of Science:
- Molecular Biology
- Muscle Physiology
- Genetics
Background:
- Skeletal muscle fibers exhibit diverse metabolic and physiological characteristics.
- Myoglobin gene expression is tightly regulated, correlating with oxidative versus glycolytic fiber types.
- Oxidative myofibers (Types I and IIa) show high myoglobin, while glycolytic fibers (Type IIb) have lower levels.
Purpose of the Study:
- To identify regulatory DNA regions responsible for muscle- and fiber type-specific myoglobin expression.
- To investigate the role of specific DNA motifs in myoglobin gene regulation.
- To uncover novel regulatory elements influencing myoglobin expression variability.
Main Methods:
- Germ-line transgenesis in mice.
- Somatic cell gene transfer.
- Mutational analysis of murine and human myoglobin genes.
- Reporter gene assays.
Main Results:
- Defined discrete gene regions sufficient for muscle- and fiber type-specific expression.
- Confirmed the importance of A/T-rich, MEF2-binding motifs in regulation.
- Identified an intragenic E-box motif functioning as a negative regulatory element.
Conclusions:
- Specific DNA sequences govern myoglobin expression in different muscle fiber types.
- MEF2-binding sites are crucial for positive regulation of myoglobin.
- An intragenic E-box acts as a novel negative regulator, contributing to fiber-type-specific expression patterns.