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The muscle creatine kinase gene is regulated by multiple upstream elements, including a muscle-specific enhancer
J B Jaynes1, J E Johnson, J N Buskin
1Department of Biochemistry, University of Washington, Seattle 98195.
Molecular and Cellular Biology
|January 1, 1988
Summary
Researchers identified a key enhancer element in the mouse muscle creatine kinase (MCK) gene, crucial for its high expression during skeletal muscle differentiation. This enhancer controls tissue-specific gene activation in myoblasts.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Muscle creatine kinase (MCK) expression is significantly upregulated during skeletal muscle differentiation.
- Understanding the regulatory mechanisms controlling MCK gene activation is vital for comprehending myogenesis.
Purpose of the Study:
- To identify and characterize the upstream regulatory elements responsible for MCK gene activation during muscle differentiation.
- To investigate the role of these elements in conferring tissue and differentiation specificity to MCK expression.
Main Methods:
- Transfection of fusion genes containing mouse MCK 5' flanking DNA and the chloramphenicol acetyltransferase (CAT) gene into cultured myoblasts and nonmyogenic cells.
- Comparison of CAT expression in proliferating versus differentiated myoblasts and in myoblasts versus nonmyogenic cells.
- Sequence analysis and comparison of the identified MCK enhancer with known viral and cellular enhancer elements.
Main Results:
- A potent transcriptional enhancer element was identified between 1,050 and 1,256 nucleotides upstream of the MCK transcription start site.
- This enhancer significantly increased MCK gene expression specifically in differentiated muscle cells, demonstrating tissue and differentiation specificity.
- Sequence comparisons revealed similarities between the MCK enhancer and regulatory regions of simian virus 40 and immunoglobulin heavy-chain enhancers.
- Even without the enhancer, the MCK promoter retained some differentiation-specific activity, suggesting the presence of other regulatory elements.
- Evidence for negative regulatory elements acting in myoblasts was also observed.
Conclusions:
- The identified enhancer is a major determinant of high-level MCK expression and tissue-specific activation during myogenesis.
- The MCK enhancer shares features with other known enhancers, suggesting conserved mechanisms for gene regulation.
- Both positive (enhancer) and potentially negative regulatory elements contribute to the precise control of MCK gene expression in a cell type- and differentiation-dependent manner.