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Human calcitonin gene regulation by helix-loop-helix recognition sequences
D W Ball1, D Compton, B D Nelkin
1Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21231.
Nucleic Acids Research
|January 11, 1992
Summary
Helix-loop-helix (HLH) proteins regulate human calcitonin (CT) gene transcription. Specific HLH recognition motifs in the CT gene enhancer are crucial for basal activity in neuroendocrine tumor cells.
Area of Science:
- Molecular Biology
- Genetics
- Cancer Biology
Background:
- Human calcitonin (CT) gene expression is controlled by regulatory DNA sequences.
- Proximal sequences mediate cAMP-induced expression, while a distal enhancer governs basal activity.
Purpose of the Study:
- To investigate the role of the distal basal enhancer region in human calcitonin (CT) gene transcription.
- To identify specific DNA elements and protein factors involved in regulating CT gene expression in tumor cells.
Main Methods:
- Transient expression assays using CT-CAT constructs.
- Deletional and mutational analyses of the distal enhancer region.
- Electrophoretic mobility shift assays (EMSAs) to detect protein-DNA interactions.
Main Results:
- The distal enhancer is active in CT-producing cell lines (DMS53, TT) but not in non-CT-producing lines.
- Disruption of two helix-loop-helix (HLH) recognition motifs significantly reduced enhancer activity.
- Nuclear proteins from DMS53 cells specifically bound to oligonucleotides containing these HLH motifs.
Conclusions:
- Helix-loop-helix (HLH) recognition motifs are critical for basal human calcitonin (CT) gene transcription.
- HLH proteins, potentially a combination of ubiquitous and tissue-restricted forms, enhance CT gene transcription in neuroendocrine tumor cells.