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Basic transcription element binding protein (BTEB) transactivates the cholesterol 7 alpha-hydroxylase gene (CYP7A)
1Department of Biochemistry and Molecular Pathology, Northeastern Ohio Universities College of Medicine, Rootstown 44272, USA.
Biochemical and Biophysical Research Communications
|January 6, 1999
Summary
Researchers identified a protein called basic transcription element binding protein (BTEB) that binds to key DNA regions regulating cholesterol 7 alpha-hydroxylase, an enzyme crucial for bile acid production.
Area of Science:
- Biochemistry
- Molecular Biology
- Genetics
Background:
- Cholesterol 7 alpha-hydroxylase is vital for bile acid synthesis.
- Two bile acid response elements (BARE-I and BARE-II) in the CYP7A gene promoter are critical regulatory regions.
- A conserved sequence (AGTTCAAG) is present in these response elements.
Purpose of the Study:
- To identify nuclear proteins that bind to the bile acid response elements (BAREs) of the cholesterol 7 alpha-hydroxylase gene.
- To elucidate the role of these proteins in regulating CYP7A gene expression.
Main Methods:
- Screening of a human liver cDNA expression library using oligonucleotide probes.
- DNA sequencing and homology searches.
- Electrophoretic mobility shift assays (EMSA).
- Transient transfection assays.
Main Results:
- A clone, G13, was identified and found to be identical to basic transcription element binding protein (BTEB).
- BTEB belongs to the Sp1 family of transcription factors.
- EMSA confirmed BTEB binding to a basic transcription element (BTE) in BARE-II and an Sp1 site in the CYP7A promoter.
- BTEB transactivated the CYP7A promoter in transient transfection assays.
Conclusions:
- Basic transcription element binding protein (BTEB) is a nuclear factor that binds to regulatory regions of the cholesterol 7 alpha-hydroxylase gene.
- BTEB plays a role in the transcriptional regulation of CYP7A, impacting bile acid synthesis.