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Functional difference between Ad4BP and ELP, and their distributions in steroidogenic tissues
K Morohashi1, H Iida, M Nomura
1Department of Molecular Biology, Graduate School of Medical Science, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Molecular Endocrinology (Baltimore, Md.)
|May 1, 1994
Summary
Ad4BP, a transcription factor, is expressed in steroidogenic tissues like the adrenal gland, ovary, and testis. While ELP, a related protein, recognizes the same DNA sequences, Ad4BP exhibits stronger binding and transcriptional activation.
Area of Science:
- Molecular Endocrinology
- Steroidogenesis Regulation
- Transcription Factor Function
Background:
- Ad4BP (Adrenal-4 binding protein) is a zinc finger DNA-binding protein involved in regulating steroidogenic P-450 genes.
- cAMP-dependent regulation of steroidogenesis is crucial for adrenal, ovarian, and testicular functions.
- ELP (Embryonic Leucine-rich Protein) is a mammalian counterpart of Drosophila FTZ-F1, sharing similar DNA recognition sequences with Ad4BP.
Purpose of the Study:
- To investigate the expression and function of Ad4BP in steroidogenic tissues.
- To compare the transcriptional activity and DNA-binding affinity of Ad4BP and its isoform ELP.
- To elucidate the role of Ad4BP in the regulation of CYP11B gene expression.
Main Methods:
- Immunochemical and immunohistochemical analyses using antiserum to Ad4BP in adrenal, ovarian, and testicular tissues.
- Immunoblotting of corpora lutea to assess Ad4BP and side-chain cleavage P-450 expression.
- Reverse transcriptase-polymerase chain reaction (RT-PCR) to detect ELP expression in steroidogenic tissues.
- Transient transfection assays with expression vectors for Ad4BP and ELP to study CYP11B gene transcription.
- Gel shift analysis to compare the DNA-binding activity of Ad4BP and ELP.
Main Results:
- Ad4BP expression was confirmed in all three zones of the adrenal cortex, ovarian follicle (granulosa and thecal cells), corpus luteum, and Leydig cells of the testis.
- Ad4BP and side-chain cleavage P-450 expression levels were parallel in corpora lutea, decreasing in regressed tissues.
- Steroidogenic tissues express both Ad4BP and ELP.
- ELP did not activate CYP11B gene transcription and weakly inhibited Ad4BP-mediated transactivation.
- In vitro synthesized ELP exhibited significantly weaker DNA-binding activity compared to Ad4BP.
Conclusions:
- Ad4BP is widely expressed in mammalian steroidogenic tissues, suggesting a broad role in regulating steroidogenic genes.
- Despite recognizing similar DNA sequences, Ad4BP is a more potent transcriptional activator of the CYP11B gene than ELP.
- The differential DNA-binding affinities and transcriptional activities of Ad4BP and ELP may contribute to the precise regulation of steroidogenesis.