Transcriptional regulation of the human FTZ-F1 gene encoding Ad4BP/SF-1.
Ad4BP, also known as SF-1, is a steroidogenic tissue-specific transcription factor that is also essential for adrenal and gonadal development. Two mechanisms for the transcriptional regulation of the mammalian FTZ-F1 gene encoding Ad4BP in adrenocortical cells have been proposed in the previous studies: the crucial role of a cis-element, an E box for the steroidogenic cell-specific expression of mouse and rat FTZ-F1 genes, and a possible autoregulatory mechanism of the rFTZ-F1 gene by Ad4BP itself through binding to the Ad4 (or SF-1) site in the first intron. In the present study, the transcriptional regulation of the human FTZ-F1 gene in adrenocortical cells was investigated from several angles, including the above two mechanisms. Using a series of deletion analyses of the 5'-flanking region of the hFTZ-F1 gene and site-directed mutagenesis for transient transfection studies, an E box element, CACGTG at -87/-82 from the transcriptional start site, was also found to be essential for the transcription of the hFTZ-F1 gene in mouse or human adrenocortical cell lines as well as in non-steroidogenic CV-1 cells. Despite the presence of a corresponding Ad4 site, CCAAGGCC at +163/+156 in the first intron of the hFTZ-F1 gene, an autoregulatory mechanism through the Ad4 site was found to be unlikely in the hFTZ-F1 gene mainly due to site-directed mutagenesis. In addition, the forced expression of Ad4BP had little effect on hFTZ-F1 gene transcription in non-steroidogenic CV-1 cells. Such Ad4BP-independent regulation of the hFTZ-F1 gene was in striking contrast to the regulation of steroidogenic CYP genes, such as the human CYP11A gene, in which the proximal promoter activity is Ad4BP-dependent and the transactivation by Ad4BP is silenced by DAX-1. Even though the Ad4BP-dependent transcriptional regulation of the DAX-1 gene has been reported, DAX-1 did not affect the transcriptional activity of the hFTZ-F1 gene in our study. Taken together, these observations suggest that the E box is indeed required for the expression of the FTZ-F1 gene, at least in mammalian species, but may not determine the tissue-specific expression of the hFTZ-F1 gene, and that, unlike the steroidogenic CYP gene, the regulation of the hFTZ-F1 gene appears to be independent of both Ad4BP and DAX-1.
Oba
K
K
The Third Department of Internal Medicine, Faculty of Medicine, Kyushu University, Maidashi Higashi-ku, Fukuoka 812-8582, Japan.
Yanase
T
T
Ichino
I
I
Goto
K
K
Takayanagi
R
R
Nawata
H
H
D000302:Adrenal Cortex / Q000378:metabolism*; D000818:Animals; D001483:Base Sequence; D002417:Cattle; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D057137:DAX-1 Orphan Nuclear Receptor; D017931:DNA Primers / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D004587:Electrophoresis, Agar Gel; D051717:Fushi Tarazu Transcription Factors; D005786:Gene Expression Regulation / Q000235:genetics; D005822:Genetic Vectors; D000882:Haplorhini; D018398:Homeodomain Proteins; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D018160:Receptors, Cytoplasmic and Nuclear; D018168:Receptors, Retinoic Acid / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid; D012097:Repressor Proteins; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012689:Sequence Homology, Nucleic Acid; D054339:Steroidogenic Factor 1; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000378:metabolism
D057137:DAX-1 Orphan Nuclear Receptor; D017931:DNA Primers; D004268:DNA-Binding Proteins; D051717:Fushi Tarazu Transcription Factors; D018398:Homeodomain Proteins; C539965:NR0B1 protein, human; C539966:Nr0b1 protein, mouse; C539967:Nr0b1 protein, rat; D018160:Receptors, Cytoplasmic and Nuclear; D018168:Receptors, Retinoic Acid; D012097:Repressor Proteins; D054339:Steroidogenic Factor 1; D014157:Transcription Factors; D008156:Luciferases; D015500:Chloramphenicol O-Acetyltransferase