Abstract
The orphan nuclear receptor, steroidogenic factor 1 (SF-1), plays a major role in adrenal andgonadal development, as well as in sexual differentiation. It has been demonstrated that the expressionof a number of genes regulated by SF-1 is inhibited by the transforming growth factor β (TGF-β). Todate, however, the influence of TGF-β on the expression of SF-1 gene has not been reported. A Northernblot analysis with the use of a radiolabeled cDNA probe, and immunodetection with antibodiesdirected against SF-1, demonstrated that the Sf-1 transcript and the SF-1 protein levels were loweredby TGF-β in Y-1 adrenocortical cells, both in untreated and adenylyl cyclase activator, forskolintreatedcells. An examination of the Sf-1 transcript stability in the presence of actinomycin Drevealed no influence of TGF-β on the rate of Sf-1 mRNA decay. Inhibition of Sf-1 expression byTGF-β was abolished by cycloheximide, suggesting that the growth factor inhibitory effect requiresongoing protein synthesis. We conclude that in Y-1 cells TGF-β inhibits the expression of SF-1 geneat a transcriptional level, and we postulate that the inhibitory effect of TGF-β on steroid hormonesynthesis in the adrenal cortex could be due to an attenuated transcription of Sf-1.
Published Version
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