FUNCTIONAL DIFFERENCE BETWEEN AD4BP AND ELP, AND THEIR DISTRIBUTIONS IN STEROIDOGENIC TISSUES

Ad4BP, a zinc finger DNA-binding protein, was identified as a transcri ption factor regulating steroidogenic P-450 genes in a cAMP-dependent manner. Immunochemical and immunohistochemical studies with steroidoge nic tissues, adrenal, ovary, and testis, were performed using the anti serum to Ad4BP. Ad4BP was expressed to the same extent in the three zo nes of the adrenal cortex. Immunohistochemical examination of ovarian follicle and corpus luteum showed the expression of Ad4BP. The granulo sa and thecal cells, the two distinct types of the steroidogenic cells in the follicle, gave Ad4BP signals, which were stronger than in the latter cells than in the former. Immunoblot analyses of mature and reg ressed corpora lutea indicated a parallel expression of Ad4BP and side -chain cleavage P-450, and both proteins significantly decreased in th e regressed tissues. Leydig cells surrounding seminiferous tubules gav e clear immunostaining signals for Ad4BP. ELF, a mammalian counterpart of Drosophila FTZ-F1 detected in EC cells, and are isoforms transcrib ed from the same gene. The Ad4BP and ELF forms recognize same nucleoti de sequences. Reverse transcriptase-polymerase chain reaction with spe cific primers for ELF revealed that steroidogenic tissues contained EL F as well as Ad4BP. The effects of the two proteins on the transcripti on of the CYP11B gene were compared using the expression vectors of Ad 4BP and ELF. ELF did not activate transcription and showed a weak inhi bitory effect on the Ad4BP-dependent transactivation of the CYP11B gen e promoter when transfected simultaneously. A gel shift analysis using in vitro synthesized Ad4BP and ELF revealed that the binding activity of ELF is significantly weaker than that of Ad4BP.