Figure 6.

Identification of a DNA hairpin structure in the mouse StAR promoter and the effect of DAX-1 on PKA- and PKC-mediated StAR promoter activity. A, Presence of a putative DAX-1 binding motif in the mouse StAR gene. This motif is located between −44 and −20 bp and is composed of five nucleotides stem and 15 nucleotides loop. B, MA-10 cells were transfected with different StAR reporter plasmids (−151/−1 and −68/−1 bp) in the presence of 20 ng of pRL-SV40 vector (renilla luciferase for determining transfection efficiency). Schematic representations of different StAR reporters (−151 and −68 bp) are shown (bottom panel). pGL3 basic (pGL3) was used as a control. Cells were also transfected with empty vector (pcDNA3) or DAX-1 expression plasmid, within the context of the −151/−1 wild-type and mutant StAR reporter segments as indicated, in the presence of pRL-SV40 (C). After 36 h of transfection, cells were incubated for a further 6 h in the absence (basal) or presence of either (Bu)₂cAMP (0.5 mm) or PMA (10 nm), and luciferase activity in the cell lysates was determined and expressed as relative light units (RLU, luciferase/renilla). Relative fold activity is illustrated above bar diagrams. Data represent the mean ± se of four independent experiments. Letters above the bars indicate that these groups differ significantly from each other at least at P < 0.05.