INDUCTIONS OF IMMEDIATE-EARLY GENES (IEGS) AND REF-1 BY HUMAN CHORIONIC-GONADOTROPIN IN MURINE LEYDIG-CELL LINE (MA-10)

The effect of human chorionic gonadotropin (hCG) on the expression of immediate early genes (IEGs) including all members of fos and jun fami ly, and c-myc was studied using mouse Leydig cell line (MA-10 cells) b y Northern blot analyses. In addition, the induction of ref-1 which en hances DNA binding of fos/jun proteins was also analyzed. HCG induced a rapid and transient expression of c-fos, fosB, c-jun, junB, junD and c-myc with a peak at 30 min to 1h. In contrast, induction of fra-1 mR NA was delayed with a peak at 3 hr. However, fra-2 mRNA was immediatel y increased by hCG with a peak at 1 h. The ref-1 mRNA was expressed be fore the stimulation and its level was not altered by hCG at least for 8 hr. The differential induction of IEGs and continuous expression of ref-1 mRNA suggest an important role of their gene products on the re gulation of Leydig cell function by hCG.