FIG. 4.

Overexpression of ICER I (A), ICER Iγ (B), ICER II (C), and ICER IIγ (D) attenuates the maximal GnRH transcriptional response of the rFSHβ gene in a dose-dependent manner. LβT2 cells were transfected with 2 μg of −140/+15 rFSHβLuc and increasing amounts of the indicated ICER expression vector, together with 1 μg of a CREB expression vector. Cells were treated 44 h after transfection with 100 nM GnRHAg or vehicle for 4 h prior to harvest. Bar graphs show the luciferase activity (means ± the SEM from triplicate samples, normalized to β-galactosidase activity) from a representative experiment, repeated on three separate occasions with comparable results. Significant differences (P < 0.05), as measured by one-way ANOVA with post hoc Tukey-Kramer multiple-comparison test, are denoted by different letters.