Figure 4.

Overexpression of YY1 selectively represses the vitamin D induction of OC promoter activity. Vitamin D induction of a panel of CAT reporter gene constructs (see Fig. 1) was determined in the absence or presence of different amounts of pCMV-YY1 expression plasmid. ROS 17/2.8 cells were transfected by p1097 OC-CAT or p348 OC-CAT reporter gene construct (Left). The OP promoter CAT constructs p772 OP-CAT and p552 OP-CAT (Fig. 1A) were used as reporter for similar transfection assays (Right). (B) Cotransfection experiments were performed as described in A using the p1097 OC(mtC)-CAT construct, which contains a YY1-specific mutation (mtC) in the OC-VDRE sequences. (C) Results of cotransfection experiments with ROS 17/2.8 using a reporter gene construct containing four copies of the OC-VDRE fused to a heterologous promoter [(VDRE)4L^d-LUC] and the YY1 expression plasmid (pCMV-YY1; amounts indicated below the graph). All values are relative to the control in the absence of vitamin D and pCMV-YY1. Fold inductions were calculated by dividing promoter activity (in relative luciferase units) in the presence of vitamin D (10⁻⁸ M) by promoter activity in the absence of vitamin D control.