Figure 6. p21 represses the activity of human CCNE2 promoter.

A. K562 cells were transfected with luciferase reporters carrying the promoters cyclin E1 and E2 genes (CCNE1 and CCNE2), along with an expression vector for p21 and the corresponding empty vector, and a beta-gal plasmid for transfection efficiency normalization. 24 h after transfection the luciferase activities were determined. The data are normalized to the activity of cells transfected with the empty vector. Lower panel: immunoblot analysis of the transfected cells to assess the expression of p21. B. Kp21-4 cells were transfected with luciferase reporters carrying the promoters cyclin E1 and E2 genes as in (A) and 24 h later the cells were treated with 75 µM ZnSO₄ and after 24 h the luciferase activities were determined. The data are normalized to the activity of cells without ZnSO₄. Lower panel: immunoblot analysis of the transfected cells to assess the expression of p21.