p21 represses the activity of human CCNE2 promoter.

<p>A. K562 cells were transfected with luciferase reporters carrying the promoters cyclin E1 and E2 genes (<i>CCNE1</i> and <i>CCNE2</i>), 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.