Figure 4.

E2F1 induction of p57^KIP2 is p73-dependent. (a) Saos-E2F1 and Saos-E2F1-DDp73 cells were untreated (−) or treated (+) with 2 μg/ml doxycycline (Dox) for 12 h, and total RNA was analyzed by RNase protection. Protected probes specific for p57^KIP2 and GAPDH are shown. (b) Saos-E2F1 and Saos-E2F1-DDp73 cells were untreated (0) or treated with doxycycline for the indicated times (hours Dox). Expression of E2F1, DDp73, and p57^KIP2 proteins was analyzed by Western blotting. Actin expression was examined as a loading control. (c) Primary human retinal pigment epithelial cells without (−) or with (+) E1A were examined for p73β and p57^KIP2 mRNA expression levels by RT-PCR. GAPDH expression was included as a loading control.