FIG. 5.
v-Fos does not alter the p53 response to DNA damage. (A) Comparison of the expression levels of p53 and p21 in telomerase-immortalized fibroblasts after DNA damage induced by etoposide. Cells were treated with 1 μM etoposide and lysed at the indicated times for Western blot analysis of p53 and p21Cip1/Waf1. p53 was inactivated in Tif cells with HPV16 E6 or mutant p53 (mtp53). The membranes were stripped and reprobed for ERK2 as a loading control. (B) Flow cytometric analysis of the cell cycle phase distribution after DNA damage induced by etoposide in telomerase-immortalized fibroblasts. Exponentially growing cells were incubated in the absence or presence of 1 μM etoposide for 20 h, stained with propidium iodide for DNA content, and analyzed by flow cytometry. The DNA content histograms are shown along with the distribution of cells in the G1, S and G2/M phases of the cell cycle.