Figure 1 - Mitogenic signals cooperate with pRb and/or p53 to induce irreversible cell-cycle arrest.

(a) Time line of temperature shift experiments using SVts8 cells. SVts8 cells were cultured in normal serum (10%) medium at 34 °C. Cells were then incubated at 38.5 °C in normal serum medium or in low serum (0.2%) medium for 5 days. These cells were subsequently incubated at 34 °C in normal serum medium for another 5 days. Representative photographs of the cells in the indicated culture conditions are shown. The scale bars represent 200 m. (b) Total cell lysates were prepared at indicated times in a (clumn number corresponds to culture condition in Fig. 1a) and were immunoblotted (IB) after immunoprecipitation (IP). The antibodies used are indicated. The total amount of Cdc2, p21 and -actin were monitored by direct immunoblotting of the cell lysate. (c) A BrdU incorporation assay was performed at the times indicated in a. The means s.d. of three independent experiments are shown. (d) SVts8 cells were cultured at 38.5 °C either in normal serum medium (4) or in low serum medium (5) for 5 days. Cells were then cultured at 34 °C in normal serum medium and were subjected to a cell proliferation assay performed in triplicate. The means s.d. of three independent experiments are shown.