FIG. 1.

Loss of p53 function is sufficient for Ras induced proliferation in the absence of mitogens. (A) Phase-contrast images of pools of Schwann cells expressing either a dominant-negative mutant of p53 (dnp53) or the SV40 LT, together with HRasVal12 (Ras) or the empty retroviral vector LXSN. (B) Asynchronous populations of Schwann cells were cultured in normal culture medium or defined medium containing no mitogen for 40 h. The percentage of cells entering S phase was determined by measuring BrdU incorporation 12 h prior to fixing and staining. The error bars indicate the standard deviations of triplicate assays.