FIG. 2.

Rac1, RhoA, and Cdc42 contribute to the growth regulation of p19Arf- or p53-null cells. The dominant negative mutants of Rho proteins were expressed in the Arf^−/− or p53^−/− MEFs by retroviral induction, and the Rho mutant-expressing cells were isolated by FACS. (A) Five thousand cells/well of the indicated cells were plated in 1-ml culture medium containing 5% fetal bovine serum on 24-well plates. At the time points of day 0, 1, 2, 3, and 4, incorporation of [³H]thymidine into the cells was measured. Data are representative of three independent experiments and are expressed as the fold of growth relative to the respective value at day 0. Error bars represent the standard deviations of four repeats of one experiment. (B) Western blots of the endogenous Rac1, RhoA, and Cdc42 in the GTP-bound state were performed after the respective GST-effector domain pull-downs in the wild-type (WT) MEFs, p53-deficient MEFs, and p53-deficient MEFs expressing various dominant negative mutants of Rh proteins. The amounts of each Rho protein in the respective cell lysates and in the GTP-bound form were normalized to that of Rac1, RhoA, or Cdc42 in WT MEFs.