Figure 2.

Growth regulation byp37^Ing1. A, proliferation of p37^Ing1-deficient cells. Two independent MEF cell lines of p37^Ing1-Wt, p37^Ing1-heterozygous, p37^Ing1-null, or p53-null genotypes were plated in triplicate in 60-mm plates and growth was analyzed over the course of 7 d. Statistical analysis between Wt and p37^Ing1-heterozygous curves shows no significant difference (P < 1.00), but there is statistical difference between Wt and p37^Ing1-null curves (P < 0.005). B, growth of p37^Ing1-deficient cells at low density. Two lines of Wt, p37^Ing1-heterozygous, or p37^Ing1-homozygous genotype were seeded at 10⁴ cells per 10-cm plate and incubated for 8 to 12 d before staining with crystal violet. C, growth inhibition by p37^Ing1 is independent of p53 status. Three MEF cell lines deficient for p53 or for p53 and p37^Ing1 were plated in triplicate in six-well plates and counted over a 7-d period. Wild-type MEFs were also similarly plated as a control. A statistical difference exists between the proliferation rates of p53-null and p37^Ing1/p53-double null MEFs (P < 0.0005). D, immortalization of p37^Ing1-deficient cells. A 3T9 assay was done using two independent MEF cell lines of p37^Ing1-Wt, p37^Ing1-null, or p53-null MEFs.