Fig. 6. Increased p21 protein levels in Rad51-overexpressing cells. (A) Immunoblot analysis of human wild-type PPL and Rad51-overexpressing PPL928.1-2 cells. Total cell extracts were prepared from untreated and etoposide (etop.)-treated cultures. Equal amounts of total cellular protein were loaded and analyzed by western blotting with antibodies for p21, ß-actin (loading control) and p53. p21 protein expression was calculated from three independent western blot experiments. The amount of p21 in untreated wild-type cells was chosen as a reference (100%). (B) Relative mRNA expression of selected genes in PPL928.1-2 versus PPL cells. The fluorescence ratios of three ESTs for each gene were measured in three independent chip hybridization experiments. p21 and c-Abl showed an approximately twofold increase in Rad51-overexpressing PPL928.1-2 cells. (As total RNA was reverse transcribed from oligo(dT) primers, the transfected Rad51 mRNA levels could not be determined.)