Fig. 7. Expression of the cell cycle regulator p21 in response to expression of wild-type p53. Mock-transfected and p53-expressing K562 clones were incubated at 32°C (i.e., the temperature permissive for the wild-type conformation of p53) for 22 h, after which the cells were subjected to Western blot, as described in "Materials and Methods." Arrow to the right, position of p21 protein at Mr 21,000. Left, positions of molecular weight standards.