Kinetics of p21WAF1/CIP1, Mdm2, and p53 reporter activity in tsBN462 and BHK21 cells at the nonpermissive temperature. tsBN462 and BHK21 cells were transfected in six-well dishes with either the WAF1-luc (A), pCON-luc, pGUP-luc, pG13-luc, and mG15-luc (B), or Mdm2-luc (C) reporters (1 μg) and the internal control (pSG5-LacZ; 1 μg/ml). After transfection, the cells were transferred to 39°C, and luciferase activities were measured at various times. Luciferase activities at any particular time point were corrected for variations in transfection efficiency using the internal control. Fold activation (B) is the ratio of the activities of the reporters containing (pCON-luc and pG13-luc) and lacking (pGUP-luc and mG15-luc) functional p53 response elements. Similar results were obtained in three separate experiments.