FIGURE 3.

p53 is a determinant of Hsp90 ATPase activity. A–C, cells were transfected with 2 μg of p53 siRNA or GFP (control) siRNA for 48 h. Cells were then harvested. D, EB-1 cells were treated with the indicated concentrations of ZnCl₂ for 12 h prior to being harvested. E and F, cells were treated with CP-31398 as indicated for 24 h before being harvested. A–F, cell lysates were used to measure Hsp90 ATPase activity using the method described under “Experimental Procedures.” Mean ± S.D. (error bars) are shown, n = 6. *, p < 0.01 compared with control siRNA-treated cells (A–C) or vehicle-treated cells (D–F). Cell lysates were also subjected to Western blotting, and the blots were probed as indicated in the insets.