Knockdown of p53 protects cells against BFA-induced cell death.

<p>Down-regulation of p53 expression by p53 RNAi during ER stress. (A) MCF-7 cells were cotransfect with pcDNA3.1/pSuper or pcDNA3.1/pSuper-p53 RNAi plasmid by Lipofectammine 2000. The stable transfectants were selected by G418, and then expression of p53 was analyzed by immunoblotting (upper panel). The cell growth rate of MCF-7, MCF-7-pSuper, MCF-7-pSuper-p53-1, and MCF-7-pSuper-p53-2 cells were performed by MTT assay (lower panel). Furthermore, western blot analyses of the expression levels of p53 in MCF-7 cells were subjected to tunicamycin treatment (lower panel). (B) The morphologic changes after a 48-hour 2.5 µg/ml and 5 µg/ml tunicamycin treatment of MCF-7 cells. The cells were followed by photography under phase-contrast magnification. (C) shRNA-mediated knockdown of p53 protects MCF-7 cells from Tunicamycin- or Brefeldin A-induced cell death. The stable transfectants were incubated with Tunicamycin or Brefeldin A in 10% FBS–supplemented DMEM for 48 hr. Cell viability was measured by the MTT assay. <i>Columns,</i> mean of three independent experiments; bars, SD (*, <i>P</i><0.05; **, <i>P</i><0.01, Student's t test).