The functional effect of Vpu expression on p53-mediated apoptosis. (A) H-1299 (p53 null) cells were cotransfected with plasmids encoding p53 and either Vpu B, Vpu C, or M Vpu-HA. Then after 72 hours, cells were harvested, fixed, and stained with PI, and subG₁ DNA content was determined by FACS to see relative proportion of apoptotic population that is summarized below the histograms. (B.) H-1299 cells were cotransfected with p53wt and Vpu B, Vpu C, or M Vpu-HA, and endogenous Bax levels were checked by immunoblotting analysis with the indicated Abs. (C.) H-1299 cells were cotransfected with indicated plasmids, and cell lysates were subjected to immunoblot analysis. This is a representative result obtained from 3 independent experiments.