Fig. 4

Conserved residues within the membrane-proximal hinge region of Vpu are important for BST2 counteraction. a A flow cytometry representative overlay showing the amount of surface BST2 following transfections of HeLa cells with either WT Vpu or the indicated Vpu mutants. Mean fluorescence intensity (MFI) values are indicated on the right. b A compilation of four independent experiments showing the extent of surface BST2 downregulation as determined by subtracting BST2 MFI values obtained from transfected cells (GFP+) from those in non-transfected cells (GFP−), and expressed as a percentage relative to the efficiency of BST2 downregulation obtained from WT Vpu, which in turn was arbitrarily set at 100%. c, d Efficiency of virus particle release following transfection of HeLa cells with provirus plasmids encoding WT Vpu and the indicated mutants. c A representative Western blot showing the amount of virion-associated p24 released into the supernatant (virion) and Gag products (p24 and p55) in the cell lysate. d A summary of quantifications of released virus particles by densitometric analyses of the intensity of Gag-related band signals from the Western blots from four different experiments. The efficiency of virus release was determined by calculating the ratio of virion-associated p24 released into the supernatant versus total Gag (cell- and virus-associated), and is expressed as a percentage of the release efficiency of the WT provirus, which in turn was set at 100%. For both (b) and (d), the error bars represent standard deviation (SD). Statistical analyses were performed using a two-way ANOVA, Tukey’s multiple comparison test