Figure 4

Downregulation of endogenous M2BP enhances HIV-1 virion production.

A control shRNA (Ctrli) or an shRNA targeting M2BP (M2BPi) was stably expressed in HEK293T cells. (A) M2BP protein levels were measured by Western blotting. (B–E) HIV-1-producing plasmids indicated were transiently transfected into cells with (rescue) or without (EV) a rescue M2BP-expressing plasmid. A plasmid expressing GFP was included to serve as a control for transfection efficiency and sample handling. (B,C) At 48 h posttransfection, equal volumes of culture supernatants were used to infect HeLa-CD4-CCR5 cells. At 48 h postinfection, luciferase activity was measured. The relative luciferase activity in the cells infected with the virus produced in control cells was set as 100. Data presented are means ± SD of three independent experiments. (D,E) The producer cells and culture supernatants were harvested for Western blotting analyses. The intensities of the p24CA bands in culture supernatants and the p55Gag bands in cell lysates were quantified with the Image J software. The p24CA release level was calculated as the p24CA level in the culture supernatant divided by the p55Gag level in the cell lysate. The relative p24CA release level in the absence of M2BP was set as 100. Data presented are means ± SD of three independent experiments. **p < 0.01