Figure 2

M2BP inhibits both HIV-1 Env processing and virion production.

(A–D) An empty vector (−) or increasing amounts of a plasmid expressing M2BP-myc was transfected into HEK293T cells together with the HIV-1-producing plasmids indicated. A plasmid expressing GFP was included to serve as a control for transfection efficiency and sample handling. (A,B) At 48 h posttransfection, p24CA levels in the culture supernatants were measured by ELISA (upper panel). Equal volumes (middle panel) or equal amounts of CA-containing culture supernatants (lower panel) were used to infect HeLa-CD4-CCR5 cells. At 48 h postinfection, luciferase activity was measured in the recipient cells. Relative specific infectivity was defined as the luciferase activity in the recipient cells divided by the amount of the CA-containing virus used to infect the cells. The relative CA protein level, luciferase activity and specific infectivity in the absence of M2BP were set as 100. Data presented are means ± SD of three independent experiments. (C,D) The virions in culture supernatants were pelleted by ultracentrifugation. Protein expressions in the producer cells, culture supernatants and virion pellets were analyzed by Western blotting. Mock: mock transfected cells. (E) The plasmids indicated were transfected into HEK293T cells with (+) or without (−) a plasmid expressing M2BP. A plasmid expressing GFP was included to serve as a control. At 48 h posttransfection, cells and culture supernatants were harvested for Western blotting analyses.