Fig. 4.
Inhibition of HIV-1 release and infectivity by BST2 proteins. (A) Western blot of samples from 293 T cells that expressed HIV-1ΔVpu and either lacked BST2 (lane 1, unrestricted control) or expressed increasing levels of wild-type BST2 (lanes 2–6) or BST2(L70D) (lanes 7–11). Panel 1, levels of virion-associated viral Gag proteins released into the supernatant (VIRUS, anti-CA and anti-MA). Panel 2, intracellular Gag protein levels (CELLS, anti-CA and anti-MA). Panel 3, intracellular BST2 levels (CELLS, anti-BST2). The first lane of Panel 1 contains 25-fold less sample than the other lanes. Quantification showed that, on average, cells transfected with BST2(L70D) expressed 1.4 ± 0.3-fold more protein than those transfected with the wild-type BST2 (n = 5, ± s.d.). Nevertheless, cells expressing BST2(L70D) released 2.5 ± 1.3-fold more virion-associated CA and MA protein (n = 10, ± s.d.). (B) Graph showing HIV-1 titers in the presence of increasing quantities of expression vectors. Wild-type BST2 (light curve), BST2(L70D) (dark curve). Each data point corresponds to a sample analyzed in the Western blots shown in panel A. On average, viral titers were 1.9 ± 0.1-fold higher in cells expressing BST2(L70D) mutant (vs. wild-type BST2, n = 10, ± s.d.).