FIGURE 4.

Enhanced counteraction of Vif R93E against the restriction by APOBEC3G. Single-cycle infection experiments were performed by using VSV-G pseudotyped luciferase reporter viruses produced in 293T cells by co-transfection of pNL43/ΔEnv-Luc with the indicated Vif phenotype and pVSV-G in the presence or absence of co-transfection of pcDNA3/HA-A3G. Virus-containing supernatant was added to fresh 293T cells, and the luciferase activity of the cell lysates was measured by adding substrate and using a luminometer. The value of the virus without vif mutation in the absence of APOBEC3G was normalized to 100%, and mean ± S.E. of three independent experiments is shown (top panel). *, p < 0.05; **, p < 0.01 (statistically significant differences of infectivity between wild-type and R93E-harboring viruses). The levels of APOBEC3G in cells and virions and Vif in cells were also analyzed by immunoblotting (bottom panel). Virus p24 capsid protein (CA) and cellular tubulin were used as control.