FIG. 7.

The actin cytoskeleton and Rac activation in virus-dependent cell fusion. Fusion of U87.CD4.CCR5.GFP cells incubated with increasing amounts (A) or 100 ng of HIV_YU2 per well (B to D) at 37°C (except where noted in B). In panels A to C, relative fusion is indicated by β-galactosidase activity (average A₅₇₉ of triplicate wells ± standard deviation; data are representative of results from three similar experiments). (D) U87.CD4.CCR5.GFP cells were infected with WT vaccinia or vaccinia viruses encoding the dominant-negative point mutants Cdc42N17, RacN17, or RhoN19 as indicated, prior to incubation with HIV_HXB2 (upper panels) or HIV_YU2 (lower panels), fixation, and confocal microscopy. Images were collected by using an oil objective (magnification, ×63). The experiment was performed twice with similar results.