FIG. 2.

Tunicamycin inhibits XC cell-specific syncytium formation by the R⁺ Env protein. 293T cells were transfected with the plasmid encoding the R⁻ or R⁺ Env protein of Mo-MLV (Mo) or Fr-MLV (Fr). XC and NIH 3T3 cells were pretreated with tunicamycin (50 or 100 ng/ml) for 24 h. The transfected 293T cells were added to the pretreated XC and NIH 3T3 cells and cultured for 24 h in the absence of tunicamycin. The cells were stained with 1% methylene blue, and the number of syncytia per microscopic field was determined. The error bars indicate standard deviations.