Heterokaryon assay cell counts.

aCOS-7 cells were transiently transfected with the various expression vectors, and 24 h later a heterokaryon assay was carried out with NIH 3T3 cells or COS-7 cells were infected with HSV-1, and 12 h later a heterokaryon assay was carried out with 3T3 cells.bMouse nuclei were considered positive if they were present in fused heterokaryons of COS-7 cells expressing VP19C-EYFP or mutant proteins and monkey 3T3 cells contained detectable levels of the expressed protein.cMouse nuclei were considered negative if they were present in fused heterokaryons of COS-7 cells expressing VP19C-EYFP or mutant proteins and monkey 3T3 cells did not contain detectable levels of the expressed protein.