FIG. 9.

Syncytium-negative p10 constructs do not complement each other or exert a dominant-negative effect on syncytium formation. Cells were cotransfected in a pairwise fashion either with equal proportions of plasmids expressing different syncytium-negative p10 constructs or with functional p10-2HAN in combination with each of the syncytium-negative p10 constructs. Syncytium-negative p10 constructs included the substitutions in the TM domain (G49/50A), dicysteine motif (C63S), or basic region (K67M) described in this report, as well as several syncytium-negative constructs carrying substitutions in the p10 ectodomain. Transfected monolayers were observed for transfection efficiency and syncytium formation over time by immunostaining as described in the legend to Fig. 2 and were scored as syncytial (S) or nonsyncytial (NS). None of the syncytium-negative p10 constructs exerted a dominant-negative effect on syncytium formation induced by p10-2HAN, and the syncytium-negative p10 constructs were unable to complement each other.