Figure 3

Unintegrated viral DNA in F-S MLV infected M. dunni cells and MA139 cells transfected with mCAT-1 or dCAT-1. Transfectant FerrM expresses mCAT-1 and the various FerrD transfectants express dCAT-1. (A) Southern blot of DNAs extracted by the Hirt method [25] three days after infection with F-S MLV. DNAs were cleaved with EcoRI and hybridized with a probe representing the segment of pol indicated by the black bar. (B) The 5.5 kb bands representing the pol-probe reactive cleavage product of linear viral DNA were quantified by densitometric scanning and compared to that of M. dunni, which was defined as 100%. (C) The indicated cultures of F-S MLV infected cells were photographed just before Hirt DNA extraction using objective lens magnification of 10×. The extent of virus induced fusion in each culture is indicated by the number of nuclei per cell and the proportion of nuclei in syncytia; numbers represent averages for 4–6 representative fields.