The v-sis oncoprotein loses transforming activity when targeted to the early Golgi complex

To examine the subcellular location of v-sis fusion proteins, NIH3T3 cells were transfected with MLV expression constructs and then processed for immunofluorescence. The proteins were detected by an antibody to the v-sis portion of the fusion proteins. As visualized in the permeabilized cells shown in Fig. 4 , there was a high level of expression for all the fusion proteins presented in this figure (see Fig. 4 , A, C, E, and G). Staining can be seen of the ER and Golgi of these cells, indicating the presence of these fusion proteins throughout the secretory compartment. The cells depicted in Fig. 4 are representative of the positive cells seen in these transient expression assays. The percentage of cells expressing the desired constructs typically ranged from ,,ol-5 %.