FIG. 1.
(A) Schematic representation of the two full-length GFP vectors. For details, see the text and reference 6. IRES, internal ribosome entry site. (B) Transmobilization of full-length SFV replicon by retrovirus particles. BHK-21 cells were cotransfected by a mix of RNAs. Supernatants from transfected cells were harvested to transduce 293T cells. Titers are expressed in transducing units per milliliter. Each column in the graph is associated with a specific mix of plasmids identified by plus symbols in light gray boxes. Within the graph, titers in dark gray represent GFP mobilization, while light gray columns reflect LacZ titers. GFP titers obtained with the 26Sm2 construct, in the presence or absence of a competitive LacZ SFV vector, were in the same order of magnitude. 26Sm2 ΨMLV-minus vector was almost as efficiently packaged as 26Sm2, its Ψ-positive counterpart. pSFV3, a LacZ-expressing, ΨMLV-minus SFV vector harboring a functional 26S internal promoter, was also efficiently mobilized. Cell debris-releasing RNA or GFP do not support transfer, as proved by the absence of GFP-positive cells when using 26Sm2 alone. Altogether, these data indicated that retrovirus particles are a vehicle for SFV vectors. Titers are means of results from at least five independent experiments.