FIG. 1.
Schematic drawing of the vector constructs used in this study. (A) HIV-1-based vector constructs containing an internal CMV promoter driving transgene expression. (B) HIV-1-based vector constructs in which transgene expression is driven by the HIV LTR promoter. The transgene is expressed from a spliced message. (C) MLV constructs containing an internal herpes simplex virus TK promoter (Tk) driving the expression of luciferase. The WPRE is shown as a black box. W(as) designates the WPRE inserted in the antisense orientation. Orientation is designated by arrows. SD, splice donor; SA, splice acceptor; RRE, Rev-responsive element; R, repeat region.