FIG. 7.

Mapping of IRES B. (A) Schematic drawing of the bicistronic constructs containing the complete or truncated VEGF 5′ UTR between the first CAT cistron and the second chimeric fCAT cistron (depicted in Fig. 2C). The 5′ and 3′ boundaries of the deletions are indicated. Western immunoblotting was performed (right) as described for Fig. 1B after transfection of COS-7 cells with plasmids A to E. The CAT and fCAT proteins are shown by arrows. The control (Ct) lane corresponds to untransfected cells. (B) Representation of bicistronic vectors containing a stable hairpin structure upstream from the LUCr gene (first cistron), fragments of the VEGF mRNA leader sequence in the intercistronic region, and the LUCf gene as the second cistron. The 5′ and 3′ boundaries of the deletions are indicated. These plasmids were transfected into COS-7 cells, and luciferase activities measured as described in Materials and Methods. On the right, the histogram and corresponding values represent the LUCf/LUCr activity ratio obtained with each construct and that obtained with pRHL. Each value represents the average of at least four independent transfection experiments.