Fig. 2

DOX induces MBP-controlled luciferase expression in a dose-dependent manner. Human oligodendroglioma (HOG) cells were transfected via electroporation with a construct similar to that in Figure 1, using the MBP promoter and luciferase as a reporter gene. Forty-eight hours later, DOX was added at the indicated concentrations and incubated for 24 hr, after which luciferase activity and protein content were analyzed (left panel). Means ± SD of three replicates are shown. Right panel: Schematic illustration of the postulated mechanism of graded luciferase expression. In the presence of more DOX, there are more tet transactivators bound to TREs, leading to a stronger activation of CMV promoter and a greater expression of luciferase by oligodendrocytes.