Figure 5.

Combinatorial regulation of gene expression by sc-rtTA and tTS. Transcription from the CMV-7tetO luciferase reporter construct was measured upon transfection of C33A cells with the indicated rtTA, sc-rtTA (wild-type or with mutations in both TetR domains) and tTS expression plasmids or pBluescript (-) as a negative control, and a plasmid constitutively expressing Renilla luciferase to correct for differences in transfection efficiency. Cells were cultured with (1000 ng/ml) or without dox. The ratio of the firefly and Renilla luciferase activities measured two days after transfection reflects the rtTA activity. All values were related to the original (wild-type) sc-rtTA activity at 1000 ng/ml dox, which was arbitrarily set at 100%. Average values of three transfections are plotted with the error bars indicating the standard deviations. The ratio between the induced (+ dox) and uninduced (no dox) promoter activity (fold induction) is indicated on top of the bars.