Figure 6.

Transcription activation induced by TβRI variants. Panel A. Transcriptional activation of TβRI variants. R1B cells were transiently transfected with 1 μg of either wild-type (WT) TβRI or truncated variants, as indicated in the bottom, 1 μg of p3TP-Lux, and 0.05 μg of pRL-TK plasmid which was used to correct the differences in transfection efficiency between experiments. After transfection for 24 h, the cells were treated with TGFβ1 (5 ng/mL) for 24 h and luciferase activities in each lysates were determined using a dual-luciferase reporter assay system (Promega). Data are the mean ± SEM luciferase activities of four independent experiments normalized to individual protein level. Panel B. Effects of TβRI variants on TGFβ-induced cell growth. R1B cells were transfected with each variant gene as indicated. The cell growth rates of the transfectants in the presence or absence of TGFβ1 were determined using standard MTT assays as described in the "Methods" section. Data are presented as the mean ± SEM of OD₅₅₀ absorbance values of three independent experiments.