FIG. 3.

SOX2 disrupts β-catenin-TCF/LEF mediated transcriptional activation. A, Human embryonic kidney 293 cells were cotransfected with the TCF/LEF reporter construct TOPFLASH with human SOX2 expression construct alone (70 ng) or human β-catenin expression construct with variable amounts of SOX2 (1–70 ng). Increasing amounts of SOX2 led to dose-dependent repression of β-catenin-mediated activation of the reporter. B, SOX2 mutations disrupt the interaction with β-catenin. SOX2 mutant constructs were tested and compared with wild-type (WT) SOX2 using 20 ng TOPFLASH, 30 ng β-catenin, and 20 ng SOX2 expression construct. Truncating SOX2 mutations fail to repress β-catenin-mediated activation, showing levels of activation comparable to cotransfection with β-catenin alone or empty expression vector. Schematic representation of the SOX2 gene with approximate positions of the mutations is shown in the top right.