Figure 3.

The apoptotic effects of β-catenin are independent of its transactivating function with LEF-1. (A) Different β-catenin constructs were expressed in NIH 3T3 fibroblasts. Full-length (FL), C-terminal–deleted (delC), and Arm β-catenin were detected by GFP fluorescence mostly in the nucleus, where they formed distinct aggregates. N-terminal–deleted (delN) β-catenin accumulated mostly in cytoplasm. GFP, control empty GFP transfection. Bar, 50 μm. (B) The presence of exogenous β-catenin was confirmed by Western blot analysis with the use of anti-β-catenin and anti-GFP antibodies. Exogenous full-length and ΔN1–86 β-catenins were detected as bands (119 and 110 kDa, respectively) by these two antibodies. Because anti-β-catenin antibody was raised against the immunogen of C-terminal residues (571–781 amino acids) in β-catenin, ΔC β-catenin (ΔC669–781) and Arm β-catenin (ΔN1–86 and ΔC669–781) showed very faint bands (108 and 99 kDa, respectively) by anti-β-catenin antibody. However, the presence of exogenous ΔC and Arm β-catenin was clearly confirmed with anti-GFP antibody (bottom panel). (C) Full-length and ΔN β-catenin are able to transactivate TOPFLASH-Luc reporter containing TCF/LEF-1–binding motifs, whereas Arm β-catenin totally abolishes the transactivating function. ΔC β-catenin shows only marginal transactivation (1.3-fold). FOPFLASH reporter, containing mutant binding sites, is not activated by any of the β-catenin constructs. (D) Arm β-catenin does not have any transactivating activity with TCF/LEF-1 but still was able to induce apoptosis.