Fig. 1. ß-catenin and ß-eng constructs and activity in HC11 cells. (A) Stabilized ß-catenin (*, SA, TA mutations in the N-terminal domain) and ß-eng constructs. The C-terminal domain of ß-catenin is replaced with the N-terminal repressor domain of Drosophila Engrailed to create ß-eng. These constructs were tested for ß-catenin signalling activity in HC11 mammary epithelial cells (B-C). Combinations of E-cadherin-luciferase reporter, either stabilized ß-catenin or ß-eng, and empty plasmid DNA were mixed to equivalent amounts of DNA and transfected into HC11 cells (B). These data show that stabilized ß-catenin upregulates transcription at the E-cadherin promoter, but ß-eng does not. Additionally, constant amounts of the E-cadherin reporter and stabilized ß-catenin were transfected into HC11 cells with increasing amounts of ß-eng (C). The activity of the reporter construct shows that the ß-catenin-mediated activation of E-cadherin transcription is effectively competed by ß-eng in stoichometric ratios with ß-catenin. The ß-eng chimera was cloned into two mammary-specific transgenic expression vectors, driven by the MMTV long terminal repeat or the WAP promoter (D). Both constructs contain six tandem myc tags, an intron 5' to the ß-eng construct and a growth hormone polyA sequence.