Figure 5.

(A) Structure of the truncated XGrg-4-QGP molecule compared to that of Grg-5. (B) Alignment of the GP domains of long Grg homologues with mGrg-5. The amino acid residues that are unique for mGrg-5 when compared to Gmgrg-1, Mgrg-3 and XGrg-4 are depicted in bold. (C) XGrg-4-QGP functions as a repressor, but mGrg-5 functions as a de-repressor for Tcf-mediated transcriptional activation. Mouse B cell line IIAI.6 was co-transfected with the Tcf reporter construct (TOP-TK) and XTcf-3 and Armadillo (the Drosophila β-catenin homologue). This results in transactivation and increase of luciferase activity. This transactivation is de-repressed when Grg-5 is co-transfected, whereas the transactivation is repressed upon co-transfection with a truncation of XGrg-4 that only contains the Q and GP domains. Transfections were performed in duplicate, and luciferase values were corrected for the efficiency of transfection using the internal Renilla transfection control pRNL-TK by determining the luciferase/Renilla ratio. This ratio is given on the y-axis.