Subcellular distribution and transactivation potential of wt and mutant BCL9 and B9L. A and B, SW480 cells overexpressing FLAG-BCL9 or FLAG-BCL9-2, fixed and stained with antibodies against β-catenin and FLAG, as indicated in panels (the staining pattern of GFP-B9L was similar to that of FLAG-BCL9-2; not shown). C-E, TOPFLASH assays in SW480 and Wnt-stimulated HEK 293 cells (as indicated in panels), expressing wt or mutant FLAG-BCL9 or FLAG-BCL9-2 (see text). Control FOPFLASH assays were also conducted, but the values were less than 5% of TOPFLASH values and did not vary significantly between samples (not shown). Standard deviations are given by bars, and statistical significance relative to values from cells transfected with pCDNA3 (arbitrarily set to 100) is indicated above bars (*, p < 0.05; **, p < 0.001).