Fig. 1: BCL9, Pygo2, LDB1 and SSBP2 form a stable complex in vitro.
a Domain structures of key components of the human Wnt enhanceosome; the double slash indicates shortening of the extensive C-terminus typical of BCL9-related proteins, which contains the binding site for Groucho/TLE and is required for Wnt responses in flies and human cells25,32; ARM-repeat (β-catenin Armadillo repeat), BID (β-catenin-binding domain), HMG (high mobility group), HD1/2/3 (homology domain 1/2/3), NHD (N-terminal homology domain of Pygo comprising an NLS, the PPP cluster and NPF motif), PHD (plant homology domain), DD (dimerization domain), LCCD (LDB/Chip conserved domain), LID (LIM-interaction domain), LUFS (LUG/LUH, Flo8 and SSBP conserved domain). b Co-migration of BCL9-Pygo2 and LDB1-SSBP2 complexes (both consisting of full-length human proteins) on size-exclusion chromatography (using a Superose 6 increase 10/300 GL column). Experiments were independently performed three times with similar results. c Diagram of human wt or truncated BCL9 tested for interaction with LDB1-SSBP2. d Binding-affinities of full-length or truncated forms of Avi-tagged BCL9-Pygo2 with full-length LDB1-SSBP2 complex, as measured by BLI assays. The KD was calculated based on steady-state analysis and was presented as mean values ± standard deviations (SD). n = 4 of analyzed concentrations. e A schematic model of the Wnt enhanceosome in its OFF or ON state (see also refs. 32,52); the red dashed circle marks the Pygo2-LDB1-SSBP2 ternary complex whose crystal structure is reported here. Note also that the HMG domain of TCF bends DNA53,54, which may facilitate assembly of transcriptional complex. Source data are provided as a Source Data file.
