"Two optimal TCF binding sites, G(A/T)(A/T)CAAAG, are found in the genomic promoter fragment used to generate the
end-1 GFP reporter--GTTCAAAG beginning at -164 relative to the AUG translation initiation and GAACAAAG at -953. We mutated each site individually to G(A/T)(A/T)CGGGG, a change shown to abolish binding by the HMG domain (Korswagen et al., 2000). The
end-1 reporter with the -164 TCF binding site mutated exhibited low level basal expression in both the MS and E lineages (Figs. 2i, j), similar to the expression observed for the wild-type
end-1 reporter in the
pop-1 mutant."