FIG. 3.

Promoters of Wnt-inducible target genes are occupied by endogenous TCF4 irrespective of pathway activity. (A) ChIP analysis for TCF4 in C17.2, C2C12, or E14 cells. Cells were stimulated for 24 h with 25 μM (C17.2, C2C12) or 5 μM (E14) SB-216763 or with DMSO as the solvent control. Formaldehyde-fixed chromatin was precipitated using 2 μg of a TCF4-specific antibody or 2 μg of a nonspecific goat IgG as control. Precipitated DNA was analyzed by PCR using primer sets indicated in Fig. 1 with close proximity to TCF-binding elements in the Axin2, Cdx1, and T/Bra promoters. Primers within the coding region of the GAPDH gene, which is not regulated by TCFs, were used to monitor nonspecific precipitation. Control PCRs received no template (no templ.) or genomic DNA as the positive control. (B) Quantitative real-time PCR of ChIP DNA from C17.2, C2C12, and E14 cells as described above. For each gene, precipitated DNA was analyzed using multiple primer sets. Numbers refer to nucleotide positions of the amplicons relative to the transcriptional start site as indicated in Fig. 1. Bars represent relative enrichment compared to that of the nonspecific isotype control (relative enrichment of 1). Data given are the average and SEM from at least three experiments. α-, anti-.