Figure 6.

TCF3 knockdown alters proper regulation of MYC expression in synchronized cells. (A) qPCR analysis of MYC expression in cDNAs prepared from HCT116 cells expressing control or TCF3-specific shRNAs that were synchronized in the cell cycle. MYC transcripts were measured in quiescent cells (time 0), and in cells treated with media-containing serum for one, 2, 4, or 8 hours. At each time point, the data is normalized to GAPDH. (B) qPCR analysis of DNA fragments precipitated with anti-TCF4 antibodies in ChIP assays conducted in quiescent cells (time 0) or quiescent cells that were treated with media-containing serum for the number of hours indicated. TCF4 binding was assessed at the MYC 3′ WRE using oligonucleotides specific to the element in the qPCR reactions. (C) As in B, except ChIP assays were conducted with anti-β-catenin-specific antibodies. All experiments were repeated at least 3 times and error bars are ± SEM (*P < 0.05, **P < 0.01, **P < 0.001).