FIGURE 2. JNK-dependent interaction between c-Jun and TCF4 regulates the c-jun promoter.

a, Schematic representation of the human c-jun promoter. Numbers denote nucleotides relative to the transcriptional start site indicated by a bold arrow (+ 1). Open circles indicate regulatory DNA elements, crossed circles indicate mutated sites. Arrows indicate approximate positions of PCR primers used in chromatin immunoprecipitation analysis. b, TCF4 chromatin immunoprecipitation (ChIP) was performed using HCT116 cells. c, Chromatin immunoprecipitation for the Myc tag was performed on HCT116 cells transfected with Myc-tagged c-Jun or c-Jun^4A. d, -catenin chromatin immunoprecipitation was performed using TIG or HCT116 cells. Cells were treated for 1 h with JNK inhibitor or anisomycin (Anm) in b−d. e, HCT116 cells were transfected to express c-Jun, c-Jun^4A, TCF4, pSUPER or a pSUPER vector expressing a shRNA specific for -catenin (pS-sicat). Activity of a c-jun promoter firefly luciferase reporter construct (c-jun−luc) relative to a tk-renilla luciferase transfection control (tk-Rluc) is shown. f, HCT116 cells were transfected to express c-Jun, c-Jun^4A, TCF4, tk-Rluc and either c-jun−luc, c-jun−luc(mAP1) or c-jun−luc(mTCF). The luciferase activity of cells transfected with only c-jun−luc and tk-Rluc is arbitrarily set to 1 in e, f. Values in e, f are mean s.e.m. (standard error of the mean).