title: Physical and functional cooperation between AP-1 and beta-catenin for the regulation of TCF-dependent genes.
abstract: Stabilization of cytoplasmic beta-catenin is a hallmark of a variety of cancers. The stabilized beta-catenin is able to translocate to the nucleus, where it acts as a transcriptional activator of T-cell factor (TCF)-regulated genes. beta-Catenin may cross-talk with many signalling cascades to activate target genes. Whether beta-catenin cooperates with AP-1, another transcriptional complex activated during tumorigenesis is not fully clarified. We show that beta-catenin co-immunoprecipitates with c-Jun and c-Fos. GST pull-down experiments indicate a physical association of the armadillo repeat domain of beta-catenin with the DNA-binding domain of c-Jun and of the C-terminal domain of beta-catenin with the N-terminal domain of c-Fos. Promoter studies indicate that overexpression of AP-1 activates the transcription of two beta-catenin target genes, cyclin D1 and c-myc, by a mechanism independent of the AP-1 site, and fully dependent on the TCF-binding site. We further demonstrate that AP-1/beta-catenin synergism is involved during serum-induced cyclin D1 transcriptional activation. We identify a TCF-binding site on the cyclin D1 promoter which binds in vivo a complex induced by serum, containing beta-catenin, TCF4, c-Fos, c-Jun, JunB and JunD. This novel mechanism of interaction between two signalling cascades might contribute to the potentiation of malignancy.
authors.affiliation: INSERM, U697, Paris, France.
authors.forename: K
authors.initials: K
authors.lastname: Toualbi
authors.forename: M C
authors.initials: MC
authors.lastname: Güller
authors.forename: J-L
authors.initials: JL
authors.lastname: Mauriz
authors.forename: C
authors.initials: C
authors.lastname: Labalette
authors.forename: M-A
authors.initials: MA
authors.lastname: Buendia
authors.forename: A
authors.initials: A
authors.lastname: Mauviel
authors.forename: D
authors.initials: D
authors.lastname: Bernuau
mesh_terms: D000818:Animals; D001665:Binding Sites; D049109:Cell Proliferation; D002478:Cells, Cultured; D003470:Culture Media / Q000494:pharmacology; D019938:Cyclin D1 / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D011401:Promoter Regions, Genetic; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D051820:TCF Transcription Factors / Q000235:genetics / Q000378:metabolism*; D018808:Transcription Factor AP-1 / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism*
chemical_list: D003470:Culture Media; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D016271:Proto-Oncogene Proteins c-myc; D051820:TCF Transcription Factors; D018808:Transcription Factor AP-1; D051176:beta Catenin; D019938:Cyclin D1