title: The kinase TNIK is an essential activator of Wnt target genes.
abstract: Wnt signalling maintains the undifferentiated state of intestinal crypt/progenitor cells through the TCF4/beta-catenin-activating transcriptional complex. In colorectal cancer, activating mutations in Wnt pathway components lead to inappropriate activation of the TCF4/beta-catenin transcriptional programme and tumourigenesis. The mechanisms by which TCF4/beta-catenin activate key target genes are not well understood. Using a proteomics approach, we identified Tnik, a member of the germinal centre kinase family as a Tcf4 interactor in the proliferative crypts of mouse small intestine. Tnik is recruited to promoters of Wnt target genes in mouse crypts and in Ls174T colorectal cancer cells in a beta-catenin-dependent manner. Depletion of TNIK and expression of TNIK kinase mutants abrogated TCF-LEF transcription, highlighting the essential function of the kinase activity in Wnt target gene activation. In vitro binding and kinase assays show that TNIK directly binds both TCF4 and beta-catenin and phosphorylates TCF4. siRNA depletion of TNIK followed by expression array analysis showed that TNIK is an essential, specific activator of Wnt transcriptional programme. This kinase may present an attractive candidate for drug targeting in colorectal cancer.
authors.affiliation: Hubrecht Institute-KNAW and University Medical Centre Utrecht, Utrecht, The Netherlands.
authors.forename: Tokameh
authors.initials: T
authors.lastname: Mahmoudi
authors.forename: Vivian S W
authors.initials: VS
authors.lastname: Li
authors.forename: Ser Sue
authors.initials: SS
authors.lastname: Ng
authors.forename: Nadia
authors.initials: N
authors.lastname: Taouatas
authors.forename: Robert G J
authors.initials: RG
authors.lastname: Vries
authors.forename: Shabaz
authors.initials: S
authors.lastname: Mohammed
authors.forename: Albert J
authors.initials: AJ
authors.lastname: Heck
authors.forename: Hans
authors.initials: H
authors.lastname: Clevers
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000235:genetics / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007421:Intestine, Small / Q000378:metabolism / Q000648:ultrastructure; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D000073940:Transcription Factor 4; D015533:Transcriptional Activation; D051153:Wnt Proteins / Q000235:genetics*; D051176:beta Catenin / Q000378:metabolism
chemical_list: D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; C090743:Tcf4 protein, mouse; D000073940:Transcription Factor 4; D051153:Wnt Proteins; D051176:beta Catenin; D017346:Protein Serine-Threonine Kinases; C545105:TNIK protein, mouse