title: Alternative splicing of Tcf7l2 transcripts generates protein variants with differential promoter-binding and transcriptional activation properties at Wnt/beta-catenin targets.
abstract: Alternative splicing can produce multiple protein products with variable domain composition from a single gene. The mouse Tcf7l2 gene is subject to alternative splicing. It encodes TCF4, a member of the T-cell factor (TCF) family of DNA-binding proteins and a nuclear interaction partner of beta-catenin which performs essential functions in Wnt growth factor signalling. Multiple TCF4 isoforms, potentially exhibiting cell-type-specific distribution and differing in gene regulatory properties, could strongly influence tissue-specific Wnt responses. Therefore, we have examined mouse Tcf7l2 splice variants in neonatal tissues, embryonic stem cells and neural progenitors. By polymerase chain reaction amplification, cloning and sequencing, we identify a large number of alternatively spliced transcripts and report a highly flexible combinatorial repertoire of alternative exons. Many, but not all of the variants exhibit a broad tissue distribution. Moreover, two functionally equivalent versions of the C-clamp, thought to represent an auxiliary DNA-binding domain, were identified. Depending upon promoter context and precise domain composition, TCF4 isoforms exhibit strikingly different transactivation potentials at natural Wnt/beta-catenin target promoters. However, differences in C-clamp-mediated DNA binding can only partially explain functional differences among TCF4 variants. Still, the cell-type-specific complement of TCF4 isoforms is likely to be a major determinant for the context-dependent transcriptional output of Wnt/beta-catenin signalling.
authors.affiliation: Institute of Molecular Medicine and Cell Research, Center for Biochemistry and Molecular Cell Research, Spemann Graduate School of Biology and Medicine, Albert-Ludwigs-University Freiburg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Weise
authors.forename: Katja
authors.initials: K
authors.lastname: Bruser
authors.forename: Susanne
authors.initials: S
authors.lastname: Elfert
authors.forename: Britta
authors.initials: B
authors.lastname: Wallmen
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Wittel
authors.forename: Simon
authors.initials: S
authors.lastname: Wöhrle
authors.forename: Andreas
authors.initials: A
authors.lastname: Hecht
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D014644:Genetic Variation; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D051820:TCF Transcription Factors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D014018:Tissue Distribution; D058118:Transcription Factor 7-Like 2 Protein; D015533:Transcriptional Activation; D051153:Wnt Proteins / Q000494:pharmacology*; D051176:beta Catenin / Q000378:metabolism*
chemical_list: D020033:Protein Isoforms; D051820:TCF Transcription Factors; C544894:TCF7L2 protein, human; C544895:Tcf7l2 protein, mouse; D058118:Transcription Factor 7-Like 2 Protein; D051153:Wnt Proteins; D051176:beta Catenin