title: Acetylation of human TCF4 (TCF7L2) proteins attenuates inhibition by the HBP1 repressor and induces a conformational change in the TCF4::DNA complex.
abstract: The members of the TCF/LEF family of DNA-binding proteins are components of diverse gene regulatory networks. As nuclear effectors of Wnt/β-catenin signaling they act as assembly platforms for multimeric transcription complexes that either repress or activate gene expression. Previously, it was shown that several aspects of TCF/LEF protein function are regulated by post-translational modification. The association of TCF/LEF family members with acetyltransferases and deacetylases prompted us to investigate whether vertebrate TCF/LEF proteins are subject to acetylation. Through co-expression with p300 and CBP and subsequent analyses using mass spectrometry and immunodetection with anti-acetyl-lysine antibodies we show that TCF4 can be acetylated at lysine K₁₅₀ by CBP. K₁₅₀ acetylation is restricted to TCF4E splice variants and requires the simultaneous presence of β-catenin and the unique TCF4E C-terminus. To examine the functional consequences of K₁₅₀ acetylation we substituted K₁₅₀ with amino acids representing the non-acetylated and acetylated states. Reporter gene assays based on Wnt/β-catenin-responsive promoter regions did not indicate a general role of K₁₅₀ acetylation in transactivation by TCF4E. However, in the presence of CBP, non-acetylatable TCF4E with a K₁₅₀R substitution was more susceptible to inhibition by the HBP-1 repressor protein compared to wild-type TCF4E. Acetylation of K₁₅₀ using a bacterial expression system or amino acid substitutions at K₁₅₀ alter the electrophoretic properties of TCF4E::DNA complexes. This result suggests that K₁₅₀ acetylation leads to a conformational change that may also represent the mechanism whereby acetylated TCF4E acquires resistance against HBP1. In summary, TCF4 not only recruits acetyltransferases but is also a substrate for these enzymes. The fact that acetylation affects only a subset of TCF4 splice variants and is mediated preferentially by CBP suggests that the conditional acetylation of TCF4E is a novel regulatory mechanism that diversifies the transcriptional output of Wnt/β-catenin signaling in response to changing intracellular signaling milieus.
authors.affiliation: Institute of Molecular Medicine and Cell Research, Albert-Ludwigs-University Freiburg, Freiburg, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Elfert
authors.forename: Andreas
authors.initials: A
authors.lastname: Weise
authors.forename: Katja
authors.initials: K
authors.lastname: Bruser
authors.forename: Martin L
authors.initials: ML
authors.lastname: Biniossek
authors.forename: Sabine
authors.initials: S
authors.lastname: Jägle
authors.forename: Niklas
authors.initials: N
authors.lastname: Senghaas
authors.forename: Andreas
authors.initials: A
authors.lastname: Hecht
mesh_terms: D000107:Acetylation; D000595:Amino Acid Sequence; D000818:Animals; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D050882:CREB-Binding Protein / Q000378:metabolism; D004247:DNA / Q000737:chemistry* / Q000378:metabolism*; D057809:HEK293 Cells; D006609:High Mobility Group Proteins / Q000378:metabolism*; D006801:Humans; D008239:Lysine / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000378:metabolism*; D013379:Substrate Specificity; D000073940:Transcription Factor 4; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D015533:Transcriptional Activation; D051176:beta Catenin / Q000378:metabolism
chemical_list: D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; C486328:HBP1 protein, human; D006609:High Mobility Group Proteins; D020033:Protein Isoforms; D012097:Repressor Proteins; C532096:TCF4 protein, human; D000073940:Transcription Factor 4; D014157:Transcription Factors; D051176:beta Catenin; D004247:DNA; D050882:CREB-Binding Protein; D008239:Lysine