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/?-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 K??? by CBP. K??? acetylation is restricted to TCF4E splice variants and requires the simultaneous presence of ?-catenin and the unique TCF4E C-terminus. To examine the functional consequences of K??? acetylation we substituted K??? with amino acids representing the non-acetylated and acetylated states. Reporter gene assays based on Wnt/?-catenin-responsive promoter regions did not indicate a general role of K??? acetylation in transactivation by TCF4E. However, in the presence of CBP, non-acetylatable TCF4E with a K???R substitution was more susceptible to inhibition by the HBP-1 repressor protein compared to wild-type TCF4E. Acetylation of K??? using a bacterial expression system or amino acid substitutions at K??? alter the electrophoretic properties of TCF4E::DNA complexes. This result suggests that K??? 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/?-catenin signaling in response to changing intracellular signaling milieus.

SUBMITTER: Elfert S 

PROVIDER: S-EPMC3626699 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature