Interaction between the Krüppel‐like zinc finger protein Glis2 and Wnt/β‐catenin signaling

Abstract

Gli-similar (Glis) 1–3 constitute a subfamily of Krüppel-like zinc finger proteins that are closely related to members of the Gli subfamily. These proteins play a critical role in embryonic development and have been implicated in a number of diseases including cancer. Members of Gli and Glis subfamilies share a highly conserved zinc finger domain consisting of five Cys2His2-type zinc finger motifs. This zinc finger domain mediates the binding of these proteins to Gli-binding sites (GBS), bearing consensus sequence ACCACCCAC in the regulatory region of target genes. Glis2 regulates gene transcription by directly interacting with GBS but Glis proteins may also regulate gene expression through crosstalk with other signaling pathways. To gain insight into the mechanisms by which Glis2 regulates gene transcription, we performed yeast-two hybrid cDNA library screening using Glis2 as bait. This screening identified β-catenin as a potential Glis2-interacting protein. Mammalian two-hybrid, co-immunoprecipitation, and GST-pulldown analyses supported the interaction between Glis2 and β-catenin. Pulldown analyses with several Glis2 deletion mutants indicated that the 1st zinc finger motif of Glis2 is critical for its interaction with β-catenin, while the armadillo repeats of β-catenin are important in its interaction with Glis2. Reporter analyses showed that Glis2 represses T-Cell Factor (TCF)-mediated transcriptional activation. In addition, Glis2 represses the expression of cyclin D1, a well-known Wnt target gene. Our results indicate that Glis2 interacts with β-catenin and suggest that Glis2 functions as a negative regulator of Wnt/β-catenin-mediated transcription.