Sp5 and Sp8 recruit ?-catenin and Tcf1-Lef1 to select enhancers to activate Wnt target gene transcription.

ABSTRACT: The ancient, highly conserved, Wnt signaling pathway regulates cell fate in all metazoans. We have previously shown that combined null mutations of the specificity protein (Sp) 1/Klf-like zinc-finger transcription factors Sp5 and Sp8 (i.e., Sp5/8) result in an embryonic phenotype identical to that observed when core components of the Wnt/?-catenin pathway are mutated; however, their role in Wnt signal transduction is unknown. Here, we show in mouse embryos and differentiating embryonic stem cells that Sp5/8 are gene-specific transcriptional coactivators in the Wnt/?-catenin pathway. Sp5/8 bind directly to GC boxes in Wnt target gene enhancers and to adjacent, or distally positioned, chromatin-bound T-cell factor (Tcf) 1/lymphoid enhancer factor (Lef) 1 to facilitate recruitment of ?-catenin to target gene enhancers. Because Sp5 is itself directly activated by Wnt signals, we propose that Sp5 is a Wnt/?-catenin pathway-specific transcript on factor that functions in a feed-forward loop to robustly activate select Wnt target genes.

SUBMITTER: Kennedy MW 

PROVIDER: S-EPMC4822596 | biostudies-literature | 2016 Mar

REPOSITORIES: biostudies-literature