Eaf1 and Eaf2 negatively regulate canonical Wnt/β-catenin signaling

Abstract

SUMMARYEaf factors play a crucial role in tumor suppression and embryogenesis. To investigate the potential mechanism of Eaf activity, we performed loss-and gain-of-function assays in zebrafish using morpholino and mRNA injections, respectively. We found that eaf1 and eaf2 inhibit Wnt/β-catenin signaling, thereby modulating mesodermal and neural patterning in the embryo. Moreover, ectopic expression of eaf1 and eaf2 in embryos and cultured cells blocked β-catenin reporter activity. By immunoprecipitation, we also observed that Eaf1 and Eaf2 bound to the Armadillo repeat region and C-terminus of β-catenin, as well as to other β-catenin transcription complex proteins, such as c-Jun, Tcf and Axin, suggesting the formation of a novel complex. In addition, the N-terminus of Eaf1 and Eaf2 bound to β-catenin and exhibited dominant-negative activity, whereas the C-terminus appeared to either harbor a suppression domain or to recruit a repressor. Both the N-and C-terminus must be intact for Eaf1 and Eaf2 suppressive activity. Lastly, we demonstrate a conservation of biological activities for Eaf family proteins across species. In summary, our evidence points to a novel role for Eaf1 and Eaf2 in inhibiting canonical Wnt/β-catenin signaling, which might form the mechanistic basis for Eaf1 and Eaf2 tumor suppressor activity.

Negative feedback regulation of Wnt signaling via N-linked fucosylation in zebrafish

“…In contrast, canonical Wnt signaling is diminished. As has been recently reported for other Wnt inhibitors (Flowers et al, 2012; Hayes et al, 2013; Liu et al, 2013), the reduced expression of direct Wnt targets in slc35c1 expressing embryos is consistent with an inhibitory function of Slc35C1 on Wnt signaling. Reduced intensity of nuclear β-Catenin in the “core” region (future dorsal) and the immediate Wnt target boz prior to formation of the dorsal organizer are consistent with inhibition of maternal Canonical Wnt signaling.…”

EAF2 Suppresses Hypoxia-Induced Factor 1α Transcriptional Activity by Disrupting Its Interaction with Coactivator CBP/p300

“…While subsequent studies further supported its tumor suppressive activity in vivo (11,12), the molecular mechanisms underlying this tumor suppression activity remain largely unclear. Recently, though, using a zebrafish model, we found that EAF2 and EAF1, a homolog of EAF2, can negatively regulate canonical Wnt/␤-catenin signaling by binding to ␤-catenin, which may partially explain its tumor-suppressive function mechanistically (13). Interestingly, we have demonstrated that EAF2 can bind to and stabilize pVHL, a well-defined tumor suppressor involved in HIFdegradation under normoxia.…”

EZH2 promotes metabolic reprogramming in glioblastomas through epigenetic repression of EAF2-HIF1α signaling

“…Inactivation of EAF2 induces tumorigenesis in several organs, including lung, liver and prostate [22]. Although its mechanism of action is unknown, studies show that EAF2 functions in controlling the growth and survival of cancer cells by negatively regulating canonical Wnt/β-catenin signaling as well as the RAS-BRAF-ERK signaling pathway [23, 24]. EAF2 also reportedly binds to and stabilizes von Hippel-Lindau protein (pVHL), a tumor suppressor involved in mediating HIF1α degradation and an inhibitor of the hypoxia pathway, which suggests it is a potential metabolic regulator [25].…”