Fig. 2. Hypothesized dual role of CK2 in the Wnt signaling pathway. Direct phosphorylation by CK2 prevents ß-catenin degradation, counteracting the effect of GSK3 phosphorylation within the negative regulatory complex (Son et al., 2000). On the other hand, CK2, by phosphorylating the E2 ubiquitin-conjugating enzyme UBC3, promotes its binding to the proteasome receptor ß-TrCP, ultimately assisting the degradation of ß-catenin (Semplici et al., 2002).