Casein kinase I epsilon in the Wnt pathway: Regulation of beta-catenin function

Wnt and its intracellular effector beta-catenin regulate developmental and oncogenic processes. Using expression cloning to identify novel components of the Wnt pathway, we isolated casein kinase I epsilon (CKI epsilon). CKI epsilon mimicked Wnt in inducing a secondary axis in Xenopus, stabilizing b eta-catenin, and stimulating gene transcription in cells, Inhibition of end ogenous CKI epsilon by kinase-defective CKI epsilon or CKI epsilon antisens e-oligonucleotides attenuated Wnt signaling. CKI epsilon was in a complex w ith axin and other downstream components of the Wnt pathway, including Dish evelled, CKI epsilon appears to he a positive regulator of the pathway and a link between upstream signals and the complexes that regulate beta-cateni n.