CK1δ/GSK3β/FBXW7α axis promotes degradation of the ZNF322A oncoprotein to suppress lung cancer progression

Overexpression of Cys2His2 zinc-finger 322A (ZNF322A) oncogenic transcription factor is associated with lung tumorigenesis. However, the mechanism of ZNF322A overexpression remains poorly understood. Here, we discover that protein stability of ZNF322A is regulated by coordinated phosphorylation and ubiquitination through the CK1δ/GSK3β/FBXW7α axis. CK1δ and GSK3β kinases sequentially phosphorylate ZNF322A at serine-396 and then serine-391. Moreover, the doubly phosphorylated ZNF322A protein creates a destruction motif for the ubiquitin ligase FBXW7α leading to ZNF322A protein destruction. Overexpression of FBXW7α induces ZNF322A protein degradation, thereby blocks ZNF322A transcription activity and suppresses ZNF322A-induced tumor growth and metastasis in vitro and in vivo. Clinically, overexpression of ZNF322A correlates with low FBXW7α or defective CK1δ/GSK3β-mediated phosphorylation in lung cancer patients. Multivariate Cox regression analysis indicates that patients with ZNF322A high/FBXW7 low expression profile can be used as an independent factor to predict the clinical outcome in lung cancer patients. Our results reveal a new mechanism of ZNF322A oncoprotein destruction regulated by the CK1δ/GSK3β/FBXW7α axis. Deregulation of this signaling axis results in ZNF322A overexpression and promotes cancer progression.