KEAP1 E3 Ligase-Mediated Downregulation of NF-κB Signaling by Targeting IKKβ

I kappa B kinase beta (IKK beta) is involved in tumor development and progression through activation of the nuclear factor (NF)-kappa B pathway. However, the molecular mechanism that regulates IKK beta degradation remains largely unknown. Here, we show that a Cullin 3 (CUL3)-based ubiquitin ligase, Kelch-like ECH-associated protein 1 (KEAP1), is responsible for IKK beta ubiquitination. Depletion of KEAP1 led to the accumulation and stabilization of IKK beta and to upregulation of NF-kappa B-derived tumor angiogenic factors. A systematic analysis of the CUL3, KEAP1, and RBX1 genomic loci revealed a high percentage of genome loss and missense mutations in human cancers that failed to facilitate IKK beta degradation. Our results suggest that the dysregulation of KEAP1-mediated IKK beta ubiquitination may contribute to tumorigenesis.