IkappaB kinase beta (IKKbeta) is involved in tumor development and progression through activation of the nuclear factor (NF)-kappaB pathway. However, the molecular mechanism that regulates IKKbeta 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 IKKbeta ubiquitination. Depletion of KEAP1 led to the accumulation and stabilization of IKKbeta and to upregulation of NF-kappaB-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 IKKbeta degradation. Our results suggest that the dysregulation of KEAP1-mediated IKKbeta ubiquitination may contribute to tumorigenesis.
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