Tumor necrosis factor-α induces RelA degradation via ubiquitination at lysine 195 to prevent excessive nuclear factor-κB activation

Abstract

Ubiquitination-mediated degradation of the RelA subunit of nuclear factor-κB (NF-κB) is critical for the termination of NF-κB activation. However, the precise mechanism for the ubiquitination of RelA is still not fully understood. Here we report that tumor necrosis factor-α(TNFα) induces RelA polyubiquitination at the lysine 195 residue, and this ubiquitination event is critical for the degradation of RelA and termination of TNFα-mediated NF-κB activation. Overexpression of a RelA mutant with an arginine substitution for the lysine 195 residue dramatically inhibits RelA polyubiquitination and induces a stronger NF-κB activation compared with the wild type. Reconstitution of RelA-deficient mouse embryo fibroblast cells with wild-type RelA or RelA containing a K195R mutation revealed the importance of this site in TNFα-mediated RelA polyubiquitination, degradation, and attenuation of NF-κB activation. Our finding is the first report that substitution of a key RelA lysine residue with arginine inhibits TNFα-induced RelA ubiquitination and enhances TNFα-induced NF-κB activation. © 2009 by The American Society for Biochemistry and Molecular Biology, Inc.