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NF-κB is a pleiotropic transcription factor involved in multiple processes, including inflammation and oncogenesis. We have previously reported that COMMD1 represses κB-dependent transcription by negatively regulating NF-κB–chromatin interactions. Recently, ubiquitination of NF-κB subunits has been similarly implicated in the control of NF-κB recruitment to chromatin. We report here that COMMD1 accelerates the ubiquitination and degradation of NF-κB subunits through its interaction with a multimeric ubiquitin ligase containing Elongins B and C, Cul2 and SOCS1 (ECSSOCS1). COMMD1-deficient cells demonstrate stabilization of RelA, greater nuclear accumulation of RelA after TNF stimulation, de-repression of several κB-responsive genes, and enhanced NF-κB-mediated cellular responses. COMMD1 binds to Cul2 in a stimulus-dependent manner and serves to facilitate substrate binding to the ligase by stabilizing the interaction between SOCS1 and RelA. Our data uncover that ubiquitination and degradation of NF-κB subunits by this COMMD1-containing ubiquitin ligase is a novel and critical mechanism of regulation of NF-κB-mediated transcription. [ABSTRACT FROM AUTHOR]

NF-kappaB is a pleiotropic transcription factor involved in multiple processes, including inflammation and oncogenesis. We have previously reported that COMMD1 represses kappaB-dependent transcription by negatively regulating NF-kappaB-chromatin interactions. Recently, ubiquitination of NF-kappaB subunits has been similarly implicated in the control of NF-kappaB recruitment to chromatin. We report here that COMMD1 accelerates the ubiquitination and degradation of NF-kappaB subunits through its interaction with a multimeric ubiquitin ligase containing Elongins B and C, Cul2 and SOCS1 (ECS(SOCS1)). COMMD1-deficient cells demonstrate stabilization of RelA, greater nuclear accumulation of RelA after TNF stimulation, de-repression of several kappaB-responsive genes, and enhanced NF-kappaB-mediated cellular responses. COMMD1 binds to Cul2 in a stimulus-dependent manner and serves to facilitate substrate binding to the ligase by stabilizing the interaction between SOCS1 and RelA. Our data uncover that ubiquitination and degradation of NF-kappaB subunits by this COMMD1-containing ubiquitin ligase is a novel and critical mechanism of regulation of NF-kappaB-mediated transcription.