The ubiquitin ligase HERC3 attenuates NF-κB-dependent transcription independently of its enzymatic activity by delivering the RelA subunit for degradation

Nucleic Acids Res. 2015 Nov 16;43(20):9889-904. doi: 10.1093/nar/gkv1064. Epub 2015 Oct 17.

Abstract

Activation of NF-κB-dependent transcription represents an important hallmark of inflammation. While the acute inflammatory response is per se beneficial, it can become deleterious if its spatial and temporal profile is not tightly controlled. Classically, NF-κB activity is limited by cytoplasmic retention of the NF-κB dimer through binding to inhibitory IκB proteins. However, increasing evidence suggests that NF-κB activity can also be efficiently contained by direct ubiquitination of NF-κB subunits. Here, we identify the HECT-domain ubiquitin ligase HERC3 as novel negative regulator of NF-κB activity. We find that HERC3 restricts NF-κB nuclear import and DNA binding without affecting IκBα degradation. Instead HERC3 indirectly binds to the NF-κB RelA subunit after liberation from IκBα inhibitor leading to its ubiquitination and protein destabilization. Remarkably, the regulation of RelA activity by HERC3 is independent of its inherent ubiquitin ligase activity. Rather, we show that HERC3 and RelA are part of a multi-protein complex containing the proteasome as well as the ubiquitin-like protein ubiquilin-1 (UBQLN1). We present evidence that HERC3 and UBQLN1 provide a link between NF-κB RelA and the 26S proteasome, thereby facilitating RelA protein degradation. Our findings establish HERC3 as novel candidate regulating the inflammatory response initiated by NF-κB.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing
  • Animals
  • Autophagy-Related Proteins
  • Carrier Proteins / metabolism
  • Catalytic Domain
  • Cattle
  • Cell Cycle Proteins / metabolism
  • Cells, Cultured
  • DNA / metabolism
  • DNA-Binding Proteins / metabolism*
  • HEK293 Cells
  • Humans
  • I-kappa B Proteins / metabolism
  • NF-KappaB Inhibitor alpha
  • NF-kappa B / metabolism*
  • Proteasome Endopeptidase Complex / metabolism
  • Protein Stability
  • Transcription Factor RelA / metabolism*
  • Transcription, Genetic*
  • Ubiquitin-Protein Ligases / chemistry
  • Ubiquitin-Protein Ligases / metabolism
  • Ubiquitination

Substances

  • Adaptor Proteins, Signal Transducing
  • Autophagy-Related Proteins
  • Carrier Proteins
  • Cell Cycle Proteins
  • DNA-Binding Proteins
  • I-kappa B Proteins
  • NF-kappa B
  • NFKBIA protein, human
  • Transcription Factor RelA
  • UBQLN1 protein, human
  • NF-KappaB Inhibitor alpha
  • DNA
  • HERC3 protein, human
  • Ubiquitin-Protein Ligases
  • Proteasome Endopeptidase Complex