May modulate activity of cullin-RING E3 ubiquitin ligase (CRL) complexes (PubMed:21778237). Down-regulates activation of NF-kappa-B. Inhibits TNF-induced NFKB1 activation. Homodimer. Can only homodimerize with isoform 1. Interacts directly with COMMD1 (via COMM domain). Interacts with RELA, RELB, NFKB1/p105. Does not interact with NFKBIB. Interacts with CCDC22, CCDC93, SCNN1B, CUL4A. Ubiquitous. Expressed in brain, heart, skeletal muscle, lung, pancreas, liver, kidney, small intestine and placenta.