I kappa B-zeta is involved in the regulation of NF-kappa-B transcription factor complexes. I kappa B-zeta inhibits NF-kappa-B activity without affecting its nuclear translocation upon stimulation. It inhibits DNA-binding of RELA and NFKB1/p50, and of the NF-kappa-B p65-p50 heterodimer and the NF-kappa-B p50-p50 homodimer. It also seems to activate NF-kappa-B-mediated transcription. I kappa B-zeta seems to be involved in the induction of inflammatory genes activated through TLR/IL-1 receptor signaling, and may promote apoptosis [taken from the Universal Protein Resource (UniProt) www.uniprot.org/uniprot/Q9EST8].