The protein encoded by this gene binds to components of NF-kappa-B, trapping the complex in the cytoplasm and preventing it from activating genes in the nucleus. Phosphorylation of the encoded protein targets it for destruction by the ubiquitin pathway, which activates NF-kappa-B by making it available to translocate to the nucleus. NFKBIE protein expression is up-regulated following NF-κB activation and during myelopoiesis. NFKBIE is able to inhibit NF-κB-directed transactivation via cytoplasmic retention of REL proteins. NFKB1 or NFKB2 is bound to REL, RELA, or RELB to form the NF-κB transcription factor complex. The NF-κB complex is inhibited by I-kappa-B proteins (NFKBIA or NFKBIB), which inactivate NF-kappa-B by trapping it in the cytoplasm.