Transcription factors of the nuclear factor κ B (NFκB)/Rel family play a pivotal role in inflammatory and immune responses . There are five family members in mammals: RelA, c-Rel, RelB, NFκB1 (p105/p50), and NFκB2 (p100/p52). Both p105 and p100 are proteolytically processed by the proteasome to produce p50 and p52, respectively. Rel proteins bind p50 and p52 to form dimeric complexes that bind DNA and regulate transcription. In unstimulated cells, NFκB is sequestered in the cytoplasm by IκB inhibitory proteins. NFκB-activating agents can induce the phosphorylation of IκB proteins, targeting them for rapid degradation through the ubiquitin-proteasome pathway and releasing NFκB to enter the nucleus where it regulates gene expression.
