NF-κB is a transcription factor that, in vertebrates, plays an important part in the transcription of genes related to immune functions. It was originally identified as a transcription factor that increases the production of of the κ light chain of immunoglobulin.
The Human Genome Project has identified 6 separate NF-κB genes. NF-κB functions as a dimer. This means that there may be as many as 36 different functional NF-κB combinations. Much of what is known of NF-κB function deals with the p50 and p65 forms of NF-κB.
The regulation of NF-κB is through its interaction with a protein called IκB. When IκB is around, it binds NF-κB, and keeps it in the cytoplasm, preventing its function as a transcription factor. When certain stimuli need to activate NF-κB, IκB is phosphorylated. This phosphorylation leads to polyubiquitination, and eventual degradation by a proteasome dependent degradation. Once IκB is degraded, NF-κB is free to translocate to the nucleus to bind appropriate sites in the regulatory region of inflammatory genes. Studies have also shown a further level of regulation of NF-κB activity by direct phosphorylation of NF-κB.