The NFKB1 gene encodes a 105 kDa protein that can undergo co-translational processing to also yield a 50 kDa protein. The 50 kDa protein is also known as NF-kappa B1/p50 and is one of five monomeric subunits that are part of the Rel family of proteins that dimerize to form the NF-kappa B (nuclear factor that binds the kappa immunoglobulin light chain gene enhancer) transcription factor. Members of the Rel family of proteins include NF-kappa B1/p50, NF-kappa B2/p52, RelA/p65, c-Rel, and RelB. The 105 kDa product is also known as p105 or I kappa B gamma. p105/I kappa B gamma has been shown to function as an inhibitor protein that interacts with NF-kappa B and inhibit its DNA binding activity. p105/I kappa B gamma is a member of the I kappa B family of proteins which includes I kappa B-beta, I kappa B-delta/NF-kappa B2/p100, I kappa B-gamma/NF-kappa B1/p105, I kappa B-epsilon, I kappa B-zeta, and Bcl3. The classical description of the NF-kappa B transcription factor is a transcription factor that reprograms gene expression of the immune system in response to injury, infection, and stress.