N-terminal sub-domain of the Rel homology domain (RHD) of nuclear factor of kappa B1 (NF-kappa B1)
Proteins containing the Rel homology domain (RHD) are metazoan transcription factors. The RHD is composed of two structural sub-domains; this model characterizes the N-terminal RHD sub-domain of the NF-kappa B1 family of transcription factors, a class I member of the NF-kappa B family. In class I NF-kappa Bs, the RHD domain co-occurs with C-terminal ankyrin repeats. NF-kappa B1 is commonly referred to as p105 or p50 (proteolytically processed form). NF-kappa B proteins are part of a protein complex that acts as a transcription factor, which is responsible for regulating a host of cellular responses to a variety of stimuli. This complex tightly regulates the expression of a large number of genes, and is involved in processes such as adaptive and innate immunity, stress response, inflammation, cell adhesion, proliferation and apoptosis. The cytosolic NF-kappa B complex is activated via phosphorylation of the ankyrin-repeat containing inhibitory protein I-kappa B, which dissociates from the complex and exposes the nuclear localization signal of the heterodimer (NF-kappa B and REL). NF-kappa B1 is involved in the canonical NF-kappa B signaling pathway which is activated by many agonists and is essential in immune and inflammatory responses, as well as cell survival. p105 is involved in its own specific NF-kappa B signaling pathway which is also implicated in immune and inflammatory responses. p105 may also act as an I-kappa B due to its C-terminal ankyrin repeats. It is also involved in mitogen-activated protein kinase (MAPK) signaling as its degradation leads to the activation of TPL-2, a MAPK kinase kinase which activates ERK pathways.