NF-kappa-B/Dorsal (IPR000451)

Short name: NFkB/Dor

Overlapping homologous superfamilies


Family relationships


The transcription factor NF-kB (Nuclear Factor-kappaB) was first identified as a DNA-binding protein specific for the 10-base pair kB site in the immunoglobulin k light-chain enhancer of B lymphocytes [PMID: 17114415], but has subsequently been found in many different cell types. NF-kB represents a group of structurally related proteins that share a 300 amino acid `Rel homology domain' (RHD) [PMID: 2018779]: members include p50 (NF-kB1), p52 (NF-kB2), p65 (RelA), c-Rel, v-Rrel, RelB, and the Drosophila proteins Dorsal and Dif. These proteins exist as homo- and heterodimers that bind to kB sites in the enhancer regions of several target genes, most of which are involved in cellular defence mechanisms and differentiation.

The RHD, which is located N-terminally, is responsible for protein dimerisation, DNA binding and nuclear localisation. The more variable C-terminal transactivation domain is found in RelA, RelB and c-Rel, but not in p50 or p52. Nevertheless, p50 and p52 play critical roles in modulating the specificity of NF-kB function. DNA binding requires the entire RHD, by contrast with other eukaryotic and prokaryotic transcription factors, where much smaller DNA-binding domains confer full specificity and binding affinity for the target [PMID: 7530332]. The structure of the transcription factor NF-kB p50 homodimer bound to a palindromic kB site shows the RHD to fold into 2 distinct subdomains, similar to the beta-sandwich structure of the immunoglobulins [PMID: 7530332].

NF-kB is expressed in the cytoplasm of virtually all cell types, where its activity is controlled by a family of regulatory proteins, called inhibitors of NF-kB (IkB) [PMID: 15371334, PMID: 22302935].

GO terms

Biological Process

GO:0006355 regulation of transcription, DNA-templated

Molecular Function

GO:0003700 DNA-binding transcription factor activity

Cellular Component

GO:0005737 cytoplasm
GO:0005634 nucleus

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.