The Rel homology domain (RHD) is a protein domain found in a family of eukaryotic transcription factors,[2] including both NF-κB and NFAT, among others.

Some of these transcription factors appear to form multi-protein DNA-bound complexes.

[3] Phosphorylation of the RHD appears to play a role in the regulation of some of these transcription factors, acting to modulate the expression of their target genes.

[4] The RHD is composed of two immunoglobulin-like beta barrel subdomains that grip the DNA in the major groove.

The dimerization subdomain is immediately followed by a nuclear localization sequence that also comprises the site for inhibitory interactions with IκB.