RelA 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. Each Rel member bears a characteristic 300 amino acid N-terminal Rel homology domain (RHD) that functions to mediate DNA binding, dimerization, nuclear localization, and inhibitor association.