The NFκB transcription factor was originally identified as a protein complex consisting of a DNA binding subunit and an associated protein. The DNA binding subunit is functionally related to c-Rel p75 and Rel B p68. The p50 subunit was initially believed to be a functionally unique protein derived
from the amino terminus of a precursor designated p105. Rel B does not bind with high affinity to NFκB sites, but heterodimers between Rel B and p50 bind with an affinity comparable to that of p50 NFκB homodimers.NF-kappa-B heterodimeric RelB-p50 and RelB-p52 complexes are transcriptional activators. RELB neither associates with DNA nor with RELA/p65 or REL.
