Cloning of the p50 DNA binding subunit of NF-κB: Homology to rel and dorsal

The DNA binding subunit of the transcription factor NF-κB, p50, has been cloned. p50 appears to be synthesized as a larger protein that is then processed to its functional size. Sequence analysis reveals remarkable homology for over 300 amino acids at the amino-terminal end to the oncogene v- rel, its cellular homolog c- rel, and the Drosophila maternal effect gene dorsal. This establishes NF-κB as a member of the rel family of proteins, all of which display nuclear-cytosolic translocation. Protein sequence from the p65 polypeptide has established that it is not encoded in the same mRNA as p50. However, p65 appears homologous to c- rel, suggesting that c- rel may form heterodimers with p50 and rel may include a homodimerization motif.