RELB, A NEW REL FAMILY TRANSCRIPTION ACTIVATOR THAT CAN INTERACT WITH P50-NF-KAPPA-B

We have identified a serum-inducible gene, relB, which encodes a protein of 558 amino acids containing a region with high similarity to c-Rel and other members of the Rel family. Transcriptional activation analysis of GAL4-RelB fusion proteins in yeast cells reveals that RelB contains in its C-terminal 180 amino acids a transcriptional activation domain. The N-terminal part including the region of similarity with the Rel family shows no detectable transcriptional activity. RelB does not bind with high affinity to NF-kappa-B sites, but heterodimers between RelB and p50-NF-kappa-B do bind to different NF-kappa-B-binding sites with a similar affinity to that shown by p50-NF-kappa-B homodimers. However, RelB/p50-NF-kappa-B heterodimers, in contrast to p50-NF-kappa-B homodimers, transactivate transcription of a promoter containing a kappa-B-binding site.