RelB, a new Rel family transcription activator that can interact with p50-NF-kappa B.

Abstract

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-KB sites, but heterodimers between RelB and p50-NF-KB do bind to different NF-KtB-binding sites with a similar affinity to that shown by p50-NF-KB homodimers. However, RelB/p50-NF-KB heterodimers, in contrast to p50-NF-KB homodimers, transactivate transcription of a promoter containing a KB-binding site.Growth factors and other mitogens are capable of rapidly inducing a complex set of more than 100 genes in quiescent fibroblasts (1,13,31,32,38). These genes, which have been named immediate-early or early response genes, are transcriptionally activated within minutes after addition of growth factor or mitogen independently of de novo protein synthesis. Among these genes are several encoding bona fide or putative transcription factors such as members of the fos and jun families, zinc finger proteins (for reviews, see references 8, 22, and 33), or others containing undefined motifs like the Rel domain found in the proto-oncogene c-rel product (11,12,20) and the transcription factor NF-KB (7,16,28,44,47,49,51).The proto-oncogene c-rel (60) is the cellular homolog of the v-rel oncogene (53), isolated from reticuloendotheliosis virus strain T, a turkey-derived acutely transforming retrovirus (56) causing lymphoid leukemia. The c-rellv-rel genes are part of a rapidly growing family of transcription factors. One member of this family is the dorsal gene of Drosophila melanogaster, which is involved in establishing the dorsalventral axis (54) and is able to bind to NF-KB-like DNA sequences (23, 57). The other members are the transcription factor p50-NF-KB (also known as KBF1) with its precursor pl05-NF-KB (7,16,28,44), p50B(p49)-NF-KB with its precursor p97-NF-KB (6a, 51), and p65-NF-KB (47, 49). p50 and p65 form a heterodimer that is able to bind to NF-KB-binding sites found in many enhancers and promoters such as in the immunoglobulin kappa genes, interleukin-2, interleukin-6, ,-interferon, and others (for a review, see reference 35).All the members of the Rel family share a highly conserved domain of approximately 300 amino acids termed the Rel domain, which is considered to function as a DNAbinding and protein dimerization region with properties yet to be defined in detail. Additionally, all the members of this family show a regulated movement from the cytoplasm to the nucleus (for reviews, see references 17 and 36). In particular for the NF-KB complex it is known that p65 is able * Corresponding author.to interact with an inhibitor, IKB, which keeps it in the cytoplasm. After activation of cells, IKB is i...

Rel/NF-κB transcription factors and IκB inhibitors: Evolution from a unique common ancestor

“…cRel, RelA and RelB paralogous genes diverged with similar evolutionary speed, although the RelB gene seems to have slightly accelerated. Despite their highly conserved features, they strikingly di er in their dimerization speci®city since RelB proteins are unable to homodimerize (Dobrzanski et al, 1993;Ruben et al, 1992b;Ryseck et al, 1992;Suzuki et al, 1995). The third group of subfamily I proteins contains Dorsal and Dif which present the RHD-TA organization and bind DNA as homodimers only.…”

RelB regulates manganese superoxide dismutase gene and resistance to ionizing radiation of prostate cancer cells

“…Upon cell stimulation, p100 is degraded resulting in the release of RelB and p52. RelB dimerizes with either p50 or p52 and translocates to the nucleus to transactivate genes (Ryseck et al, 1992). To further elucidate the direct role of RelB in radiation response, RelB function was inhibited by two different approaches, a dominant negative form of p100 and RelBspecific siRNA.…”

Transcriptional elongation of c-myb is regulated by NF-κB (p50/RelB)

“…The cDNAs encoding p50 and relB (Mercurio et al, 1993;Ryseck et al, 1992) were subcloned into vectors allowing expression from the chicken b-actin promoter; the p50 and relB expression vectors contained an expression cassette for the neomycin and hygromycin resistance gene, respectively. The reporter plasmids pNFkB-Luc, pNFkB(mut)-Luc, p(7453/ +80)HIV-Luc, pDNFkB(7453/+80)HIV-Luc and pAP1-Luc were generously provided by M Karin (Devary et al, 1993).…”