NF-κB2 is a putative target gene of activated notch-1 via RBP-Jκ

NF-kappa B2 (p100/p52), a member of the NF-kappa B/Rel family of transcription factors, is involved in the regulation of a variety of genes important for immune function. Previously, we have shown that the NF-kappa B2 gene is regulated in a positive and a negative manner, Two kappa B elements within the NF-kappa B2 promoter mediate tumor necrosis factor alpha-inducible transactivation. In addition, we have shown that there exists a transcriptional repression in the absence of NF-kappa B. To identify a DNA binding activity responsible for this transcriptional repression, we have partially purified a nuclear complex, named Rep-kappa B, Here we further analyze this putative repressive binding activity. Detailed examination of Rep-kappa B-DNA interaction revealed the sequence requirements for binding to be almost identical to those of recombination signal binding protein J kappa (RBP-J kappa), the mammalian homolog of the protein encoded by Drosophila suppressor of hairless [Su(H)]. In addition, in electromobility shift assays, Rep-kappa B binding activity is recognized by an antibody directed against RBP-J kappa. By performing transient-transfection assays, we show that human RBP-J kappa represses basal as well as RelA (p65)-stimulated NF-kappa B2 promoter activity, Studies in Drosophila melanogaster have shown that Su(H) is implicated in the Notch signaling path,vay regulating cell fate decisions, In transient-transfection assays we show that truncated Notch-1 strongly induces NF-kappa B2 promoter activity. In summary, our data clearly demonstrate that Rep-kappa B is closely related or identical to RBP-J kappa, RBP-J kappa is a strong transcriptional repressor of NF-kappa B2, Moreover, this repression can be overcome by activated Notch-1, suggesting that NF-kappa B2 is a novel putative Notch target gene.