DISTINCT NF-KAPPA-B REL TRANSCRIPTION FACTORS ARE RESPONSIBLE FOR TISSUE-SPECIFIC AND INDUCIBLE GENE ACTIVATION

THE NF-kappaB/Rel family is a growing class of transcriptional regulat ors1-11 whose members share the conserved Rel-homology domain, involve d in specific DNA binding and dimerization. They interact with the reg ulatory elements of many different genes and are involved in the regul ation of lymphoid-specific and inducible transcription12. We tested wh ether these factors could alone activate a gene in transgenic mice. We report here that a minimal promoter containing three copies of a bind ing site for these proteins allows tissue-specific and inducible trans gene activation. In lymphoid tissues constitutive transgene expression correlates with the presence of a constitutively active p50/RelB hete rodimer. Other organs that only contain the p50 homodimer do not expre ss the transgene. In contrast to this constitutive activity mediated b y p50/RelB, the p50/p65 heterodimer (which is NF-kappaB) could confer inducible transgene activation in embryo fibroblasts. Thus two differe nt members of the NF-kappaB/Rel family of transcriptional activators a re involved in tissue-specific and inducible gene activation in transg enic mice.