STRUCTURAL AND FUNCTIONAL-ANALYSIS OF NF-KAPPA-B - DETERMINANTS OF DNA-BINDING SPECIFICITY AND PROTEIN-INTERACTION

The NF-kappa B transcription factors display a high degree of sequence conservation in a domain initially described in the rel oncogene. Two family members, NF-kappa B1 and NF-kappa B2, have distinct DNA bindin g properties and functionally distinct effects on different enhancers. NF-kappa B1, for example, binds to the kappa B Site from the human im munodeficiency virus (HIV) with similar to 15-fold higher affinity tha n NF-kappa B2. In this study, we have defined regions within the Rel d omain which determine DNA binding specificity and interaction with oth er proteins. We find that the COOH-terminal putative Rel dimerization domain of NF-kappa B1 is required for preferential binding to the HIV KB site. In contrast, preferential stimulation of the HIV enhancer by NF-kappa B2 with RelA(p65) is determined by both the NH2- and COOH-ter minal Rel domains of NF-kappa B2. These two regions of NF-kappa B2 als o mediate preferential synergy with Bcl3. These data suggest that a sp ecific subdomain of the Rel conserved region has evolved to control th e fine specificity of DNA binding, and two distinct subregions within the Rel domain determine the specificity of interaction with other tra nscription factors. These specific Rel-conserved domains therefore det ermine the specificity of NF-kappa B interactions and contribute to se lective gene activation.