N-terminal DNA-binding domains contribute to differential DNA-binding specificities of NF-kappa B p50 and p65.

We previously reported that either oxidation or alkylation of NF-kappa B in vitro abrogates DNA binding. We used this phenomenon to help elucidate structural determinants of NF-kappa B binding. We now demonstrate that Cys-62 of NF-kappa B p50 mediates the redox effect and lies within an N-terminal region required for DNA binding but not for dimerization. Several point mutations in this region confer a transdominant negative binding phenotype to p50. The region is highly conserved in all Rel family proteins, and we have determined that it is also critical for DNA binding of NF-kappa B p65. Replacement of the N-terminal region of p65 with the corresponding region from p50 changes its DNA-binding specificity towards that of p50. These data suggest that the N-terminal regions of p50 and p65 are critical for DNA binding and help determine the DNA-binding specificities of p50 and p65. We have defined within the N-terminal region a sequence motif, R(F/G)(R/K)YXCE, which is present in Rel family proteins and also in zinc finger proteins capable of binding to kappa B sites. The potential significance of this finding is discussed.     

Expression of LMP1 in epithelial cells leads to the activation of a select subset of NF-kappa B/Rel family proteins.

This study demonstrates that the Epstein-Barr virus protein LMP1 activates a specific subset of NF-kappa B/Rel proteins in the C33 epithelial cell line. Western immunoblot analysis used to analyze the intracellular distribution and abundance of the proteins present in these complexes demonstrated that levels of the p50 and p52 proteins were significantly elevated in the nuclei of LMP1-expressing cells. The data also suggest that LMP1 facilitates the translocation of p50 to the nucleus and may affect the processing of the p100 and p105 precursor proteins or the stability of p52 and p50.