NF-κB Subunit Regulation in Nontransformed CD4 + T Lymphocytes

Regulation of interleukin-2 (IL-2) gene expression by the p50 and p65 subunits of the DNA binding protein NF-kappa B was studied in nontransformed CD4+ T lymphocyte clones. A homodimeric complex of the NF-kappa B p50 subunit was found in resting T cells. The amount of p50-p50 complex decreased after full antigenic stimulation, whereas the amount of the NF-kappa B p50-p65 heterodimer was increased. Increased expression of the IL-2 gene and activity of the IL-2 kappa B DNA binding site correlated with a decrease in the p50-p50 complex. Overexpression of p50 repressed IL-2 promoter expression. The switch from p50-p50 to p50-p65 complexes depended on a protein that caused sequestration of the p50-p50 complex in the nucleus.