Identification of Dβ1 promoter sequences binding nuclear proteins in T and B cells. Overlapping double-stranded oligonucleotide probes spanning -350 to +150 were labeled and incubated with either no extract, p5424, or A20 nuclear extracts, as indicated, and were analyzed by EMSA on nondenaturing polyacrylamide gels. Results from probes centered at -35, -281, and -314 relative to Dβ1 are presented.