'E-boxes' as promoter elements in B cell lines and untransformed B lymphocytes.

The penta-deca (pd) promoter element from the SP6 kappa promoter and the muE2 box from the Ig heavy chain intron enhancer were analysed in an electrophoretic mobility shift assay (EMSA), utilising cell extracts from total mouse splenic B cells before and after stimulation with lipopolysaccharide. With both probes a changed EMSA pattern was observed after stimulation of the cells, where higher molecular weight DNA/protein complexes became dominant. When the pd and muE2 sequence elements were cloned in front of a TATA box and analysed for their transcriptional promoting activity in lipopolysaccharide stimulated B cells, they were inactive. On the contrary, the same constructs were transcriptionally active in some but not all B cell lines. Thus, E-boxes display functional heterogeneity as transcriptional activators depending on host cell.