Cell-specific activity of the constituent elements of the simian virus 40 enhancer

We have compared the activation of transcription from the early promoter of simian virus 40 brought about by the enhancer during transient expression in several cell lines. The enhancer stimulated RNA synthesis approximately 400-, 100-, 100-, and 300-fold in human HeLa cells, the mouse plasmacytoma B cells MPC11, and the nondifferentiated and retinoic acid-differentiated mouse embryonal carcinoma F9 cells, respectively. The contribution to enhancer activity of its multiple constituent motifs has been investigated in the different cell types using the pA series of recombinants mutated throughout the enhancer. A comparison of the activity of these recombinants in the four cell lines indicates that the activity of the various enhancer motifs is cell specific. The activity of a given motif in a given cell line correlates well with the known presence in this cell line of a protein(s) that binds specifically to that motif in vitro.