Transcription factor Sp1 recognizes a DNA sequence in the mouse dihydrofolate reductase promoter.

Human (HeLa) cells contain a host-cell-encoded transcription factor, Sp1, which is required for transcription of simian virus 40 (SV40) promoters. Since the discovery of Sp1 we have been interested in learning what role this factor plays in uninfected cells. A monkey cellular gene promoter interacts with Sp1, but no gene products linked to this promoter have yet been identified. The finding that the sequence of the 5'-flanking DNA of the mouse dihydrofolate reductase (DHFR) gene contains several regions showing strong homology to the Sp1 binding region of simian virus 40 (SV40) prompted us to undertake experiments with dhfr. We report here that Sp1 binds to these regions in the dhfr promoter, and that Sp1-containing preparations stimulate transcription from the dhfr promoter in an in vitro reaction. Our results suggest that in addition to its interactions with the SV40 viral promoter, one function of Sp1 is to direct the expression of the cellular DHFR gene.