Transcription Factor E2F Is Required for Efficient Expression of the Hamster Dihydrofolate Reductase Gene In Vitro and In Vivo

The dihydrofolate reductase (DHFR) gene encodes an enzyme important for metabolism and cell growth. We have found multiple DNA-protein interactions within the hamster DHFR gene promoter in vitro. These interactions occur over the consensus binding sites for two eucaryotic transcription factors. Sp1 and E2F. The DHFR E2F consensus site possesses a dyad symmetry and is unique in its location immediately 3' to the major transcription start site. The interaction of E2F with the DHFR promoter has been detected in HeLa nuclear extracts, confirmed by using partially purified E2F, and characterized by both enzymatic and chemical assays of the DNA-protein interaction. A mutation of the E2F recognition sequence which abolishes E2F binding to the DHFR promoter results in a two- to fivefold decrease of in vitro transcriptional activity and a fivefold reduction of DHFR promoter activity in transient-expression assays. Thus, the interaction of E2F with the DHFR promoter is required for efficient expression of the DHFR gene.