title: Functional roles of E2F in cell cycle regulation.
abstract: The E2F family of transcription factors play a key role in G1-S progression. A dominant negative mutant (E2F97) of E2F1 containing the DNA binding domain of E2F1 under the control of a tetracycline-responsive promoter was constructed. Stable transfectants were produced in the pRb-lacking SaOS-2 cell line and SV40-transformed VA-13 cell line, respectively. Induction of E2F97 by tetracycline withdrawal resulted in strong inhibition of the E2F transcriptional activity and a decreased percentage of cells in S-phase. To understand the mechanism(s) by which E2F97 exerts its effect on the cell cycle, the effect of E2F97 on expression of various cell cycle proteins was examined. Upon induction of E2F97, a significant decrease in the levels of both dihydrofolate reductase and thymidylate synthase was observed in transfectants derived from both cell lines. Induction of E2F97 also led to a decrease in cyclin A and D1 protein levels. Regulation of cyclin A by E2F97 occurred at the transcriptional level. In addition, in VA13 cells, induction of E2F97 resulted in down-regulation of the tumor suppressor protein p53. These data suggest that E2F regulates both G1 and S-phase cyclins and that there may be a potential positive feedback regulatory loop between E2F and cyclin D1.
authors.affiliation: Program for Molecular Pharmacology and Therapeutics, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
authors.forename: J
authors.initials: J
authors.lastname: Fan
authors.forename: J R
authors.initials: JR
authors.lastname: Bertino
mesh_terms: D002352:Carrier Proteins; D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins; D002455:Cell Division / Q000502:physiology; D002461:Cell Line, Transformed; D002472:Cell Transformation, Viral; D016213:Cyclins / Q000096:biosynthesis / Q000187:drug effects / Q000378:metabolism; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D009154:Mutation; D012516:Osteosarcoma / Q000235:genetics / Q000473:pathology; D056465:Retinoblastoma-Binding Protein 1; D016196:S Phase / Q000502:physiology; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D014162:Transfection; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis
chemical_list: D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D016213:Cyclins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53