title: Direct repression of the Mcl-1 promoter by E2F1.
abstract: E2F1 induces apoptosis via both p53-dependent and p53-independent mechanisms. The direct targets in the p53-independent pathway remain enigmatic; however, the induction of this pathway does not require the transactivation domain of E2F1. Using cells that are defective in p53 activation, we show that E2F1 potently represses the expression of Mcl-1--an anti-apoptotic Bcl-2 family member whose depletion results in apoptosis. We also show that this transcriptional repression is direct and dependent upon E2F1's DNA-binding domain, but does not require the transactivation domain of E2F1. Consistent with this DNA binding requirement of E2F1 to repress Mcl-1, we show that E2F1 binds to the Mcl-1 promoter both in vitro and in vivo, and have identified the DNA element (-143/-117) within this promoter that is required for E2F1 binding and repression. Additionally, cell lines constitutively expressing Mcl-1 are resistant to E2F1-mediated apoptosis--suggesting that Mcl-1 downregulation is a necessary event in the p53-independent apoptotic process. Thus, we identify a p53 family-independent mechanism of E2F1-induced apoptosis in which E2F1 directly represses Mcl-1 expression.
authors.affiliation: Molecular Oncology Program, H. Lee Moffitt Comprehensive Cancer Center and Research Institute, University of South Florida, College of Medicine, Tampa, Florida, FL 33612, USA.
authors.forename: Rhonda
authors.initials: R
authors.lastname: Croxton
authors.forename: Yihong
authors.initials: Y
authors.lastname: Ma
authors.forename: Lanxi
authors.initials: L
authors.lastname: Song
authors.forename: Eric B
authors.initials: EB
authors.lastname: Haura
authors.forename: W Douglas
authors.initials: WD
authors.lastname: Cress
mesh_terms: D016475:3T3 Cells; D000818:Animals; D017209:Apoptosis; D001483:Base Sequence; D015153:Blotting, Western; D018797:Cell Cycle Proteins; D002843:Chromatin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016384:Consensus Sequence / Q000235:genetics; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D024202:Electrophoretic Mobility Shift Assay; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic; D017930:Genes, Reporter; D051379:Mice; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000235:genetics* / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic / Q000235:genetics*; D019253:Proto-Oncogene Proteins c-bcl-2; D012097:Repressor Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D020218:Response Elements / Q000235:genetics; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D018797:Cell Cycle Proteins; D002843:Chromatin; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493754:E2f1 protein, mouse; C579094:Mcl1 protein, mouse; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012097:Repressor Proteins; D014157:Transcription Factors