title: Targeting an E2F site in the mouse genome prevents promoter silencing in quiescent and post-mitotic cells.
abstract: Previous studies have shown that the cell cycle-regulated B-myb promoter contains a conserved E2F binding site that is critical for repressing transcription in quiescent cells. To investigate its significance for permanent promoter silencing, we have inactivated this binding site in the mouse genome. Mice homozygous for the mutant B-mybmE2F allele were fully viable, however, B-myb transcription was derepressed during quiescence in mouse embryo fibroblasts (MEFs) derived from mutant animals. Moreover, it was found that mutation of the E2F site resulted in abnormal maintenance of B-myb expression in senescent MEFs and in differentiated brain tissue. These findings therefore reveal a direct and primary role for repressive E2F complexes in silencing gene expression in post-mitotic cells. Analysis of histone modifications at the promoter showed that histone H3 lysine 9 was constitutively acetylated throughout the cell cycle in homozygous mutant MEFs. This mouse system is the first description of an E2F site mutation in situ and will facilitate the study of E2F function in vivo.
authors.affiliation: Department of Virology, Faculty of Medicine, Imperial College London, London, UK.
authors.forename: F
authors.initials: F
authors.lastname: Tavner
authors.forename: J
authors.initials: J
authors.lastname: Frampton
authors.forename: R J
authors.initials: RJ
authors.lastname: Watson
mesh_terms: D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000235:genetics / Q000502:physiology*; D002478:Cells, Cultured; D047369:Chromatin Immunoprecipitation; D018983:DNA Footprinting; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D050684:E2F Transcription Factors / Q000235:genetics / Q000378:metabolism*; D004622:Embryo, Mammalian; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D020868:Gene Silencing; D051379:Mice; D018345:Mice, Knockout; D008938:Mitosis; D009154:Mutation / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; C499306:Mybl2 protein, mouse; D012333:RNA, Messenger; D015534:Trans-Activators