title: E2F4 actively promotes the initiation and maintenance of nerve growth factor-induced cell differentiation.
abstract: E2F transcription factors play a critical role in cell cycle progression through the regulation of genes required for G(1)/S transition. They are also thought to be important for growth arrest; however, their potential role in the cell differentiation process has not been previously examined. Here, we demonstrate that E2F4 is highly upregulated following the neuronal differentiation of PC12 cells with nerve growth factor (NGF), while E2F1, E2F3, and E2F5 are downregulated. Immunoprecipitation and subcellular fractionation studies demonstrated that both the nuclear localization of E2F4 and its association with the Rb family member p130 increased following neuronal differentiation. The forced expression of E2F4 markedly enhanced the rate of PC12 cell differentiation induced by NGF and also greatly lowered the rate at which cells lost their neuronal phenotype following NGF removal. Importantly, this effect occurred in the absence of any significant change in the growth regulation of PC12 cells by NGF. Further, the downregulation of E2F4 expression with antisense oligodeoxynucleotides inhibited NGF-induced neurite outgrowth, indicating an important role for this factor during PC12 cell differentiation. Finally, E2F4 expression was found to increase dramatically in the developing rat cerebral cortex and cerebellum, as neuroblasts became postmitotic and initiated terminal differentiation. These findings demonstrate that, in addition to its effects on cell proliferation, E2F4 actively promotes the neuronal differentiation of PC12 cells as well as the retention of this state. Further, this effect is independent of alterations in cell growth and may involve interactions between E2F4 and the neuronal differentiation program itself. E2F4 may be an important participant in the terminal differentiation of neuroblasts.
authors.affiliation: Department of Cellular and Molecular Physiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA.
authors.forename: S P
authors.initials: SP
authors.lastname: Persengiev
authors.forename: I I
authors.initials: II
authors.lastname: Kondova
authors.forename: D L
authors.initials: DL
authors.lastname: Kilpatrick
mesh_terms: D000818:Animals; D001483:Base Sequence; D002454:Cell Differentiation / Q000187:drug effects* / Q000502:physiology*; D002455:Cell Division; D002467:Cell Nucleus / Q000378:metabolism; D002490:Central Nervous System / Q000254:growth & development / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D050704:E2F4 Transcription Factor; D009414:Nerve Growth Factors / Q000494:pharmacology*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D020319:Oligodeoxyribonucleotides, Antisense / Q000235:genetics; D016716:PC12 Cells; D010750:Phosphoproteins / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000187:drug effects; D011506:Proteins; D051381:Rats; D016160:Retinoblastoma Protein / Q000378:metabolism; D050717:Retinoblastoma-Like Protein p130; D013752:Tetracycline / Q000494:pharmacology; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D004268:DNA-Binding Proteins; D050704:E2F4 Transcription Factor; D009414:Nerve Growth Factors; D020319:Oligodeoxyribonucleotides, Antisense; D010750:Phosphoproteins; D011506:Proteins; C493839:Rbl2 protein, rat; D016160:Retinoblastoma Protein; D050717:Retinoblastoma-Like Protein p130; D014157:Transcription Factors; D013752:Tetracycline