The transcription factor E2F1 promotes dopamine-evoked neuronal apoptosis by a mechanism independent of transcriptional activation.
The E2F1 transcription factor plays an important role in promoting neuronal apoptosis; however, it is not clear how E2F1 does this. Here we show that E2F1 is involved in dopamine (DA)-evoked apoptosis in cerebellar granule neurons (CGNs). E2F1 -/- CGNs and CGNs expressing an antisense E2F1 cDNA were significantly protected from DA-toxicity relative to controls. The neuronal protection was accompanied by significantly reduced caspase 3 activity. E2F1-mediated neuronal apoptosis did not require activation of gene transcription because: (1) ectopic expression of E2F1 or its mutants lacking the transactivation domain induced neuronal apoptosis, whereas an E2F1 mutant lacking the DNA-binding domain did not; (2) under all of these conditions, known E2F1 target genes including cyclin A, cdc2 and p19(ARF) were not induced; and (3) DA-evoked neuronal apoptosis was associated with up-regulated E2F1, but not transcription of its target genes. Finally, E2F1-mediated neuronal apoptosis was associated with reduced nuclear factor (NF)-kappaB DNA-binding activity. Taken together, these data suggest that E2F1 promotes DA-evoked caspase 3-dependent neuronal apoptosis by a mechanism independent of gene transactivation, and this may possibly occur through inhibition of anti-apoptotic genes including NF-kappaB.
Hou
S T
ST
Institute for Biological Sciences, National Research Council Canada, Ottawa, Ontario, Canada. sheng.hou@nrc.ca
Cowan
E
E
Walker
T
T
Ohan
N
N
Dove
M
M
Rasqinha
I
I
MacManus
J P
JP
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D018797:Cell Cycle Proteins; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000502:physiology*; D016373:DNA, Antisense / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism; D004298:Dopamine / Q000633:toxicity*; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins; D006801:Humans; D008156:Luciferases / Q000235:genetics; D008164:Luminescent Proteins / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D009474:Neurons / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D016627:Oxidopamine / Q000633:toxicity; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection
D018797:Cell Cycle Proteins; D016373:DNA, Antisense; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; C493754:E2f1 protein, mouse; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D049452:Green Fluorescent Proteins; D016627:Oxidopamine; D008156:Luciferases; C505407:CASP3 protein, human; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases; D004298:Dopamine