Apaf-1 is a mediator of E2F-1-induced apoptosis

J Biol Chem. 2002 Oct 18;277(42):39760-8. doi: 10.1074/jbc.M200805200. Epub 2002 Jul 30.

Abstract

E2F-1 is capable of promoting both cell cycle progression and apoptosis. The latter is important for suppressing untoward expansion of proliferating cells. In this study, we investigated its underlying mechanisms. E2F-1-induced apoptosis was accompanied by caspase-9 activation and inhibited by a specific inhibitor of caspase-9 in K562 sublines overexpressing E2F-1. E2F-1 enhanced the expression of Apaf-1 without the cytosolic accumulation of cytochrome c. Apaf-1-deficient melanoma cell lines were resistant to E2F-1, indicating that Apaf-1 is an essential element of E2F-1-mediated apoptosis. Finally, we isolated the promoter region of the Apaf-1 gene and found a putative binding site for E2F. A chromatin immunoprecipitation assay revealed that E2F-1 bound to Apaf-1 promoter upon E2F-1 overexpression, suggesting that Apaf-1 is under transcriptional regulation of E2F-1. These data demonstrate a novel mechanism of apoptosis in which an increase in Apaf-1 levels results in direct activation of caspase-9 without mitochondrial damage, leading to the initiation of a caspase cascade.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis*
  • Apoptotic Protease-Activating Factor 1
  • Base Sequence
  • Binding Sites
  • Blotting, Northern
  • Caspase 3
  • Caspase 6
  • Caspase 9
  • Caspases / metabolism
  • Cell Cycle Proteins*
  • Cell Line
  • Chromatin / metabolism
  • CpG Islands
  • Cytosol / metabolism
  • DNA-Binding Proteins*
  • E2F Transcription Factors
  • E2F1 Transcription Factor
  • Enzyme Activation
  • Flow Cytometry
  • Gene Expression Regulation
  • Humans
  • Immunoblotting
  • K562 Cells
  • Membrane Potentials
  • Microscopy, Confocal
  • Microscopy, Fluorescence
  • Mitochondria / metabolism
  • Molecular Sequence Data
  • Plasmids / metabolism
  • Precipitin Tests
  • Promoter Regions, Genetic
  • Protein Binding
  • Proteins / metabolism*
  • Proteins / physiology*
  • Proto-Oncogene Proteins / metabolism
  • Proto-Oncogene Proteins c-bcl-2*
  • Time Factors
  • Transcription Factors / metabolism*
  • Transcription, Genetic
  • Transfection
  • Tumor Cells, Cultured
  • Tumor Suppressor Protein p53 / metabolism
  • Up-Regulation
  • bcl-2-Associated X Protein

Substances

  • APAF1 protein, human
  • Apoptotic Protease-Activating Factor 1
  • Cell Cycle Proteins
  • Chromatin
  • DNA-Binding Proteins
  • E2F Transcription Factors
  • E2F1 Transcription Factor
  • E2F1 protein, human
  • Proteins
  • Proto-Oncogene Proteins
  • Proto-Oncogene Proteins c-bcl-2
  • Transcription Factors
  • Tumor Suppressor Protein p53
  • bcl-2-Associated X Protein
  • CASP3 protein, human
  • CASP6 protein, human
  • CASP9 protein, human
  • Caspase 3
  • Caspase 6
  • Caspase 9
  • Caspases