Apaf-1 is a mediator of E2F-1-induced apoptosis.
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.
Furukawa
Yusuke
Y
Division of Stem Cell Regulation, Center for Molecular Medicine and the Department of Biochemistry, Jichi Medical School, Tochigi 329-0498, Japan. furuyu@jichi.ac.jp
Nishimura
Noriko
N
Furukawa
Yutaka
Y
Satoh
Masaaki
M
Endo
Hitoshi
H
Iwase
Satsuki
S
Yamada
Hisashi
H
Matsuda
Michio
M
Kano
Yasuhiko
Y
Nakamura
Mitsuru
M
D017209:Apoptosis; D053477:Apoptotic Protease-Activating Factor 1; D001483:Base Sequence; D001665:Binding Sites; D015152:Blotting, Northern; D053148:Caspase 3; D053178:Caspase 6; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D018797:Cell Cycle Proteins; D002460:Cell Line; D002843:Chromatin / Q000378:metabolism; D018899:CpG Islands; D003600:Cytosol / Q000378:metabolism; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D004789:Enzyme Activation; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D006801:Humans; D015151:Immunoblotting; D020014:K562 Cells; D008564:Membrane Potentials; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000378:metabolism; D008969:Molecular Sequence Data; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism* / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D015854:Up-Regulation; D051028:bcl-2-Associated X Protein
C506592:APAF1 protein, human; D053477:Apoptotic Protease-Activating Factor 1; D018797:Cell Cycle Proteins; D002843:Chromatin; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D011506:Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; C505407:CASP3 protein, human; C505514:CASP6 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053178:Caspase 6; D053453:Caspase 9; D020169:Caspases