The DNA repair complex Ku70/86 modulates Apaf1 expression upon DNA damage.
Apaf1 is a key regulator of the mitochondrial intrinsic pathway of apoptosis, as it activates executioner caspases by forming the apoptotic machinery apoptosome. Its genetic regulation and its post-translational modification are crucial under the various conditions where apoptosis occurs. Here we describe Ku70/86, a mediator of non-homologous end-joining pathway of DNA repair, as a novel regulator of Apaf1 transcription. Through analysing different Apaf1 promoter mutants, we identified an element repressing the Apaf1 promoter. We demonstrated that Ku70/86 is a nuclear factor able to bind this repressing element and downregulating Apaf1 transcription. We also found that Ku70/86 interaction with Apaf1 promoter is dynamically modulated upon DNA damage. The effect of this binding is a downregulation of Apaf1 expression immediately following the damage to DNA; conversely, we observed Apaf1 upregulation and apoptosis activation when Ku70/86 unleashes the Apaf1-repressing element. Therefore, besides regulating DNA repair, our results suggest that Ku70/86 binds to the Apaf1 promoter and represses its activity. This may help to inhibit the apoptosome pathway of cell death and contribute to regulate cell survival.
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Department of Biology, Dulbecco Telethon Institute, University of Rome Tor Vergata, 00133 Rome, Italy.
Bordi
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Ferraro
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Ciccosanti
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Fimia
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Orlando
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D000818:Animals; D034961:Antigens, Nuclear / Q000737:chemistry / Q000378:metabolism*; D053477:Apoptotic Protease-Activating Factor 1 / Q000235:genetics*; D016923:Cell Death / Q000187:drug effects; D002460:Cell Line; D004249:DNA Damage / Q000235:genetics; D004260:DNA Repair / Q000187:drug effects / Q000235:genetics; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D005047:Etoposide / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D000072200:Ku Autoantigen; D051379:Mice; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D012097:Repressor Proteins / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014158:Transcription, Genetic / Q000187:drug effects
D034961:Antigens, Nuclear; C506593:Apaf1 protein, mouse; D053477:Apoptotic Protease-Activating Factor 1; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D005047:Etoposide; D006861:Hydrogen Peroxide; C000606509:Xrcc6 protein, human; C000606510:Xrcc6 protein, mouse; D000072200:Ku Autoantigen