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.
Department of Biology, Dulbecco Telethon Institute, University of Rome Tor Vergata, 00133 Rome, Italy.
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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