Apn1 AP-endonuclease is essential for the repair of oxidatively damaged DNA bases in yeast frataxin-deficient cells
Résumé
Frataxin deficiency results in mitochondrial dysfunction and oxidative stress and it is the cause of the hereditary neurodegenerative disease Friedreich ataxia (FA). Here, we present evidence that one of the pleiotrop-ic effects of oxidative stress in frataxin-deficient yeast cells (Dyfh1 mutant) is damage to nuclear DNA and that repair requires the Apn1 AP-endonuclease of the base excision repair pathway. Major phenotypes of Dyfh1 cells are respiratory deficit, disturbed iron homeostasis and sensitivity to oxidants. These phenotypes are weak or absent under anaerobiosis. We show here that exposure of anaerobically grown Dyfh1 cells to oxygen leads to down-regulation of antioxidant defenses, increase in reactive oxygen species, delay in G1-and S-phases of the cell cycle and damage to mitochondrial and nuclear DNA. Nuclear DNA lesions in Dyfh1 cells are primarily caused by oxidized bases and single-strand breaks that can be detected 15-30 min after oxygen exposition. The Apn1 enzyme is essential for the repair of the DNA lesions in Dyfh1 cells. Compared with Dyfh1, the double Dyfh1Dapn1 mutant shows growth impairment, increased mu-tagenesis and extreme sensitivity to H 2 O 2. On the contrary, overexpression of the APN1 gene in Dyfh1 cells decreases spontaneous and induced mutagenesis. Our results show that frataxin deficiency in yeast cells leads to increased DNA base oxidation and requirement of Apn1 for repair, suggesting that DNA damage and repair could be important features in FA disease progression.
Origine : Publication financée par une institution
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