A major conclusion of this work is that Yfh1 deficiency activates the iron regulon by a different pathway than iron-sulfur loss. Therefore, alternative pathways for Aft1 activation may exist in yeast which, as discussed above, could be related to the presence of anomalous iron species. We have also observed that metabolic status can be efficiently monitored using a targeted proteomics strategy focusing on key metabolic enzymes. Finally, the observation that NO can mitigate the defects caused by Yfh1 deficiency supports the hypothesis that Yfh1 loss leads to the increased presence of anomalous iron forms, and that this anomalous iron plays a central role in the events caused by Yfh1 deficiency. It also suggests that NO donors could have a therapeutic effect in FRDA patients. NO donors such as SNP or nitroglycerin have been used for more than a century for controlling congestive heart failure associated with heart attack or lowering blood pressure during surgery. Beyond its vasodilating action, neuroprotective properties have been demonstrated for NO in an iron-induced model of Parkinson's disease. This observation, together with the results presented in this work, opens the possibility to explore the potential therapeutic effect of NO donors in mammalian models of FRDA.
