Ace1 prevents intracellular copper accumulation by regulating Fet3 expression and thereby restricting Aft1 activity

In the yeast Saccharomyces cerevisiae Aft1, the low iron‐sensing transcription factor is known to regulate the expression of the FET 3 gene. However, we found that a strain‐lacking FET 3 is more sensitive to copper excess than a strain‐lacking AFT 1 , and accordingly, FET 3 expression is not fully compromised in the latter. These findings suggest that, under such conditions, another regulator comes into play and controls FET 3 expression. In this work, we identify Ace1, the regulator of copper detoxification genes, as a regulator of FET 3 . We suggest that the activation of FET 3 by Ace1 prevents the hyper activation of Aft1, possibly by assuring the adequate functioning of mitochondrial iron–sulfur cluster biogenesis. While reinforcing the link between iron and copper homeostasis, this work unveils a novel protection mechanism against copper toxicity mediated by Ace1, which relies in the activation of FET 3 and results in the restriction of Aft1 activity as a means to prevent excessive copper accumulation.