Researchers have uncovered a mechanism by which mitochondria, essential organelles within cells that create energy, cope with an overload of imported proteins. These organelles play a critical role in supporting cell health, producing energy and sustaining many essential biological molecules, such as iron sulfur clusters and heme. However, despite retaining their own DNA, mitochondria must still import many proteins encoded by the cell's nuclear DNA from the surrounding cytoplasm. An outstanding question is how mitochondria cope when their import machinery is overwhelmed with a high volume of proteins or perhaps damaged proteins. Hilla Weidberg and Angelika Amon explored this question by inducing excessive expression of nuclear-encoded mitochondrial proteins within yeast cells and analyzing the response of their mitochondria. They found that, upon mitochondrial import stress, cells mounted a response known as the mitoCPR. This response begins with the expression of PDR3, which in turn increases expression of two additional genes that facilitate the clearing of excess proteins, the authors report. Whether a mitochondrial import stress response exists in higher eukaryotes, like humans, remains to be determined, they say.