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Cell Metab. 2006 Mar;3(3):199-210.

Functions of mitochondrial ISCU and cytosolic ISCU in mammalian iron-sulfur cluster biogenesis and iron homeostasis.

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National Institute of Child Health and Human Development, Cell Biology and Metabolism Branch, Bethesda, Maryland 20892, USA.


Iron-sulfur (Fe-S) clusters are required for the functions of mitochondrial aconitase, mammalian iron regulatory protein 1, and many other proteins in multiple subcellular compartments. Recent studies in Saccharomyces cerevisiae indicated that Fe-S cluster biogenesis also has an important role in mitochondrial iron homeostasis. Here we report the functional analysis of the mitochondrial and cytosolic isoforms of the human Fe-S cluster scaffold protein, ISCU. Suppression of human ISCU by RNAi not only inactivated mitochondrial and cytosolic aconitases in a compartment-specific manner but also inappropriately activated the iron regulatory proteins and disrupted intracellular iron homeostasis. Furthermore, endogenous ISCU levels were suppressed by iron deprivation. These results provide evidence for a coordinated response to iron deficiency that includes activation of iron uptake, redistribution of intracellular iron, and decreased utilization of iron in Fe-S proteins.

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