Frataxin gene of Friedreich's ataxia is targeted to mitochondria

Abstract
Friedriech's ataxia is caused by a triplet repeat expanison in intron 1, a noncoding region of the frataxin gene (X25). We have generated a chimeric gene composed of the frataxin gene fused with the green fluorescent protein (GFP) gene as a reporter. Transfection of the fusion construct into living COS cells revealed that the frataxin–GFP construct localizes to organelles that double‐label with 8–(4′‐chloromethyl) phenyl‐2,3,5,6,11,12,14,15‐octahydro‐1H,4H,10H‐13H‐diquinolizino‐8H‐xanthylium chloride (CMXRos), a novel mitochondrial dye. Thus, frataxin appears to be a nuclear‐encoded mitochondrial protein.