Frataxin knockdown causes loss of cytoplasmic iron-sulfur cluster functions, redox alterations and induction of heme transcripts

Arch Biochem Biophys. 2007 Jan 1;457(1):111-22. doi: 10.1016/ Epub 2006 Oct 4.


Frataxin protein deficiency causes the neurodegenerative disease Friedreich ataxia. We used inducible siRNA to order the consequences of frataxin deficiency that we and others have previously observed. The earliest consequence of frataxin deficiency was a defect in cytoplasmic iron-sulfur proteins. In the second phase, protein oxidative damage increased, and CuZnSOD was induced, as was the unfolded protein response (UPR), long before any decline in mitochondrial aconitase activity. In the third phase, mitochondrial aconitase activity declined. And in the fourth phase, coincident with the decrease in heme-containing cytochrome c protein, a transcriptional induction of the heme-dependent transcripts ALAS1 and MAOA occurred. These observations suggest that the earliest consequences of frataxin deficiency occur in ISC proteins of the cytoplasm, resulting in oxidative damage and stress and activation of the unfolded protein response which has been associated with neurological disease, and that later consequences involve mitochondrial iron-sulfur cluster deficiency, heme deficiency, and then increased heme biosynthesis.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Cell Line
  • Cytochromes c / metabolism
  • Cytoplasm / metabolism
  • Gene Expression
  • Heme / biosynthesis*
  • Humans
  • Iron-Binding Proteins / genetics
  • Iron-Binding Proteins / physiology*
  • Iron-Sulfur Proteins / metabolism*
  • Mitochondrial Proteins / genetics
  • Mitochondrial Proteins / physiology
  • Oxidative Stress*
  • Protein Folding
  • RNA, Small Interfering / genetics
  • Signal Transduction
  • Superoxide Dismutase / metabolism


  • Iron-Binding Proteins
  • Iron-Sulfur Proteins
  • Mitochondrial Proteins
  • RNA, Small Interfering
  • frataxin
  • Heme
  • Cytochromes c
  • Superoxide Dismutase