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Protein FXN PDB 1ekg.png
Available structures
PDBOrtholog search: PDBe RCSB
AliasesFXN, CyaY, FA, FARR, FRDA, X25, frataxin
External IDsOMIM: 606829 MGI: 1096879 HomoloGene: 47908 GeneCards: FXN
Gene location (Human)
Chromosome 9 (human)
Chr.Chromosome 9 (human)[1]
Chromosome 9 (human)
Genomic location for FXN
Genomic location for FXN
Band9q21.11Start69,035,259 bp[1]
End69,120,427 bp[1]
RNA expression pattern
PBB GE FXN 205565 s at fs.png
More reference expression data
RefSeq (mRNA)



RefSeq (protein)



Location (UCSC)Chr 9: 69.04 – 69.12 MbChr 19: 24.26 – 24.28 Mb
PubMed search[3][4]
View/Edit HumanView/Edit Mouse

Frataxin is a protein that in humans is encoded by the FXN gene.[5][6]


Frataxin is localized to the mitochondrion. The function of frataxin is not entirely clear, but it seems to be involved in assembly of iron-sulfur clusters. It has been proposed to act as either an iron chaperone or an iron storage protein.[7]

Frataxin mRNA is predominantly expressed in tissues with a high metabolic rate (including liver, kidney, brown fat and heart). Mouse and yeast frataxin homologues contain a potential N-terminal mitochondrial targeting sequence, and human frataxin has been observed to co-localise with a mitochondrial protein. Furthermore, disruption of the yeast gene has been shown to result in mitochondrial dysfunction. Friedreich's ataxia is thus believed to be a mitochondrial disease caused by a mutation in the nuclear genome (specifically, expansion of an intronic GAA triplet repeat in the FXN gene, which encodes the protein frataxin.).[5][8][9]

Clinical significance[edit]

Reduced expression of frataxin is the cause of Friedreich's ataxia (FRDA), a lethal neurodegenerative disease. The reduction in frataxin gene expression may be attributable from either the silencing of transcription of the frataxin gene because of epigenetic modifications in the chromosomal entity[10] or from the inability of splicing the expanded GAA repeats in the first intron of the pre-mRNA as seen in Bacteria[11] and Human cells[12] or both. The expansion of intronic trinucleotide repeat GAA results in Friedreich's ataxia.[13] This expanded repeat causes R-loop formation, and using a repeat-targeted oligonucleotide to disrupt the R-loop can reactivate frataxin expression.[14]

Animal studies[edit]

An overexpression of frataxin in Drosophila has shown an increase in antioxidant capability, resistance to oxidative stress insults and longevity.[15]

Fibroblasts from a mouse model of Friedreich’s ataxia and Friedreich’s ataxia patient fibroblasts show increased levels of DNA double-strand breaks.[16] A lentivirus gene delivery system was used to deliver the frataxin gene to the Friedreich’s ataxia mouse model and human patient cells, and this resulted in long-term restored expression of frataxin mRNA and frataxin protein. This restored expression of the frataxin gene was accompanied by a substantial reduction in the number of DNA double-strand breaks.[16] The impaired frataxin in Friedreich’s ataxia cells appears to cause reduced capacity for repair of DNA damage and this may contribute to neurodegeneration.[16]


Frataxin has been shown to biologically interact with the enzyme PMPCB.[17]


  1. ^ a b c GRCh38: Ensembl release 89: ENSG00000165060 - Ensembl, May 2017
  2. ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000059363 - Ensembl, May 2017
  3. ^ "Human PubMed Reference:".
  4. ^ "Mouse PubMed Reference:".
  5. ^ a b Campuzano V, Montermini L, Moltò MD, Pianese L, Cossée M, Cavalcanti F, Monros E, Rodius F, Duclos F, Monticelli A, Zara F, Cañizares J, Koutnikova H, Bidichandani SI, Gellera C, Brice A, Trouillas P, De Michele G, Filla A, De Frutos R, Palau F, Patel PI, Di Donato S, Mandel JL, Cocozza S, Koenig M, Pandolfo M (Mar 1996). "Friedreich's ataxia: autosomal recessive disease caused by an intronic GAA triplet repeat expansion". Science. 271 (5254): 1423–7. doi:10.1126/science.271.5254.1423. PMID 8596916.
  6. ^ Carvajal JJ, Pook MA, dos Santos M, Doudney K, Hillermann R, Minogue S, Williamson R, Hsuan JJ, Chamberlain S (Oct 1996). "The Friedreich's ataxia gene encodes a novel phosphatidylinositol-4- phosphate 5-kinase". Nature Genetics. 14 (2): 157–62. doi:10.1038/ng1096-157. PMID 8841185.
  7. ^ Adinolfi S, Iannuzzi C, Prischi F, Pastore C, Iametti S, Martin SR, Bonomi F, Pastore A (Apr 2009). "Bacterial frataxin CyaY is the gatekeeper of iron-sulfur cluster formation catalyzed by IscS". Nature Structural & Molecular Biology. 16 (4): 390–6. doi:10.1038/nsmb.1579. PMID 19305405.
  8. ^ Dürr A, Cossee M, Agid Y, Campuzano V, Mignard C, Penet C, Mandel JL, Brice A, Koenig M (Oct 1996). "Clinical and genetic abnormalities in patients with Friedreich's ataxia". The New England Journal of Medicine. 335 (16): 1169–75. doi:10.1056/NEJM199610173351601. PMID 8815938.
  9. ^ Koutnikova H, Campuzano V, Foury F, Dollé P, Cazzalini O, Koenig M (Aug 1997). "Studies of human, mouse and yeast homologues indicate a mitochondrial function for frataxin". Nature Genetics. 16 (4): 345–51. doi:10.1038/ng0897-345. PMID 9241270.
  10. ^ Kim E, Napierala M, Dent SY (Oct 2011). "Hyperexpansion of GAA repeats affects post-initiation steps of FXN transcription in Friedreich's ataxia". Nucleic Acids Research. 39 (19): 8366–77. doi:10.1093/nar/gkr542. PMC 3201871. PMID 21745819.
  11. ^ Pan X, Ding Y, Shi L (Nov 2009). "The roles of SbcCD and RNaseE in the transcription of GAA x TTC repeats in Escherichia coli". DNA Repair. 8 (11): 1321–7. doi:10.1016/j.dnarep.2009.08.001. PMID 19733517.
  12. ^ Baralle M, Pastor T, Bussani E, Pagani F (Jul 2008). "Influence of Friedreich ataxia GAA noncoding repeat expansions on pre-mRNA processing". American Journal of Human Genetics. 83 (1): 77–88. doi:10.1016/j.ajhg.2008.06.018. PMC 2443835. PMID 18597733.
  13. ^ "Entrez Gene: FXN frataxin".
  14. ^ Li L, Matsui M, Corey DR (2016-01-01). "Activating frataxin expression by repeat-targeted nucleic acids". Nature Communications. 7: 10606. doi:10.1038/ncomms10606. PMC 4742999. PMID 26842135.
  15. ^ Runko AP, Griswold AJ, Min KT (Mar 2008). "Overexpression of frataxin in the mitochondria increases resistance to oxidative stress and extends lifespan in Drosophila". FEBS Letters. 582 (5): 715–9. doi:10.1016/j.febslet.2008.01.046. PMID 18258192.
  16. ^ a b c Khonsari H, Schneider M, Al-Mahdawi S, Chianea YG, Themis M, Parris C, Pook MA, Themis M (December 2016). "Lentivirus-meditated frataxin gene delivery reverses genome instability in Friedreich ataxia patient and mouse model fibroblasts". Gene Ther. 23 (12): 846–856. doi:10.1038/gt.2016.61. PMC 5143368. PMID 27518705.
  17. ^ Koutnikova H, Campuzano V, Koenig M (Sep 1998). "Maturation of wild-type and mutated frataxin by the mitochondrial processing peptidase". Human Molecular Genetics. 7 (9): 1485–9. doi:10.1093/hmg/7.9.1485. PMID 9700204.

Further reading[edit]

  • Thierbach R, Drewes G, Fusser M, Voigt A, Kuhlow D, Blume U, Schulz TJ, Reiche C, Glatt H, Epe B, Steinberg P, Ristow M (Nov 2010). "The Friedreich's ataxia protein frataxin modulates DNA base excision repair in prokaryotes and mammals". The Biochemical Journal. 432 (1): 165–72. doi:10.1042/BJ20101116. PMC 2976068. PMID 20819074.
  • Montermini L, Rodius F, Pianese L, Moltò MD, Cossée M, Campuzano V, Cavalcanti F, Monticelli A, Palau F, Gyapay G (Nov 1995). "The Friedreich ataxia critical region spans a 150-kb interval on chromosome 9q13". American Journal of Human Genetics. 57 (5): 1061–7. PMC 1801369. PMID 7485155.
  • Bidichandani SI, Ashizawa T, Patel PI (May 1997). "Atypical Friedreich ataxia caused by compound heterozygosity for a novel missense mutation and the GAA triplet-repeat expansion". American Journal of Human Genetics. 60 (5): 1251–6. PMC 1712428. PMID 9150176.
  • Babcock M, de Silva D, Oaks R, Davis-Kaplan S, Jiralerspong S, Montermini L, Pandolfo M, Kaplan J (Jun 1997). "Regulation of mitochondrial iron accumulation by Yfh1p, a putative homolog of frataxin". Science. 276 (5319): 1709–12. doi:10.1126/science.276.5319.1709. PMID 9180083.
  • Koutnikova H, Campuzano V, Foury F, Dollé P, Cazzalini O, Koenig M (Aug 1997). "Studies of human, mouse and yeast homologues indicate a mitochondrial function for frataxin". Nature Genetics. 16 (4): 345–51. doi:10.1038/ng0897-345. PMID 9241270.
  • Wilson RB, Roof DM (Aug 1997). "Respiratory deficiency due to loss of mitochondrial DNA in yeast lacking the frataxin homologue". Nature Genetics. 16 (4): 352–7. doi:10.1038/ng0897-352. PMID 9241271.
  • Campuzano V, Montermini L, Lutz Y, Cova L, Hindelang C, Jiralerspong S, Trottier Y, Kish SJ, Faucheux B, Trouillas P, Authier FJ, Dürr A, Mandel JL, Vescovi A, Pandolfo M, Koenig M (Oct 1997). "Frataxin is reduced in Friedreich ataxia patients and is associated with mitochondrial membranes". Human Molecular Genetics. 6 (11): 1771–80. doi:10.1093/hmg/6.11.1771. PMID 9302253.
  • Rötig A, de Lonlay P, Chretien D, Foury F, Koenig M, Sidi D, Munnich A, Rustin P (Oct 1997). "Aconitase and mitochondrial iron-sulphur protein deficiency in Friedreich ataxia". Nature Genetics. 17 (2): 215–7. doi:10.1038/ng1097-215. PMID 9326946.
  • Jiralerspong S, Liu Y, Montermini L, Stifani S, Pandolfo M (1997). "Frataxin shows developmentally regulated tissue-specific expression in the mouse embryo". Neurobiology of Disease. 4 (2): 103–13. doi:10.1006/nbdi.1997.0139. PMID 9331900.
  • Koutnikova H, Campuzano V, Koenig M (Sep 1998). "Maturation of wild-type and mutated frataxin by the mitochondrial processing peptidase". Human Molecular Genetics. 7 (9): 1485–9. doi:10.1093/hmg/7.9.1485. PMID 9700204.
  • Zühlke C, Laccone F, Cossée M, Kohlschütter A, Koenig M, Schwinger E (Jul 1998). "Mutation of the start codon in the FRDA1 gene: linkage analysis of three pedigrees with the ATG to ATT transversion points to a unique common ancestor". Human Genetics. 103 (1): 102–5. doi:10.1007/s004390050791. PMID 9737785.
  • Bartolo C, Mendell JR, Prior TW (Oct 1998). "Identification of a missense mutation in a Friedreich's ataxia patient: implications for diagnosis and carrier studies". American Journal of Medical Genetics. 79 (5): 396–9. doi:10.1002/(SICI)1096-8628(19981012)79:5<396::AID-AJMG13>3.0.CO;2-M. PMID 9779809.
  • Cossée M, Dürr A, Schmitt M, Dahl N, Trouillas P, Allinson P, Kostrzewa M, Nivelon-Chevallier A, Gustavson KH, Kohlschütter A, Müller U, Mandel JL, Brice A, Koenig M, Cavalcanti F, Tammaro A, De Michele G, Filla A, Cocozza S, Labuda M, Montermini L, Poirier J, Pandolfo M (Feb 1999). "Friedreich's ataxia: point mutations and clinical presentation of compound heterozygotes". Annals of Neurology. 45 (2): 200–6. doi:10.1002/1531-8249(199902)45:2<200::AID-ANA10>3.0.CO;2-U. PMID 9989622.
  • Coppola G, De Michele G, Cavalcanti F, Pianese L, Perretti A, Santoro L, Vita G, Toscano A, Amboni M, Grimaldi G, Salvatore E, Caruso G, Filla A (May 1999). "Why do some Friedreich's ataxia patients retain tendon reflexes? A clinical, neurophysiological and molecular study". Journal of Neurology. 246 (5): 353–7. doi:10.1007/s004150050362. PMID 10399865.
  • Branda SS, Cavadini P, Adamec J, Kalousek F, Taroni F, Isaya G (Aug 1999). "Yeast and human frataxin are processed to mature form in two sequential steps by the mitochondrial processing peptidase". The Journal of Biological Chemistry. 274 (32): 22763–9. doi:10.1074/jbc.274.32.22763. PMID 10428860.
  • Gordon DM, Shi Q, Dancis A, Pain D (Nov 1999). "Maturation of frataxin within mammalian and yeast mitochondria: one-step processing by matrix processing peptidase". Human Molecular Genetics. 8 (12): 2255–62. doi:10.1093/hmg/8.12.2255. PMID 10545606.
  • Forrest SM, Knight M, Delatycki MB, Paris D, Williamson R, King J, Yeung L, Nassif N, Nicholson GA (Aug 1998). "The correlation of clinical phenotype in Friedreich ataxia with the site of point mutations in the FRDA gene". Neurogenetics. 1 (4): 253–7. doi:10.1007/s100480050037. PMID 10732799.
  • Al-Mahdawi S, Pook M, Chamberlain S (Jul 2000). "A novel missense mutation (L198R) in the Friedreich's ataxia gene". Human Mutation. 16 (1): 95. doi:10.1002/1098-1004(200007)16:1<95::AID-HUMU29>3.0.CO;2-E. PMID 10874325.
  • Dhe-Paganon S, Shigeta R, Chi YI, Ristow M, Shoelson SE (Oct 2000). "Crystal structure of human frataxin". The Journal of Biological Chemistry. 275 (40): 30753–6. doi:10.1074/jbc.C000407200. PMID 10900192.

External links[edit]