title: Expression of human frataxin is regulated by transcription factors SRF and TFAP2.
abstract: BACKGROUND
  Friedreich ataxia is an autosomal recessive neurodegenerative disease caused by reduced expression levels of the frataxin gene (FXN) due to expansion of triplet nucleotide GAA repeats in the first intron of FXN. Augmentation of frataxin expression levels in affected Friedreich ataxia patient tissues might substantially slow disease progression.
  
  
  RESULTS
  We utilized bioinformatic tools in conjunction with chromatin immunoprecipitation and electrophoretic mobility shift assays to identify transcription factors that influence transcription of the FXN gene. We found that the transcription factors SRF and TFAP2 bind directly to FXN promoter sequences. SRF and TFAP2 binding sequences in the FXN promoter enhanced transcription from luciferase constructs, while mutagenesis of the predicted SRF or TFAP2 binding sites significantly decreased FXN promoter activity. Further analysis demonstrated that robust SRF- and TFAP2-mediated transcriptional activity was dependent on a regulatory element, located immediately downstream of the first FXN exon. Finally, over-expression of either SRF or TFAP2 significantly increased frataxin mRNA and protein levels in HEK293 cells, and frataxin mRNA levels were also elevated in SH-SY5Y cells and in Friedreich ataxia patient lymphoblasts transfected with SRF or TFAP2.
  
  
  CONCLUSIONS
  We identified two transcription factors, SRF and TFAP2, as well as an intronic element encompassing EGR3-like sequence, that work together to regulate expression of the FXN gene. By providing new mechanistic insights into the molecular factors influencing frataxin expression, our results should aid in the discovery of new therapeutic targets for the treatment of Friedreich ataxia.
authors.affiliation: Jiangsu Key Laboratory for Molecular Medicine, Medical School of Nanjing University, Nanjing, China. likuanyu@nju.edu.cn
authors.forename: Kuanyu
authors.initials: K
authors.lastname: Li
authors.forename: Anamika
authors.initials: A
authors.lastname: Singh
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Crooks
authors.forename: Xiaoman
authors.initials: X
authors.lastname: Dai
authors.forename: Zhuangzhuang
authors.initials: Z
authors.lastname: Cong
authors.forename: Liang
authors.initials: L
authors.lastname: Pan
authors.forename: Dung
authors.initials: D
authors.lastname: Ha
authors.forename: Tracey A
authors.initials: TA
authors.lastname: Rouault
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D019295:Computational Biology; D005621:Friedreich Ataxia / Q000473:pathology / Q000628:therapy; D005786:Gene Expression Regulation; D006801:Humans; D007501:Iron / Q000378:metabolism; D033862:Iron-Binding Proteins / Q000235:genetics*; D051379:Mice; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D026362:Serum Response Factor / Q000378:metabolism*; D050656:Transcription Factor AP-2 / Q000378:metabolism*; D015854:Up-Regulation; D000096923:Frataxin
chemical_list: D007501:Iron; D033862:Iron-Binding Proteins; D012333:RNA, Messenger; D026362:Serum Response Factor; D050656:Transcription Factor AP-2; D000096923:Frataxin; C476858:SRF protein, human
references.citation: Biochemistry. 2002 May 28;41(21):6798-804
references.pmid: 12022884
references.citation: Hum Mol Genet. 2003 Apr 15;12(8):879-89
references.pmid: 12668611
references.citation: Biochim Biophys Acta. 2001 May 31;1536(2-3):133-40
references.pmid: 11406348
references.citation: J Neuroinflammation. 2009 May 18;6:16
references.pmid: 19450264
references.citation: Genome Biol. 2005;6(13):246
references.pmid: 16420676
references.citation: PLoS One. 2008 Apr 09;3(4):e1958
references.pmid: 18463734
references.citation: FEBS Lett. 2004 Jan 16;557(1-3):215-20
references.pmid: 14741370
references.citation: Nucleic Acids Res. 2000 Apr 15;28(8):1808-18
references.pmid: 10734201
references.citation: Nucleic Acids Res. 2007;35(10):3383-90
references.pmid: 17478498
references.citation: J Immunol. 2007 Jun 1;178(11):6796-805
references.pmid: 17513727
references.citation: Hum Mol Genet. 1997 Oct;6(11):1771-80
references.pmid: 9302253
references.citation: Proc Natl Acad Sci U S A. 2005 Nov 8;102(45):16345-50
references.pmid: 16258061
references.citation: Biochem J. 1998 Dec 1;336 ( Pt 2):327-35
references.pmid: 9820808
references.citation: Nucleic Acids Res. 2000 Jul 15;28(14):2815-22
references.pmid: 10908340
references.citation: Hum Mol Genet. 2008 Aug 1;17(15):2265-73
references.pmid: 18424449
references.citation: Hum Mol Genet. 2008 Mar 1;17(5):735-46
references.pmid: 18045775
references.citation: Expert Opin Investig Drugs. 2003 Apr;12(4):569-75
references.pmid: 12665413
references.citation: Nat Rev Neurol. 2009 Apr;5(4):222-34
references.pmid: 19347027
references.citation: Nucleic Acids Res. 2001 Jun 1;29(11):2338-48
references.pmid: 11376152
references.citation: Ann Neurol. 1997 May;41(5):675-82
references.pmid: 9153531
references.citation: DNA Cell Biol. 2009 Sep;28(9):425-34
references.pmid: 19558215
references.citation: Nat Genet. 1998 Sep;20(1):87-91
references.pmid: 9731539
references.citation: Proc Natl Acad Sci U S A. 1990 Jun;87(11):4299-303
references.pmid: 2349238
references.citation: Nucleic Acids Res. 2000 Dec 15;28(24):4930-7
references.pmid: 11121484
references.citation: Arch Neurol. 2005 Apr;62(4):621-6
references.pmid: 15824263
references.citation: Science. 1996 Mar 8;271(5254):1423-7
references.pmid: 8596916
references.citation: J Biol Chem. 1996 Apr 26;271(17):9947-54
references.pmid: 8626632
references.citation: Am J Hum Genet. 2008 Jul;83(1):77-88
references.pmid: 18597733
references.citation: Can J Neurol Sci. 1976 Nov;3(4):349-54
references.pmid: 187309
references.citation: J Am Chem Soc. 2003 May 21;125(20):6078-84
references.pmid: 12785837
references.citation: Blood. 2008 Dec 15;112(13):5219-27
references.pmid: 18796625
references.citation: Trends Neurosci. 2009 Aug;32(8):432-42
references.pmid: 19643506
references.citation: Nat Genet. 1997 Oct;17(2):215-7
references.pmid: 9326946
references.citation: Genomics. 2005 Feb;85(2):221-30
references.pmid: 15676280
references.citation: Nucleic Acids Res. 2008 Nov;36(19):6056-65
references.pmid: 18820300
references.citation: Science. 1997 Jun 13;276(5319):1709-12
references.pmid: 9180083
references.citation: Nucleic Acids Res. 2007;35(4):1075-84
references.pmid: 17264130