Abstract

Friedreich's ataxia (FRDA) is an autosomal recessive disease caused by an intronic GAA.TTC triplet repeat expansion. FRDA is the most common hereditary ataxia. The FRDA gene is spread over 40 kb and contains five exons which encode a 210 amino acid protein named frataxin. Normal individuals contain 7-22 GAA.TTC units whereas FRDA patients have enlarge and polymorphic alleles with 100-1700 units. The expansion of the GAA.TTC repeat in the first intron of the frataxin gene results in reduced levels of frataxin mRNA and protein. Shorter lengths of GAA.TTC repeats adopt intra- and inter-molecular triplexes and long repeats (>60 units) form one of several possible unusual conformations. Our recent discovery that 150 and 270 repeats of GAA.TTC adopt a dramatically new form of """"""""bent"""""""" DNA heightens the interest in the role of DNA conformation in the molecular etiology of this disease. The goal is to elucidate the nucleic acid molecular mechanisms responsible for FRDA.
Aim 1 is to study the conformations of different lengths of GAA.TTC from normal individuals to the enlarged alleles. Characterization will be by hydrodynamic properties, chemical and enzymatic probe analysis, EM, circularization kinetics and helical repeat studies. Also, the conformations formed between DNA GAA.TTC and intronic rGAA will be investigated.
Aim 2 is to study the transcription properties of the FRDA TRS structures by nuclear runoff experiments from patient materials, determinations of the transcription elongation rate in vitro, and studies on the RNA as well as mRNA.DNA structures. Also, the fidelity of transcription will be monitored along with the effects of transcription on repeat stability. Our new data revealed the inhibitory effects of expanded intronic genetic instabilities of the FRDA triplet repeat sequences (TRS) in vivo and vitro. In summary, we shall study the molecular etiology of FRDA by elucidating the DNA conformations of different lengths of GAA.TTC and their effect on transcription and on genetic instabilities (replication and recombination).

  Funding Agency

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
7R01NS037554-02
Application #
6212347
Study Section
Biochemistry Study Section (BIO)
Program Officer
Spinella, Giovanna M
Project Start
1999-01-01
Project End
2002-12-31
Budget Start
2000-01-01
Budget End
2000-12-31
Support Year
2
Fiscal Year
2000
Total Cost
$256,138
Indirect Cost

  Institution

Name
Texas A&M University
Department
Genetics
Type
Schools of Medicine
DUNS #
City
College Station
State
TX
Country
United States
Zip Code
77845

  Publications

Chuzhanova, Nadia; Chen, Jian-Min; Bacolla, Albino et al. (2009) Gene conversion causing human inherited disease: evidence for involvement of non-B-DNA-forming sequences and recombination-promoting motifs in DNA breakage and repair. Hum Mutat 30:1189-98
Kosmider, Beata; Wells, Robert D (2007) Fragile X repeats are potent inducers of complex, multiple site rearrangements in flanking sequences in Escherichia coli. DNA Repair (Amst) 6:1850-63
Dere, Ruhee; Wells, Robert D (2006) DM2 CCTG*CAGG repeats are crossover hotspots that are more prone to expansions than the DM1 CTG*CAG repeats in Escherichia coli. J Mol Biol 360:21-36
Bacolla, Albino; Wojciechowska, Marzena; Kosmider, Beata et al. (2006) The involvement of non-B DNA structures in gross chromosomal rearrangements. DNA Repair (Amst) 5:1161-70
Wojciechowska, Marzena; Napierala, Marek; Larson, Jacquelynn E et al. (2006) Non-B DNA conformations formed by long repeating tracts of myotonic dystrophy type 1, myotonic dystrophy type 2, and Friedreich's ataxia genes, not the sequences per se, promote mutagenesis in flanking regions. J Biol Chem 281:24531-43
Bacolla, Albino; Collins, Jack R; Gold, Bert et al. (2006) Long homopurine*homopyrimidine sequences are characteristic of genes expressed in brain and the pseudoautosomal region. Nucleic Acids Res 34:2663-75
Burnett, Ryan; Melander, Christian; Puckett, James W et al. (2006) DNA sequence-specific polyamides alleviate transcription inhibition associated with long GAA.TTC repeats in Friedreich's ataxia. Proc Natl Acad Sci U S A 103:11497-502
Wojciechowska, Marzena; Bacolla, Albino; Larson, Jacquelynn E et al. (2005) The myotonic dystrophy type 1 triplet repeat sequence induces gross deletions and inversions. J Biol Chem 280:941-52
Hebert, Micheal L; Spitz, Leslie A; Wells, Robert D (2004) DNA double-strand breaks induce deletion of CTG.CAG repeats in an orientation-dependent manner in Escherichia coli. J Mol Biol 336:655-72
Bacolla, Albino; Jaworski, Adam; Larson, Jacquelynn E et al. (2004) Breakpoints of gross deletions coincide with non-B DNA conformations. Proc Natl Acad Sci U S A 101:14162-7

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