title: Stalled DNA Replication Forks at the Endogenous GAA Repeats Drive Repeat Expansion in Friedreich's Ataxia Cells.
abstract: Friedreich's ataxia (FRDA) is caused by the expansion of GAA repeats located in the Frataxin (FXN) gene. The GAA repeats continue to expand in FRDA patients, aggravating symptoms and contributing to disease progression. The mechanism leading to repeat expansion and decreased FXN transcription remains unclear. Using single-molecule analysis of replicated DNA, we detected that expanded GAA repeats present a substantial obstacle for the replication machinery at the FXN locus in FRDA cells. Furthermore, aberrant origin activation and lack of a proper stress response to rescue the stalled forks in FRDA cells cause an increase in 3'-5' progressing forks, which could enhance repeat expansion and hinder FXN transcription by head-on collision with RNA polymerases. Treatment of FRDA cells with GAA-specific polyamides rescues DNA replication fork stalling and alleviates expansion of the GAA repeats, implicating DNA triplexes as a replication impediment and suggesting that fork stalling might be a therapeutic target for FRDA.
authors.affiliation: Center for Reproductive Medicine, Weill Cornell Medical College, New York, NY 10065, USA. Electronic address: jeannine.gerhardt@gmail.com.
authors.forename: Jeannine
authors.initials: J
authors.lastname: Gerhardt
authors.affiliation: Department of Biochemistry and Molecular Genetics, UAB Stem Cell Institute, University of Alabama, Birmingham, AL 35294, USA.
authors.forename: Angela D
authors.initials: AD
authors.lastname: Bhalla
authors.affiliation: Department of Biochemistry and Molecular Genetics, UAB Stem Cell Institute, University of Alabama, Birmingham, AL 35294, USA.
authors.forename: Jill Sergesketter
authors.initials: JS
authors.lastname: Butler
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
authors.forename: James W
authors.initials: JW
authors.lastname: Puckett
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
authors.forename: Peter B
authors.initials: PB
authors.lastname: Dervan
authors.affiliation: Center for Reproductive Medicine, Weill Cornell Medical College, New York, NY 10065, USA.
authors.forename: Zev
authors.initials: Z
authors.lastname: Rosenwaks
authors.affiliation: Department of Biochemistry and Molecular Genetics, UAB Stem Cell Institute, University of Alabama, Birmingham, AL 35294, USA; Department of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan 61 704, Poland. Electronic address: mnapiera@uab.edu.
authors.forename: Marek
authors.initials: M
authors.lastname: Napierala
mesh_terms: D002478:Cells, Cultured; D004261:DNA Replication / Q000235:genetics*; D012321:DNA-Directed RNA Polymerases / Q000235:genetics; D018450:Disease Progression; D005621:Friedreich Ataxia / Q000235:genetics*; D006801:Humans; D033862:Iron-Binding Proteins / Q000235:genetics; D019680:Trinucleotide Repeat Expansion / Q000235:genetics*; D000096923:Frataxin
chemical_list: D012321:DNA-Directed RNA Polymerases; D033862:Iron-Binding Proteins; D000096923:Frataxin