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Published August 2, 2016 | Published + Supplemental Material
Journal Article Open

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.

Additional Information

© 2016 The Author(s). Under a Creative Commons license Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) Received: March 31, 2016; Revised: May 31, 2016; Accepted: June 17, 2016; Published: July 14, 2016. This work was supported by the Rose F. Kennedy Intellectual and Developmental Disabilities Research Center (P30 HD071593) Pilot and Feasibility Award and Grant (to J.G.), NIH grant 7R01NS081366 from the National Institute of Neurological Disorders and Stroke and Polish National Science Center Grant 2015/19/B/NZ1/02804 (to M.N.), and Friedreich's Ataxia Research Alliance and FARA Ireland (to M.N. and J.S.B.). We thank Drs. Sharon Dent (UT MD Anderson Cancer Center), Joel Gottesfeld (The Scripps Research Institute), and Dr. Urszula Polak for helpful comments and support in preparation of this work. Author Contributions: J.G. and M.N. conceived and designed the study. J.G., A.D.B., and J.S.B. performed the experiments and analyzed the results. P.B.D. and J.W.P. generated and provided the polyamide. J.G., J.S.B., and M.N. wrote the manuscript. A.D.B. and Z.R. edited the manuscript.

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Published - 1-s2.0-S2211124716308440-main.pdf

Supplemental Material - mmc1.pdf

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August 20, 2023
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