Stalled DNA Replication Forks at the Endogenous GAA Repeats Drive Repeat Expansion in Friedreich's Ataxia Cells.

TitleStalled DNA Replication Forks at the Endogenous GAA Repeats Drive Repeat Expansion in Friedreich's Ataxia Cells.
Publication TypeJournal Article
Year of Publication2016
AuthorsGerhardt J, Bhalla AD, Butler JSergeskett, Puckett JW, Dervan PB, Rosenwaks Z, Napierala M
JournalCell Rep
Volume16
Issue5
Pagination1218-1227
Date Published2016 08 02
ISSN2211-1247
KeywordsCells, Cultured, Disease Progression, DNA Replication, DNA-Directed RNA Polymerases, Friedreich Ataxia, Humans, Iron-Binding Proteins, Trinucleotide Repeat Expansion
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.

DOI10.1016/j.celrep.2016.06.075
Alternate JournalCell Rep
PubMed ID27425605
PubMed Central IDPMC5028224
Grant ListP30 HD071593 / HD / NICHD NIH HHS / United States
R01 NS081366 / NS / NINDS NIH HHS / United States