Replication Stress Induces Global Chromosome Breakage in the Fragile X Genome

Arijita Chakraborty, Piroon Jenjaroenpun, Jing Li, Sami El Hilali, Andrew McCulley, Brian Haarer, Elizabeth A. Hoffman, Aimee Belak, Audrey Thorland, Heidi Hehnly, Carl Schildkraut, Chun long Chen, Vladimir A. Kuznetsov, Wenyi Feng

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


Fragile X syndrome (FXS) is a neurodevelopmental disorder caused by mutations in the FMR1 gene and deficiency of a functional FMRP protein. FMRP is known as a translation repressor whose nuclear function is not understood. We investigated the global impact on genome stability due to FMRP loss. Using Break-seq, we map spontaneous and replication stress-induced DNA double-strand breaks (DSBs) in an FXS patient-derived cell line. We report that the genomes of FXS cells are inherently unstable and accumulate twice as many DSBs as those from an unaffected control. We demonstrate that replication stress-induced DSBs in FXS cells colocalize with R-loop forming sequences. Exogenously expressed FMRP in FXS fibroblasts ameliorates DSB formation. FMRP, not the I304N mutant, abates R-loop-induced DSBs during programmed replication-transcription conflict. These results suggest that FMRP is a genome maintenance protein that prevents R-loop accumulation. Our study provides insights into the etiological basis for FXS. Chakraborty et al. report a genome-wide increase of DNA double-strand breaks in fragile X syndrome patient cells and suggest that FMRP functions in the R-loop pathway to prevent genome instability induced by DNA replication-transcription conflicts.

Original languageEnglish (US)
Article number108179
JournalCell Reports
Issue number12
StatePublished - Sep 22 2020


  • DNA double-strand breaks
  • DNA replication stress
  • DSB
  • FMRP
  • FXS
  • I304N
  • R-loops
  • chromosome fragile sites
  • fragile X syndrome
  • genome instability

ASJC Scopus subject areas

  • General Biochemistry, Genetics and Molecular Biology


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