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A Double Jeopardy: Loss of FMRP Results in DSB and Down-regulated DNA Repair
Arijita Chakraborty1,2, Andre Grageda1,3, Vladimir A Kuznetsov1,3
1Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA.
Abstract:
Our understanding of the molecular functions of the nucleocytoplasmic FMRP protein, which, if absent or dysfunctional, causes the fragile X syndrome (FXS), largely revolves around its involvement in protein translation regulation in the cytoplasm. Recent studies have begun honing in on the nuclear and genomic functions of FMRP. We have shown that during DNA replication stress, cells derived from FXS patients sustain increased level of R-loop formation and DNA double strand breaks. Here, we describe a transcriptomic analysis of these cells in order to identify those genes most impacted by the loss of FMRP with and without replication stress. We show that FMRP loss causes transcriptomic changes previously reported in untreated conditions. Importantly, we also show that replication stress, in addition to causing excess of DSB, results in down-regulation of transcription in virtually all DNA repair pathways. This finding suggests that despite normal DNA damage response, FXS patient-derived cells experience R-loop-induced DNA breakage as well as impaired DNA repair functions, effectively a double jeopardy. We suggest that it is imperative to deepen the understanding of the nuclear functions, particularly a genome protective function, of FMRP, which will lead to discoveries of novel therapeutic interventions for the FXS.
Insights
Fragile X syndrome (FXS) patient cells show increased DNA damage and impaired DNA repair. Loss of FMRP protein exacerbates these issues, especially under replication stress, highlighting its crucial genome protective role.
Area of Science:
- Genetics
- Molecular Biology
- Neuroscience
Background:
- Fragile X syndrome (FXS) is linked to FMRP protein dysfunction, primarily studied for cytoplasmic roles in translation.
- Emerging research highlights FMRP's nuclear and genomic functions.
- FXS patient cells exhibit elevated R-loop formation and DNA double-strand breaks (DSBs) during replication stress.
Purpose of the Study:
- To investigate the transcriptomic changes in FXS patient cells lacking FMRP, with and without replication stress.
- To identify genes significantly affected by FMRP loss under normal and stressed conditions.
Main Methods:
- Transcriptomic analysis of FXS patient-derived cells.
- Comparison of gene expression profiles with and without induced replication stress.
Main Results:
- FMRP loss induces transcriptomic alterations consistent with previous findings in untreated FXS cells.
- Replication stress in FXS cells leads to increased DSBs and widespread transcriptional downregulation across DNA repair pathways.
- FXS cells exhibit R-loop-induced DNA breakage and compromised DNA repair, a "double jeopardy" scenario.
Conclusions:
- FMRP plays a critical role in genome protection within the nucleus.
- Understanding FMRP's nuclear functions is essential for developing novel therapeutic strategies for FXS.
- Targeting FMRP's genome protective mechanisms may offer new avenues for FXS treatment.
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