Activating frataxin expression by repeat-targeted nucleic acids.

Liande Li,David R Corey,Masayuki Matsui

doi:10.1038/ncomms10606

Liande Li, David R Corey + Show 1 more

Open Access

https://doi.org/10.1038/ncomms10606

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Abstract

Friedreich's ataxia is an incurable genetic disorder caused by a mutant expansion of the trinucleotide GAA within an intronic FXN RNA. This expansion leads to reduced expression of frataxin (FXN) protein and evidence suggests that transcriptional repression is caused by an R-loop that forms between the expanded repeat RNA and complementary genomic DNA. Synthetic agents that increase levels of FXN protein might alleviate the disease. We demonstrate that introducing anti-GAA duplex RNAs or single-stranded locked nucleic acids into patient-derived cells increases FXN protein expression to levels similar to analogous wild-type cells. Our data are significant because synthetic nucleic acids that target GAA repeats can be lead compounds for restoring curative FXN levels. More broadly, our results demonstrate that interfering with R-loop formation can trigger gene activation and reveal a new strategy for upregulating gene expression.

Highlights

Friedreich’s ataxia is an incurable genetic disorder caused by a mutant expansion of the trinucleotide GAA within an intronic FXN RNA
Friedreich’s ataxia (FRDA) is an incurable genetic disorder caused by reduced expression of the mitochondrial protein frataxin (FXN)[1,2]
To determine whether enhanced protein stability might be involved in gene activation we examined FXN messenger RNAs (mRNAs) stability upon treatment with anti-GAA duplex RNA

Summary

Introduction

Friedreich’s ataxia is an incurable genetic disorder caused by a mutant expansion of the trinucleotide GAA within an intronic FXN RNA This expansion leads to reduced expression of frataxin (FXN) protein and evidence suggests that transcriptional repression is caused by an R-loop that forms between the expanded repeat RNA and complementary genomic DNA. Evidence suggests that the expanded GAA tract within the nascent FXN transcript binds to genomic DNA to form an R-loop[15,16,17,18,19] This R-loop may interfere with transcription and reduce FXN expression (Fig. 1b), possibly by inducing silencing chromatin modifications that impeded transcriptional elongation[20,21]. We set out to test this hypothesis using repeat-targeted duplex RNAs and single-stranded locked nucleic acid (LNA) oligonucleotides

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Results

Conclusion