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Updated: Aug 16, 2026
Exploring Sequence Space to Identify Binding Sites for Regulatory RNA-Binding Proteins
Published on: August 9, 2019
HnRNP H inhibits nuclear export of mRNA containing expanded CUG repeats and a distal branch point sequence
Dong-Ho Kim1, Marc-Andre Langlois, Kwang-Back Lee
1Department of Molecular Biology, Beckman Research Institute of the City of Hope Duarte, CA, USA.
Abstract:
Myotonic dystrophy type 1 (DM1) is an autosomal dominant neuromuscular disorder associated with a (CUG)n expansion in the 3'-untranslated region of the DMPK (DM1 protein kinase) gene. Mutant DMPK mRNAs containing the trinucleotide expansion are retained in the nucleus of DM1 cells and form discrete foci. The nuclear sequestration of RNA binding proteins and associated factors binding to the CUG expansions is believed to be responsible for several of the splicing defects observed in DM1 patients and could ultimately be linked to DM1 muscular pathogenesis. Several RNA binding proteins capable of co-localizing with the nuclear-retained mutant DMPK mRNAs have already been identified but none can account for the nuclear retention of the mutant transcripts. Here, we have employed a modified UV crosslinking assay to isolate proteins bound to mutant DMPK-derived RNA and have identified hnRNP H as an abundant candidate. The specific binding of hnRNP H requires not only a CUG repeat expansion but also a splicing branch point distal to the repeats. Suppression of hnRNP H expression by RNAi rescued nuclear retention of RNA with CUG repeat expansions. The identification of hnRNP H as a factor capable of binding and possibly modulating nuclear retention of mutant DMPK mRNA may prove to be an important link in our understanding of the molecular mechanisms that lead to DM1 pathogenesis.
Insights
Researchers identified heterogeneous nuclear ribonucleoprotein H (hnRNP H) as a key protein involved in Myotonic dystrophy type 1 (DM1). This discovery sheds light on the molecular mechanisms driving DM1 pathogenesis and nuclear RNA retention.
Area of Science:
- Molecular Biology
- Genetics
- Neuroscience
Background:
- Myotonic dystrophy type 1 (DM1) is an inherited neuromuscular disorder.
- It is caused by a (CUG)n repeat expansion in the DMPK gene.
- Mutant DMPK mRNAs accumulate in the nucleus, sequestering RNA-binding proteins and causing splicing defects.
Purpose of the Study:
- To identify proteins that bind to the expanded CUG repeats in mutant DMPK mRNA.
- To understand the role of these proteins in the nuclear retention of mutant transcripts in DM1.
- To elucidate the molecular mechanisms underlying DM1 pathogenesis.
Main Methods:
- Modified UV crosslinking assay to isolate proteins bound to mutant DMPK RNA.
- Identification of bound proteins using biochemical techniques.
- RNA interference (RNAi) to suppress hnRNP H expression.
- Assessment of RNA nuclear retention after hnRNP H suppression.
Main Results:
- hnRNP H was identified as an abundant protein bound to mutant DMPK-derived RNA.
- hnRNP H binding is dependent on both the CUG repeat expansion and a distal splicing branch point.
- Suppression of hnRNP H expression using RNAi rescued the nuclear retention of expanded CUG repeat RNA.
- hnRNP H plays a significant role in the nuclear retention of mutant DMPK mRNA.
Conclusions:
- hnRNP H is a crucial factor in the nuclear retention of mutant DMPK mRNA in DM1.
- This finding provides a potential link between RNA binding proteins and DM1 pathogenesis.
- Targeting hnRNP H may offer therapeutic strategies for DM1.
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