Relief of microRNA-mediated translational repression in human cells subjected to stress
Suvendra N Bhattacharyya1, Regula Habermacher, Ursula Martine
1Friedrich Miescher Institute for Biomedical Research, P.O. Box 2543, 4002 Basel, Switzerland.
Abstract:
In metazoans, most microRNAs imperfectly base-pair with the 3' untranslated region (3'UTR) of target mRNAs and prevent protein accumulation by either repressing translation or inducing mRNA degradation. Examples of specific mRNAs undergoing microRNA-mediated repression are numerous, but whether the repression is a reversible process remains largely unknown. Here we show that cationic amino acid transporter 1 (CAT-1) mRNA and reporters bearing its 3'UTR can be relieved from the microRNA miR-122-induced inhibition in human hepatocarcinoma cells subjected to different stress conditions. The derepression of CAT-1 mRNA is accompanied by its release from cytoplasmic processing bodies and its recruitment to polysomes. The derepression requires binding of HuR, an AU-rich-element binding protein, to the 3'UTR of CAT-1 mRNA. We propose that proteins interacting with the 3'UTR will generally act as modifiers altering the potential of miRNAs to repress gene expression.
Insights
MicroRNA repression of gene expression is reversible. Stress conditions can release cationic amino acid transporter 1 (CAT-1) mRNA from miR-122 inhibition, restoring protein production.
Area of Science:
- Molecular Biology
- Gene Regulation
- RNA Biology
Background:
- MicroRNAs (miRNAs) are key regulators of gene expression in metazoans.
- miRNAs typically bind to the 3' untranslated region (3'UTR) of target mRNAs, inhibiting protein synthesis or promoting mRNA decay.
- The reversibility of miRNA-mediated repression remains largely unexplored.
Purpose of the Study:
- To investigate whether miRNA-induced gene silencing is a reversible process.
- To identify mechanisms underlying the potential derepression of target mRNAs.
- To examine the role of stress conditions in modulating miRNA activity.
Main Methods:
- Utilized human hepatocarcinoma cells.
- Studied the regulation of cationic amino acid transporter 1 (CAT-1) mRNA by miR-122.
- Employed reporter assays to assess gene expression.
- Investigated the subcellular localization of mRNA and protein interactions using techniques like polysome profiling and RNA-binding protein analysis.
Main Results:
- Demonstrated that miR-122-induced inhibition of CAT-1 mRNA and its 3'UTR reporters is reversible under stress conditions.
- Observed that derepressed CAT-1 mRNA is released from processing bodies and recruited to polysomes.
- Showed that the binding of HuR (AU-rich-element binding protein) to the CAT-1 3'UTR is essential for this derepression process.
Conclusions:
- miRNA-mediated gene repression is not always a permanent state and can be reversed.
- Stress-induced derepression of specific mRNAs involves the release from inhibitory complexes and subsequent translation.
- Proteins like HuR that interact with the 3'UTR can modulate miRNA efficacy, suggesting a broader role in gene expression control.
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