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Updated: May 25, 2026
A Reporter Assay to Analyze Intronic microRNA Maturation in Mammalian Cells
Published on: June 16, 2022
Modulation of microRNA processing by mismatch repair protein MutLα
Guogen Mao1, Sanghee Lee, Janice Ortega
1Graduate Center for Toxicology, University of Kentucky College of Medicine, Lexington, KY 40536, USA.
Abstract:
MicroRNAs (miRNAs) are critical post-transcriptional regulators and are derived from hairpin-shaped primary transcripts via a series of processing steps. However, how the production of individual miRNAs is regulated remains largely unknown. Similarly, loss or overexpression of the key mismatch repair protein MutLα (MLH1-PMS2 heterodimer) leads to genome instability and tumorigenesis, but the mechanisms controlling MutLα expression are unknown. Here we demonstrate in vitro and in vivo that MLH1 and miR-422a participate in a feedback loop that regulates the level of both molecules. Using a defined in-vitro miRNA processing system, we show that MutLα stimulates the conversion of pri-miR-422a to pre-miR-422a, as well as the processing of other miRNAs tested, implicating MutLα as a general stimulating factor for miRNA biogenesis. This newly identified MutLα function requires its ATPase and pri-miRNA binding activities. In contrast, miR-422a downregulates MutLα levels by suppressing MLH1 expression through base pairing with the MLH1 3'-untranslated region. A model depicting this feedback mechanism is discussed.
Insights
A novel feedback loop between MutLα (MLH1-PMS2 heterodimer) and microRNA-422a (miR-422a) was discovered. MutLα enhances miRNA production, while miR-422a suppresses MLH1 expression, impacting genome stability.
Area of Science:
- Molecular Biology
- Genetics
- Cancer Research
Background:
- MicroRNAs (miRNAs) are key regulators of gene expression.
- The mismatch repair protein MutLα (MLH1-PMS2) is crucial for genome stability, and its dysregulation is linked to cancer.
- Mechanisms controlling miRNA production and MutLα expression are not fully understood.
Purpose of the Study:
- To investigate the regulatory relationship between MLH1 and miR-422a.
- To elucidate the role of MutLα in miRNA biogenesis.
- To understand how this interaction impacts genome stability and tumorigenesis.
Main Methods:
- In vitro miRNA processing assays using a defined system.
- In vivo studies to validate findings.
- Analysis of MLH1 expression and its interaction with miR-422a using 3'-untranslated region (UTR) base pairing.
Main Results:
- MutLα (MLH1-PMS2) was identified as a novel stimulating factor for miRNA biogenesis, enhancing pri-miRNA to pre-miRNA conversion.
- This MutLα function depends on its ATPase and pri-miRNA binding activities.
- miR-422a was shown to downregulate MutLα levels by suppressing MLH1 expression via binding to the MLH1 3'-UTR.
Conclusions:
- A feedback loop exists where MutLα promotes miRNA production, and miR-422a suppresses MLH1, thereby regulating MutLα levels.
- This regulatory loop has implications for understanding genome instability and cancer development.
- The findings reveal a new layer of post-transcriptional regulation involving DNA repair proteins and miRNAs.
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