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Dissection of the Caenorhabditis elegans Microprocessor
Thuy Linh Nguyen1, Trung Duc Nguyen1, Minh Khoa Ngo1
1Division of Life Science, The Hong Kong University of Science & Technology, Hong Kong, China.
Abstract:
Microprocessor (MP) is a complex involved in initiating the biogenesis of microRNAs (miRNAs) by cleaving primary microRNAs (pri-miRNAs). miRNAs are small single-stranded RNAs that play a key role in the post-transcriptional regulation of gene expression. Thus, understanding the molecular mechanism of MP is critical for interpreting the roles of miRNAs in normal cellular processes and during the onset of various diseases. MP comprises a ribonuclease enzyme, DROSHA, and a dimeric RNA-binding protein, which is called DGCR8 in humans and Pasha in Caenorhabditis elegans. DROSHA cleaves stem-loop structures located within pri-miRNAs to generate pre-miRNAs. Although the molecular mechanism of human MP (hMP; hDROSHA-DGCR8) is well understood, that of Caenorhabditis elegans MP (cMP; cDrosha-Pasha) is still largely unknown. Here, we reveal the molecular mechanism of cMP and show that it is distinct from that of hMP. We demonstrate that cDrosha and Pasha measure ∼16 and ∼25 bp along a pri-miRNA stem, respectively, and they work together to determine the site of cMP cleavage in pri-miRNAs. We also demonstrate the molecular basis for their substrate measurement. Thus, our findings reveal a previously unknown molecular mechanism of cMP; demonstrate the differences between the mechanisms of hMP and cMP; and provide a foundation for revealing the mechanisms regulating miRNA expression in different animal species.
Insights
The microRNA processing complex (MP) mechanism in Caenorhabditis elegans differs from humans. Researchers uncovered how cDrosha and Pasha proteins measure pri-miRNA stems to determine cleavage sites, revealing distinct miRNA biogenesis pathways.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- MicroRNAs (miRNAs) are crucial regulators of gene expression at the post-transcriptional level.
- The Microprocessor complex (MP), comprising DROSHA and DGCR8/Pasha, initiates miRNA biogenesis by processing pri-miRNAs.
- Understanding MP mechanisms is vital for comprehending miRNA roles in cellular processes and diseases.
Purpose of the Study:
- To elucidate the molecular mechanism of the Caenorhabditis elegans Microprocessor complex (cMP).
- To compare the cMP mechanism with the well-characterized human MP (hMP).
- To identify the distinct features of cMP in pri-miRNA processing.
Main Methods:
- Biochemical assays to analyze the interaction of cDrosha and Pasha with pri-miRNAs.
- Determination of the specific binding sites and lengths measured by cDrosha and Pasha on pri-miRNA stems.
- Comparative analysis of cMP and hMP substrate recognition and cleavage.
Main Results:
- The cMP complex exhibits a distinct mechanism compared to hMP.
- cDrosha measures approximately 16 base pairs and Pasha measures approximately 25 base pairs along the pri-miRNA stem.
- These measurements dictate the precise cleavage site selection by cMP.
Conclusions:
- A novel molecular mechanism for cMP-mediated pri-miRNA processing has been revealed.
- Significant mechanistic differences exist between cMP and hMP.
- This study provides a foundation for understanding species-specific regulation of miRNA biogenesis.
