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Updated: Jul 28, 2025
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Published on: February 14, 2014
Noncanonical processing by animal 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), DROSHA-DGCR8, processes primary miRNA transcripts (pri-miRNAs) to initiate miRNA biogenesis. The canonical cleavage mechanism of MP has been extensively investigated and comprehensively validated for two decades. However, this canonical mechanism cannot account for the processing of certain pri-miRNAs in animals. In this study, by conducting high-throughput pri-miRNA cleavage assays for approximately 260,000 pri-miRNA sequences, we discovered and comprehensively characterized a noncanonical cleavage mechanism of MP. This noncanonical mechanism does not need several RNA and protein elements essential for the canonical mechanism; instead, it utilizes previously unrecognized DROSHA dsRNA recognition sites (DRESs). Interestingly, the noncanonical mechanism is conserved across animals and plays a particularly significant role in C. elegans. Our established noncanonical mechanism elucidates MP cleavage in numerous RNA substrates unaccounted for by the canonical mechanism in animals. This study suggests a broader substrate repertoire of animal MPs and an expanded regulatory landscape for miRNA biogenesis.
Insights
Researchers discovered a new way Microprocessor (MP) processes microRNA (miRNA) transcripts. This noncanonical mechanism uses novel DROSHA dsRNA recognition sites (DRESs) and expands understanding of miRNA biogenesis.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Microprocessor (MP), comprising DROSHA-DGCR8, is crucial for initiating miRNA biogenesis by processing pri-miRNAs.
- The established canonical cleavage mechanism of MP has been studied for 20 years.
- This canonical pathway, however, fails to explain the processing of all pri-miRNAs in animals.
Purpose of the Study:
- To discover and characterize alternative mechanisms of pri-miRNA processing by MP.
- To investigate the role of novel RNA-protein interactions in miRNA biogenesis.
- To determine the evolutionary conservation and functional significance of alternative MP cleavage pathways.
Main Methods:
- High-throughput pri-miRNA cleavage assays were performed on approximately 260,000 sequences.
- Comparative analysis of canonical versus noncanonical cleavage requirements.
- In silico identification and validation of DROSHA dsRNA recognition sites (DRESs).
Main Results:
- A novel, noncanonical MP cleavage mechanism was identified and characterized.
- This noncanonical pathway does not require key elements of the canonical mechanism.
- It relies on previously unrecognized DROSHA dsRNA recognition sites (DRESs).
- The noncanonical mechanism is conserved across animal species, notably important in C. elegans.
Conclusions:
- The noncanonical MP cleavage mechanism accounts for processing of pri-miRNA substrates missed by the canonical pathway.
- This finding broadens the known substrate range for animal MPs.
- It suggests an expanded regulatory network for miRNA biogenesis.
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