Related Experiment Video
Updated: May 4, 2026
A Microfluidic Platform for Longitudinal Imaging in Caenorhabditis elegans
Published on: May 2, 2018
Regulation of Microprocessor assembly and localization via Pasha's WW domain in C. elegans
Brooke E Montgomery1, Thiago L Knittel1, Kailee J Reed1,2
1Department of Biology, Colorado State University, Fort Collins, CO 80523, USA.
Abstract:
Primary microRNA (pri-miRNA) transcripts are processed by the Microprocessor, a protein complex that includes the ribonuclease Drosha and its RNA binding partner DGCR8/Pasha. We developed a live, whole animal, fluorescence-based sensor that reliably monitors pri-miRNA processing with high sensitivity in C. elegans. Through a forward genetic selection for alleles that desilence the sensor, we identified a mutation in the conserved G residue adjacent to the namesake W residue of Pasha's WW domain. Using genome editing we also mutated the W residue and reveal that both the G and W residue are required for dimerization of Pasha and proper assembly of the Microprocessor. Surprisingly, we find that the WW domain also facilitates nuclear localization of Pasha, which in turn promotes nuclear import or retention of Drosha. Furthermore, depletion of Pasha or Drosha causes both components of the Microprocessor to mislocalize to the cytoplasm. Thus, Pasha and Drosha mutually regulate each other's spatial expression in C. elegans.
Insights
Researchers developed a live sensor to track microRNA processing in C. elegans. They discovered that specific residues in Pasha are crucial for Microprocessor assembly and nuclear localization of Pasha and Drosha.
Area of Science:
- Molecular Biology
- Genetics
- Developmental Biology
Background:
- MicroRNA (miRNA) biogenesis is a critical regulatory process involving the Microprocessor complex, composed of Drosha and DGCR8 (also known as Pasha).
- Accurate pri-miRNA processing by the Microprocessor is essential for gene expression regulation.
- Understanding the assembly and localization dynamics of the Microprocessor is key to deciphering miRNA biogenesis control.
Approach:
- Developed a novel, live, whole-animal, fluorescence-based sensor for sensitive monitoring of pri-miRNA processing in Caenorhabditis elegans.
- Utilized forward genetic screening to identify mutations affecting pri-miRNA processing.
- Employed genome editing techniques to precisely mutate key residues within the Pasha protein.
Key Points:
- Identified specific mutations in the WW domain of Pasha, including conserved G and W residues, essential for Microprocessor complex assembly.
- Demonstrated that the Pasha WW domain is critical for its own nuclear localization.
- Revealed that Pasha facilitates the nuclear import or retention of Drosha, highlighting a mutual regulatory mechanism.
Conclusions:
- Pasha and Drosha mutually regulate each other's localization within the cell, with Pasha playing a key role in Microprocessor assembly and nuclear import.
- The WW domain of Pasha is a critical structural and functional motif for Microprocessor function and localization.
- This study provides new insights into the intricate regulation of miRNA biogenesis in vivo.
