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RNAi Interference by dsRNA Injection into Drosophila Embryos
Published on: April 11, 2011
The insertion in the double-stranded RNA binding domain of human Drosha is important for its function
Xiaoxiao Zhang1, Peng Li1, Jian Lin1
1Department of Zoology, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China.
Abstract:
microRNAs (miRNAs) are first transcribed as long, primary transcripts, which are then processed by multiple enzymes and proteins to generate the single-stranded, approximately 22-nucleotide (nt)-long mature miRNAs. A critical step in animal miRNA biogenesis is the cleavage of primary miRNA transcripts (pri-miRNAs) to produce precursor miRNAs (pre-miRNAs) by the enzyme Drosha. How Drosha recognizes its substrates remains incompletely understood. In this study we constructed a series of human Drosha mutants and examined their enzymatic activities and interaction with RNAs. We found that the N-terminal region is required for the nuclear localization and cellular function of Drosha. And in contrast to previous reports, we showed that the double-stranded RNA binding domain (RBD) of Drosha exhibited a weak but noticeable affinity for RNA. Compared to the RBDs of other RNA-binding proteins, the RBD of Drosha has a short insert, whose mutations reduced RNA binding and pri-miRNA cleavage. Overexpression of Drosha RBD mutants in a reporter assay corroborated their deficiencies in Drosha activity in cell cultures. In addition, we found that point mutations in the RNaseIIIb domain of Drosha implicated in Wilms tumors differentially affected cleavage of the 5' and 3' strands of pri-miRNAs in vitro. In conclusion, our results provided important insights into the mechanism of pri-miRNA processing by human Drosha.
Insights
Human Drosha enzyme processing of microRNAs (miRNAs) involves its N-terminal region for nuclear function and its RNA-binding domain (RBD) for substrate recognition. Mutations in Drosha
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- MicroRNAs (miRNAs) are key regulators of gene expression, processed from primary transcripts.
- The enzyme Drosha initiates miRNA biogenesis by cleaving primary miRNA transcripts (pri-miRNAs).
- The precise mechanism of Drosha substrate recognition remains incompletely understood.
Purpose of the Study:
- To investigate the functional domains of human Drosha involved in pri-miRNA processing.
- To elucidate the role of the Drosha RNA-binding domain (RBD) in substrate interaction.
- To analyze the impact of specific Drosha mutations on its enzymatic activity and cellular function.
Main Methods:
- Construction and characterization of human Drosha mutants.
- Enzymatic activity assays and RNA binding studies.
- Reporter assays for cellular function and in vitro cleavage assays.
Main Results:
- The N-terminal region of Drosha is essential for nuclear localization and cellular function.
- Drosha's double-stranded RNA binding domain (RBD) shows RNA affinity, with a short insert critical for binding and cleavage.
- Mutations in the RNaseIIIb domain differentially affect 5' and 3' pri-miRNA strand cleavage.
Conclusions:
- The study provides critical insights into the molecular mechanisms of human Drosha in pri-miRNA processing.
- Drosha's N-terminal region and RBD play distinct but crucial roles in miRNA biogenesis.
- Understanding Drosha function is vital for comprehending gene regulation and associated diseases.
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