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Published on: June 2, 2018
Clarifying mammalian RISC assembly in vitro.
Grace S Tan1, Barry G Garchow, Xuhang Liu
1Department of Medicine, Division of Rheumatology, University of Pennsylvania School of Medicine, Philadelphia, PA, USA.
Argonaute 2 (Ago2) binds microRNA precursors (pre-miRNAs), forming active complexes. This study defines the minimal factors, Ago2 and Dicer, sufficient for pre-miRNA processing and RNA-induced silencing complex (RISC) loading.
Area of Science:
- Molecular Biology
- Gene Regulation
- RNA Biology
Background:
- Argonaute (Ago) proteins are central to RNA-induced silencing complex (RISC) function.
- Ago2 can bind mature microRNAs (miRNAs) and miRNA precursors (pre-miRNAs).
- Ago2:pre-miRNA complexes are catalytically active and form non-canonical RISCs.
Purpose of the Study:
- Characterize Ago2:pre-miRNA complexes.
- Identify target RNAs for pre-miRNAs.
- Define factors required for in vitro pre-miRNA processing and RISC loading.
Main Methods:
- Identification of target RNAs unique to miRNAs over pre-miRNAs.
- In vitro recapitulation of pre-miRNA processing.
- In vitro reconstitution of canonical RISC loading.
Main Results:
- Ago2 binding to pre-miRNAs bypasses Dicer activity.
- Identified specific target RNAs to study pre-miRNA processing.
- Defined Ago2 and Dicer as sufficient for miRNA processing and RISC loading.
Conclusions:
- Ago2 and Dicer are sufficient for miRNA processing and loading into RISC.
- Ago2 binds to the 5'-end or alternatively the 3'-end of select pre-miRNAs.
- This mechanism bypasses canonical pathways and defines minimal requirements for RISC assembly.
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