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Mol. Cells 2008; 26(3): 308-313

Published online September 30, 2008

© The Korean Society for Molecular and Cellular Biology

Cleavage of the Star Strand Facilitates Assembly of Some MicroRNAs into Ago2-containing Silencing Complexes in Mammals

Chanseok Shin

Abstract

In animals, microRNAs (miRNAs) and small interfering RNAs (siRNAs) repress expression of protein coding genes by assembling distinct RNA-induced silencing complexes (RISCs). It has previously been shown that passenger-strand cleavage is the predominant mechanism when siRNA duplexes are loaded into Argonaute2 (Ago2)-containing RISC, while an unwinding bypass mechanism is favored for miRNA duplexes with mismatches. Here I present experimental data indicating that some mammalian miRNAs are assembled into Ago2-containing RISC by cleaving their corresponding miRNA star strands. This phenomenon may depend on the secondary structure near the scissile phosphate of the miRNA duplex. In addition, I show that ATP is not required for star-strand cleavage in this process. Taken together, the data here provide insight into the miRNA-loading mechanisms in mammals.

Keywords Argonaute, microRNA, miRNA star-strand cleavage, passenger-strand cleavage, RISC

Article

Research Article

Mol. Cells 2008; 26(3): 308-313

Published online September 30, 2008

Copyright © The Korean Society for Molecular and Cellular Biology.

Cleavage of the Star Strand Facilitates Assembly of Some MicroRNAs into Ago2-containing Silencing Complexes in Mammals

Chanseok Shin

Abstract

In animals, microRNAs (miRNAs) and small interfering RNAs (siRNAs) repress expression of protein coding genes by assembling distinct RNA-induced silencing complexes (RISCs). It has previously been shown that passenger-strand cleavage is the predominant mechanism when siRNA duplexes are loaded into Argonaute2 (Ago2)-containing RISC, while an unwinding bypass mechanism is favored for miRNA duplexes with mismatches. Here I present experimental data indicating that some mammalian miRNAs are assembled into Ago2-containing RISC by cleaving their corresponding miRNA star strands. This phenomenon may depend on the secondary structure near the scissile phosphate of the miRNA duplex. In addition, I show that ATP is not required for star-strand cleavage in this process. Taken together, the data here provide insight into the miRNA-loading mechanisms in mammals.

Keywords: Argonaute, microRNA, miRNA star-strand cleavage, passenger-strand cleavage, RISC

Mol. Cells
Jan 31, 2023 Vol.46 No.1, pp. 1~67
COVER PICTURE
RNAs form diverse shapes and play multiple functions as central molecules of gene expression. In this special issue on RNA, seven minireviews illustrate how basic concepts and recent RNA biology findings are transformed into new and exciting RNA therapeutics.

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