MiRNA-like duplexes as RNAi triggers with improved specificity.

Juan G. Betancur,Yukihide Tomari,Mayuko Yoda

doi:10.3389/fgene.2012.00127

Abstract

siRNA duplexes, the most common triggers of RNA interference, are first loaded into an Argonaute (Ago) protein and then undergo unwinding via passenger strand cleavage, which requires the slicer activity of the Ago protein. In mammals, only Ago2 out of the four Ago proteins possesses such slicer activity. In contrast, miRNA/miRNA* duplexes often contain central mismatches that prevent slicer-dependent unwinding. Instead, mismatches in specific regions (seed and 3′-mid regions) promote efficient slicer-independent unwinding by any of the four mammalian Ago proteins. Both slicer-dependent and slicer-independent unwinding mechanisms produce guide-containing RNA-induced silencing complex (RISC), which silences target mRNAs by cleavage, translational repression, and/or deadenylation that leads to mRNA decay. In this review, we summarize our current knowledge of the RISC assembly pathways, and describe a simple method to rationally design artificial miRNA/miRNA*-like duplexes and highlight its benefits to reduce the unwanted “off-target” effects without compromising the specific target silencing activity.

Highlights

SMALL RNAs AND RNA-induced silencing complex (RISC) MicroRNAs and small interfering RNAs are the best-characterized small RNAs, which play crucial roles in post-transcriptional gene silencing. miRNAs are encoded in the genome and regulate various biological processes
Because small RNAs only act as guide molecules to direct RISC to target mRNAs in a sequencedependent manner, they can regulate the expression of their targets only after they form RISC
Each of the four mammalian Ago proteins can induce translational repression and/or deadenylation that leads to mRNA decay, but only Ago2 can endonucleolytically cleave target mRNAs when the sequence of the small RNA is extensively complementary to the target mRNA (Hutvagner and Simard, 2008; Carthew and Sontheimer, 2009; Ghildiyal and Zamore, 2009; Siomi and Siomi, 2009)

Summary

Introduction

SMALL RNAs AND RISC MicroRNAs (miRNAs) and small interfering RNAs (siRNAs) are the best-characterized small RNAs, which play crucial roles in post-transcriptional gene silencing. miRNAs are encoded in the genome and regulate various biological processes. Central mismatches (position 8–11 at guide strand) in small RNA duplexes are preferred for RISC loading in human Ago1–4.

Results

Conclusion