Target Discovery and Validation Reviews and Protocols

7
Genome-Wide Screening by Using Small-Interfering
RNA Expression Libraries
Sahohime Matsumoto, Makoto Miyagishi, and Kazunari Taira
Summary
RNA interference (RNAi) is an evolutionarily conserved phenomenon in which gene
expression is silenced by double-stranded RNA (dsRNA) in a sequence-specific manner. This
technology has the potential to affect all aspects of target discovery and validation. With the
completion of the human genome, it is now possible to design small-interfering RNA (siRNA)
libraries targeting every human gene. Specific siRNAs, libraries containing a pathway, gene
family, or gene set of interest, are expected to unsecure new targets in pathways of therapeutic
interest. Here, we highlight the potential of siRNA screens for target identification by using cellbased
assays.
Key Words: RNA interference; small-interfering RNA (siRNA) library; target discovery;
apoptosis; genomics.
1. Introduction
RNA interference (RNAi) is a phenomenon whereby double-stranded RNAs
(dsRNAs) induce the degradation of corresponding target mRNAs in a
sequence-specific manner (1,2). In this process, the dsRNAs are processed by
Dicer into approx 21–23 nucleotides (nt) with 2-nt 3′ overhangs, known as
small-interfering RNAs (siRNAs) (3). Subsequently, these siRNAs are incorporated
into a silencing complex called RNA-induced silencing complex (RISC)
(4), and the siRNA–RISC complexes recognize and cleave the target mRNA (5)
(Fig. 1). In somatic mammalian cells, long dsRNAs also induce nonspecific
effects, which are known as the interferon response (6). However, transfection
of siRNAs in mammalian cells can circumvent the interferon response and
From: Methods in Molecular Biology, vol. 360, Target Discovery and Validation Reviews and Protocols
Volume I, Emerging Strategies for Targets and Biomarker Discovery
Edited by: M. Sioud © Humana Press Inc., Totowa, NJ
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