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Gene suppression through RNA interference occurs
at the posttranscriptionl level and involves mRNA degradation (Montgomery et
al., 1998; Ngo et al., 1998). In addition to playing a powerful role in creating
loss-of-function mutants, it probably also plays an essential role in protecting
the genome against instability caused by exogenous RNAs (eg. Viruses) (Kasschau
et al., 1998) and accumulation of transposons and repetitive sequences (Ketting
et al., 1999; Tabara et al., 1999; Hannnon GJ, 2002). Thus the vast nature of
RNA interference-like processes may encompass not only gene silencing phenomena
but also cellular programs for regulation of genes, inhibition of transposon
mobilization, and anti-viral mechanism in plants.
RNAi occurs through a
series of steps involving the generation of small interfering RNAs (siRNAs) in
vivo through the action of a specific RNAaseIII endonuclease Dicer. The
resulting siRNAs mediate the degradation of their complementary RNA by
association of the siRNA with a nuclease complex to form what is called the
RNA-induced silencing Complex (RISC). In the next step, an unwinding of the
siRNA occurs which activates RISC. It is the activated RISC that binds to the
target mRNA and finally leads to the loss of expression of the gene it coded
(Zamore et al., 2000).
The major hurdle to achieving RNAi in mammals was
that dsRNAs longer than 30 nucleotides activated defense mechanisms that
resulted in non-specific degradation of RNA transcripts and a general shutdown
of host cell protein synthesis (Williams, BR 1997). This obstacle was recently
overcome by using in vitro synthesized ~21 nucleotide siRNAs to mediate
gene-specific suppression in mammalian cells. These siRNAs are long enough to
cause gene suppression but not so long to cause interferon response to take
place (Elbashir et al., 2001;Calpen et al., 2001). Once these molecules were
identified, several DNA vector-based strategies were developed allowing use of
RNAi into mammalian cells. |
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siRNA Designer Program
Design
oligonucleotides for use with IMGENEX's plasmids. Our proprietary program
evaluates sequence data based on published design criteria, as well as predicted
secondary structure. The results are displayed, along with other potential
sequences.
IMGENEX Vector maps
Sequence
information on all IMGENEX plasmids
Recent publications
An
up-to-the-minute listing of publications using of RNA interference
Publications using pSuppressor
Vectors
Animated overview of
RNAi
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