Cosuppression - Silencing of an endogenous gene caused by the introduction of a transgene or infection by a virus. This term, which can refer to silencing at the post-transcriptional (PTGS) or transcriptional (TGS) level, has been primarily adopted by researchers working with plants.
Post-transcriptional Gene Silencing (PTGS) - Silencing of an endogenous gene caused by the introduction of a homologous dsRNA, transgene or virus. In PTGS, the transcript of the silenced gene is synthesized but does not accumulate because it is rapidly degraded. This is a more general term than RNAi, since it can be triggered by several different means.
Quelling - PTGS in Neurospora crassa induced by the introduction of a transgene.
RISC - RNA-induced silencing complex. A nuclease complex, composed of proteins and siRNA (see below), that targets and destroys endogenous mRNAs complementary to the siRNA within the complex.
RNA interference (RNAi) - Post-transcriptional gene silencing (PTGS) induced by the direct introduction of dsRNA. The term "RNA interference" was first used by researchers studying C. elegans.
siRNAs - Small interfering RNAs. Current models of PTGS indicate that these 21-23 nucleotide dsRNAs mediate PTGS. Introduction of siRNAs can induce PTGS in mammalian cells. siRNAs are apparently produced in vivo by cleavage of dsRNA introduced directly or via a transgene or virus. Amplification by an RNA-dependent RNA polymerase (RdRP) may occur in some organisms. siRNAs are incorporated into the RNA-induced silencing complex (RISC), guiding the complex to the homologous endogenous mRNA where the complex cleaves the transcript.
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