A post-transcriptional gene silencing pathway in which small interfering RNAs (siRNAs) elicit silencing of specific target genes. siRNAs are 21-23 nucleotide RNA duplexes that are fully complementary to their target mRNA. siRNAs can be exported and act in other cells, including in germline cells. Once incorporated into a RNA-induced silencing complex (RISC), siRNAs can downregulate gene expression by either of two posttranscriptional mechanisms: endonucleolytic cleavage of the mRNA or mRNA translational repression. siRNAs are present in lower animals and plants, but not found in mammals; whereas miRNAs are present in all the animals and in plants.
siRNA-mediated PTGS