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:: ''See also RNA interference'' Small interfering RNA (siRNA), sometimes known as short interfering RNA or silencing RNA, is a class of double-stranded RNA molecules, 20-25 base pairs in length. siRNA plays many roles, but it is most notable in the RNA interference (RNAi) pathway, where it interferes with the expression of specific genes with complementary nucleotide sequences. siRNA functions by causing mRNA to be broken down after transcription,〔(RNA Interference: Biology, Mechanism, and Applications )〕 resulting in no translation. siRNA also acts in RNAi-related pathways, e.g., as an antiviral mechanism or in shaping the chromatin structure of a genome. The complexity of these pathways is only now being elucidated. siRNAs and their role in post-transcriptional gene silencing (PTGS) in plants were first discovered by David Baulcombe's group at the Sainsbury Laboratory in Norwich, England and reported in ''Science'' in 1999. Thomas Tuschl and colleagues soon reported in ''Nature'' that synthetic siRNAs could induce RNAi in mammalian cells. This discovery led to a surge in interest in harnessing RNAi for biomedical research and drug development. ==Structure== siRNAs have a well-defined structure: a short (usually 20 to 24-bp) double-stranded RNA (dsRNA) with phosphorylated 5' ends and hydroxylated 3' ends with two overhanging nucleotides. The Dicer enzyme catalyzes production of siRNAs from long dsRNAs and small hairpin RNAs. siRNAs can also be introduced into cells by transfection. Since in principle any gene can be knocked down by a synthetic siRNA with a complementary sequence, siRNAs are an important tool for validating gene function and drug targeting in the post-genomic era. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Small interfering RNA」の詳細全文を読む スポンサード リンク
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