Small interfering RNA
Small RNA interference, called RNA interference or silencing RNA short times (siRNA is), is the class of the length of 20 to 25 base pairs, double-stranded RNA molecules. The siRNA, but plays a role in many of the most prominent RNA interference (RNAi) pathway in combination with expression of a particular gene with a nucleotide sequence additional. For example, the formation mechanism of the chromatin structure of the genome, or as antiviral agents, the siRNA acts in RNAi related to the road. Complexity of these pathways has been elucidated only now.
first, its role in post-transcriptional gene silencing in plants (PTGS) was discovered by a group of David Baulcombe at the Sainsbury Laboratory in Norwich Hayate, it was reported in Science in 1999 siRNA. The synthetic siRNA, reported Thomas Tuschl et naturally, can induce an RNAi in mammalian cells immediately. This discovery has led to increased interest in the use of RNAi for drug development and biomedical research. Short ‘end is hydroxide and 3’ end phosphorylated 5 of the overhang of two nucleotides (usually 21-BP) double-stranded RNA (dsRNA) Dicer enzyme, siRNA from a small acute RNA month and siRNA long chain dsRNA siRNA is that it is possible in principle to have a well-defined structure, knock synthetic siRNA that any gene has a sequence complementary, is introduced by transfection: catalyzing the formation of. , SiRNA is an important tool for drug target validation in post-genomic era and gene function.
In rapidly dividing cells in particular, gene knockdown by transfection of unsatisfactory often exogenous siRNA, the effect is because is temporary only. This can be overcome by creating an expression vector Sirna. siRNA sequence is modified in order to introduce a short loop of chain between the two. Receiving the copy short hairpin RNA that can be processed into Sirna function of Dicer in the usual way of the shRNA. Small nuclear RNA (() snRNA is; For H1, U6 genes involved in splicing is a component of RNase RNase P of human) cassette transfer common use of RNA polymerase III promoter to induce transcription. It is theorized that it is processed by Dicer siRNA transcripts as a result. Recently, it was found that dsRNA is also, it is possible to activate gene expression mechanism is called RNAa or “RNA-induced gene activation” small. This can cause activation of the potent transcription have been shown to genes related dsRNA targeting the gene promoter. RNAa is, been demonstrated in human cells using called “small activating RNA” and (saRNAs), a synthetic dsRNA. It is unclear RNAa may or may not still remain in the other organisms present.
RNAi is therefore intersects the number of other routes, with respect to non-specific effects caused by the try siRNA, it is not surprising. Mammalian cells when it detects a double-stranded RNA, such as siRNA, he can as immune response and viral by-product, an error occurs. For regulating gene expression through imperfect complementary base pairs with the target mRNA interaction mainly Furthermore, micro-RNA to be structurally related, can lead to non-targeted introduction of siRNA is undesirable. Introduction of siRNA Many can for activation of the innate immune response, leading to a non-specific events too. Retinoic acid-inducible gene I also (RIG-I), may be included [Browse] is little evidence so far, but it shows that it is due to the activation of dsRNA PKR of sensor probably have. Induction of cytokines by (TLR7) receptor 7 Toll-like has also been described. Has become a micro-RNA siRNA promising one way to reduce the non-specific effect, . By leveraging should be able to achieve gene knockdown similar relatively low concentrations of siRNA the intrinsic pathway occurs, micro RNA is present in nature. This may be necessary to reduce the non-specific effect.
New guidance, is the subject of another use of siRNA as a gene knockdown tool. (From the point of view of siRNA acts like a miRNA) Sirna that lead to problems of interpretation of the toxicity and potential data, genes with incomplete complementarity, is down-regulated by carelessness here. However, this established design algorithms siRNA with an appropriate control experiments can be seen partially in some are prepared to generate a siRNA that target substantially freely. For example, genomic analysis of the whole expression can be checked by the microarray technology, using the algorithm for further processing. On agreement with siRNA 3’UTR region near the target gene, or long stretch of seven base position 2 on the road – 2006 paper, indicate the 6 from the laboratory of Dr. Khvorova.
Given the ability to knock down any gene essentially, RNAi via siRNA generates a great deal of interest in the biology of both basic and applied. There is an increase in RNAi large screen which is intended to identify the important genes in biological various routes. It also processes the disease, to be dependent on the activity of multiple genes, it is possible that blocking the activity of the gene by siRNA in some cases to obtain a therapeutic effect is expected. However, live animals in particular, the application of RNAi poses many challenges by siRNA for human. In the experiment, in a manner not yet understood, while others which shows the efficiency of different cell types show no (efficiency transfection example) Knockdown such cells few, siRNA is, siRNA Reacts well but shows knockdown stable.
Of siRNA, the second half of 2005 that are tolerated better (see Figure for age-related macular degeneration, known as AMD) phase treatment RNAi results in two studies my first It is reported, and has a suitable pharmacokinetic properties. The Phase 1 clinical trial, RNAi will be used in delivery in lipid nanoparticles 41 patients with advanced cancer metastasis to the liver. RNAi is targeted important two genes encoding proteins of the growth kinesin spindle protein (KSP) cancer cells, vascular endothelial growth factor (VEGF),. The results can demonstrate the clinical benefit such as cancer, was stable after regression of metastases in some patients or six months. Mechanical analysis of biopsy samples of the patients showed the presence of the RNAi construct certificate sample that it has reached the target molecules are given. The proof of concept studies, it may be effective for post-exposure prophylaxis in humans, non-human primate lethal dose of Zaire Ebola virus, the survival rate of 100% of the strains most deadly has been shown that siRNA Ebola oriented .