Community hub
Recent from talks
Knowledge base stats:
Talk channels stats:
Members stats:
Small interfering RNA
Small interfering RNA (siRNA), sometimes known as short interfering RNA or silencing RNA, is a class of double-stranded non-coding RNA molecules, typically 20–24 base pairs in length, similar to microRNA (miRNA), and operating within the RNA interference (RNAi) pathway. It interferes with the expression of specific genes with complementary nucleotide sequences by degrading messenger RNA (mRNA) after transcription, preventing translation. It was discovered in 1998 by Andrew Fire at the Carnegie Institution for Science in Washington, D.C. and Craig Mello at the University of Massachusetts in Worcester.
Naturally occurring siRNAs have a well-defined structure that is 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.
In 1998, Andrew Fire at Carnegie Institution for Science in Washington DC and Craig Mello at University of Massachusetts in Worcester discovered the RNAi mechanism while working on the gene expression in the nematode, Caenorhabditis elegans. They won the Nobel prize for their research with RNAi in 2006. siRNAs and their role in post-transcriptional gene silencing (PTGS) was discovered in plants 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. In 2001, the expression of a specific gene was successfully silenced by introducing chemically synthesized siRNA into mammalian cells (Tuschl et al.) These discoveries led to a surge in interest in harnessing RNAi for biomedical research and drug development. Significant developments in siRNA therapies have been made with both organic (carbon based) and inorganic (non-carbon based) nanoparticles, which have been successful in drug delivery to the brain, offering promising methods to deliver therapeutics into human subjects. However, human applications of siRNA have had significant limitations to its success. One of these being off-targeting. There is also a possibility that these therapies can trigger innate immunity. Animal models have not been successful in accurately representing the extent of this response in humans. Hence, studying the effects of siRNA therapies has been a challenge.
In recent years, siRNA therapies have been approved and new methods have been established to overcome these challenges. There are approved therapies available for commercial use and several currently in the pipeline waiting to get approval.
The mechanism by which natural siRNA causes gene silencing through repression of translation occurs as follows:
siRNA is also similar to miRNA, however, miRNAs are derived from shorter stemloop RNA products. miRNAs typically silence genes by repression of translation and have broader specificity of action, while siRNAs typically work with higher specificity by cleaving the mRNA before translation, with 100% complementarity.
Gene knockdown by transfection of exogenous siRNA is often unsatisfactory because the effect is only transient, especially in rapidly dividing cells. This may be overcome by creating an expression vector for the siRNA. The siRNA sequence is modified to introduce a short loop between the two strands. The resulting transcript is a short hairpin RNA (shRNA), which can be processed into a functional siRNA by Dicer in its usual fashion. Typical transcription cassettes use an RNA polymerase III promoter (e.g., U6 or H1) to direct the transcription of small nuclear RNAs (snRNAs) (U6 is involved in RNA splicing; H1 is the RNase component of human RNase P). It is theorized that the resulting siRNA transcript is then processed by Dicer.
The gene knockdown efficiency can also be improved by using cell squeezing.
Hub AI
Small interfering RNA AI simulator
(@Small interfering RNA_simulator)
Small interfering RNA
Small interfering RNA (siRNA), sometimes known as short interfering RNA or silencing RNA, is a class of double-stranded non-coding RNA molecules, typically 20–24 base pairs in length, similar to microRNA (miRNA), and operating within the RNA interference (RNAi) pathway. It interferes with the expression of specific genes with complementary nucleotide sequences by degrading messenger RNA (mRNA) after transcription, preventing translation. It was discovered in 1998 by Andrew Fire at the Carnegie Institution for Science in Washington, D.C. and Craig Mello at the University of Massachusetts in Worcester.
Naturally occurring siRNAs have a well-defined structure that is 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.
In 1998, Andrew Fire at Carnegie Institution for Science in Washington DC and Craig Mello at University of Massachusetts in Worcester discovered the RNAi mechanism while working on the gene expression in the nematode, Caenorhabditis elegans. They won the Nobel prize for their research with RNAi in 2006. siRNAs and their role in post-transcriptional gene silencing (PTGS) was discovered in plants 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. In 2001, the expression of a specific gene was successfully silenced by introducing chemically synthesized siRNA into mammalian cells (Tuschl et al.) These discoveries led to a surge in interest in harnessing RNAi for biomedical research and drug development. Significant developments in siRNA therapies have been made with both organic (carbon based) and inorganic (non-carbon based) nanoparticles, which have been successful in drug delivery to the brain, offering promising methods to deliver therapeutics into human subjects. However, human applications of siRNA have had significant limitations to its success. One of these being off-targeting. There is also a possibility that these therapies can trigger innate immunity. Animal models have not been successful in accurately representing the extent of this response in humans. Hence, studying the effects of siRNA therapies has been a challenge.
In recent years, siRNA therapies have been approved and new methods have been established to overcome these challenges. There are approved therapies available for commercial use and several currently in the pipeline waiting to get approval.
The mechanism by which natural siRNA causes gene silencing through repression of translation occurs as follows:
siRNA is also similar to miRNA, however, miRNAs are derived from shorter stemloop RNA products. miRNAs typically silence genes by repression of translation and have broader specificity of action, while siRNAs typically work with higher specificity by cleaving the mRNA before translation, with 100% complementarity.
Gene knockdown by transfection of exogenous siRNA is often unsatisfactory because the effect is only transient, especially in rapidly dividing cells. This may be overcome by creating an expression vector for the siRNA. The siRNA sequence is modified to introduce a short loop between the two strands. The resulting transcript is a short hairpin RNA (shRNA), which can be processed into a functional siRNA by Dicer in its usual fashion. Typical transcription cassettes use an RNA polymerase III promoter (e.g., U6 or H1) to direct the transcription of small nuclear RNAs (snRNAs) (U6 is involved in RNA splicing; H1 is the RNase component of human RNase P). It is theorized that the resulting siRNA transcript is then processed by Dicer.
The gene knockdown efficiency can also be improved by using cell squeezing.