My watch list

RNA interference

RNA interference (RNAi) is a mechanism that inhibits gene expression by causing the degradation of specific RNA molecules or hindering the transcription of specific genes. The targets are often RNA from viruses and transposons (probably a form of innate immune response), although it also plays a role in regulating development and genome maintenance. Key to the RNAi processes are small interfering RNA strands (siRNA), which have complementary nucleotide sequences to a targeted RNA strand. The siRNA "guides" proteins within the RNAi pathway to the targeted messenger RNA (mRNA) and "cleaves" them, breaking them down into smaller portions that can no longer be translated into protein. A type of RNA transcribed from the genome itself, miRNA, works in the same way.

The RNAi pathway is initiated by the enzyme dicer, which cleaves long, double-stranded RNA (dsRNA) molecules into short fragments of 20–25 base pairs. One of the two strands of each fragment, known as the guide strand, is then incorporated into the RNA-induced silencing complex (RISC) and pairs with complementary sequences. The most well-studied outcome of this recognition event is post-transcriptional gene silencing. This occurs when the guide strand specifically pairs with a mRNA molecule and induces the degradation by argonaute, the catalytic component of the RISC complex. Another outcome is epigenetic changes to a gene – histone modification and DNA methylation – affecting the degree the gene is transcribed.

The selective and robust effect of RNAi on gene expression makes it a valuable research tool, both in cell culture and in living organisms because synthetic dsRNA introduced into cells can induce suppression of specific genes of interest. RNAi may also be used for large-scale screens that systematically shut down each gene in the cell, which can help identify the components necessary for a particular cellular process or an event such as cell division. Exploitation of the pathway is also a promising tool in biotechnology and medicine.

Historically, RNA interference was known by other names, including post transcriptional gene silencing, transgene silencing, and quelling. Only after these apparently-unrelated processes were fully understood did it become clear that they all described the RNAi phenomenon. RNAi has also been confused with antisense suppression of gene expression, which does not act catalytically to degrade mRNA, but instead involves single-stranded RNA fragments physically binding to mRNA and blocking protein translation. In 2006, Andrew Fire and Craig C. Mello shared the Nobel Prize in Physiology or Medicine for their work on RNA interference in the nematode worm C. elegans,^[2] which they published in 1998.^[3]

Additional recommended knowledge

Daily Visual Balance Check

Don't let static charges disrupt your weighing accuracy

Safe Weighing Range Ensures Accurate Results

Cellular mechanism

RNAi is an RNA-dependent gene silencing process that is controlled by the RNA-induced silencing complex (RISC) and is initiated by short double-stranded RNA molecules in a cell's cytoplasm, where they interact with the catalytic RISC component argonaute. When the dsRNA is exogenous (coming from infection by a virus with an RNA genome or laboratory manipulations), the RNA is imported directly into the cytoplasm and cleaved to short fragments by the enzyme dicer. The initiating dsRNA can also be endogenous (originating in the cell), as in pre-microRNAs expressed from RNA-coding genes in the genome. The primary transcripts from such genes are first processed to form the characteristic stem-loop structure of pre-miRNA in the nucleus, then exported to the cytoplasm to be cleaved by dicer. Thus the two pathways for exogenous and endogenous dsRNA converge at the RISC complex, which mediates gene silencing effects.

dsRNA cleavage

Exogenous dsRNA initiates RNAi by activating the ribonuclease protein dicer,^[5] which binds and cleaves double-stranded RNAs (dsRNA)s to produce double-stranded fragments of 20–25 base pairs with a few unpaired overhang bases on each end.^[6]^[7] Bioinformatics studies on the genomes of multiple organisms suggest this length maximizes target-gene specificity and minimizes non-specific effects.^[8] These short double-stranded fragments are called small interfering RNAs (siRNAs). These siRNAs are then separated into single strands and integrated into an active RISC complex. After integration into the RISC, siRNAs base-pair to their target mRNA and induce cleavage of the mRNA, thereby preventing it from being used as a translation template.

Exogenous dsRNA is detected and bound by an effector protein, known as RDE-4 in C. elegans and R2D2 in Drosophila, that stimulates dicer activity.^[9] This protein only binds long dsRNAs, but the mechanism producing this length specificity is unknown.^[9] These RNA-binding proteins then facilitate transfer of cleaved siRNAs to the RISC complex.^[10]

This initiation pathway may be amplified by the cell through the synthesis of a population of 'secondary' siRNAs using the dicer-produced initiating or 'primary' siRNAs as templates.^[11] These siRNAs are structurally distinct from dicer-produced siRNAs and appear to be produced by an RNA-dependent RNA polymerase (RdRP).^[12]^[13]

microRNA

MicroRNAs (miRNAs) are genomically encoded non-coding RNAs that help regulate gene expression, particularly during development. The phenomenon of RNA interference, broadly defined, includes the endogenously induced gene silencing effects of miRNAs as well as silencing triggered by foreign dsRNA. Mature miRNAs are structurally similar to siRNAs produced from exogenous dsRNA, but before reaching maturity, miRNAs must first undergo extensive post-transcriptional modification. An miRNA is expressed from a much longer RNA-coding gene as a primary transcript known as a pri-miRNA, which is processed in the cell nucleus to a 70-nucleotide stem-loop structure called a pre-miRNA by the microprocessor complex. This complex consists of an RNase III enzyme called Drosha and a dsRNA-binding protein Pasha. The dsRNA portion of this pre-miRNA is bound and cleaved by dicer to produce the mature miRNA molecule that can be integrated into the RISC complex; thus, miRNA and siRNA share the same cellular machinery downstream of their initial processing.^[14]

The siRNAs derived from long dsRNA precursors differ from miRNAs in that miRNAs, especially those in animals, typically have incomplete base pairing to a target and inhibit the translation of many different mRNAs with similar sequences. In contrast, siRNAs typically base-pair perfectly and induce mRNA cleavage only in a single, specific target.^[15] In Drosophila and C. elegans, miRNA and siRNA are processed by distinct argonaute proteins and dicer enzymes.^[16]^[17]

RISC activation and catalysis

The active components of an RNA-induced silencing complex (RISC) are endonucleases called argonaute proteins, which cleave the target mRNA strand complementary to their bound siRNA. As the fragments produced by dicer are double-stranded, they could each in theory produce a functional siRNA. However, only one of the two strands, which is known as the guide strand, binds the argonaute protein and directs gene silencing. The other anti-guide strand or passenger strand is degraded during RISC activation.^[18] Although it was first believed that an ATP-dependent helicase separated these two strands,^[19] the process is actually ATP-independent and performed directly by the protein components of RISC.^[20]^[21] The strand selected as the guide tends to be that with a more stable 5' end, but strand selection is unaffected by the direction in which dicer cleaves the dsRNA before RISC incorporation.^[22] Instead, the R2D2 protein may serve as the differentiating factor by binding the less-stable 5' end of the passenger strand.^[23]

The structural basis for binding of RNA to the argonaute protein was examined by X-ray crystallography of the binding domain of an RNA-bound argonaute protein. Here, the phosphorylated 5' end of the RNA strand enters a conserved basic surface pocket and makes contacts through a divalent cation (an atom with two or more extra electrons) such as magnesium and by aromatic stacking (a process that allows more than one atom to share an electron by passing it back and forth) between the 5' nucleotide in the siRNA and a conserved tyrosine residue. This site is thought to form a nucleation site for the binding of the siRNA to its mRNA target.^[24]

It is not understood how the activated RISC complex locates complementary mRNAs within the cell. Although the cleavage process has been proposed to be linked to translation, translation of the mRNA target is not essential for RNAi-mediated degradation.^[25] Indeed, RNAi may be more effective against mRNA targets that are not translated.^[26] Argonaute proteins, the catalytic components of RISC, are localized to specific regions in the cytoplasm called P-bodies (also cytoplasmic bodies or GW bodies), which are regions with high rates of mRNA decay;^[27] miRNA activity is also clustered in P-bodies.^[28] The disruption of P bodies in cells decreases the efficiency of RNA interference, suggesting that they are the site of a critical step in the RNAi process.^[29]

Transcriptional silencing

Components of the RNA interference pathway are also used in many eukaryotes in the maintenance of the organisation and structure of their genomes. Modification of histones and associated induction of heterochromatin formation serves to downregulate genes pre-transcriptionally;^[30] this process is referred to as RNA-induced transcriptional silencing (RITS), and is carried out by a complex of proteins called the RITS complex. In fission yeast this complex contains argonaute, a chromodomain protein Chp1, and a protein called Tas3 of unknown function.^[31] As a consequence, the induction and spread of heterochromatic regions requires the argonaute and RdRP proteins.^[32] Indeed, deletion of these genes in the fission yeast S. pombe disrupts histone methylation and centromere formation,^[33] causing slow or stalled anaphase during cell division.^[34] In some cases, similar processes associated with histone modification have been observed to transcriptionally upregulate genes.^[35]

The mechanism by which the RITS complex induces heterochromatin formation and organization is not well understood, and most studies have focused on the mating-type region in fission yeast, which may not be representative of activities in other genomic regions or organisms. In maintenance of existing heterochromatin regions, RITS forms a complex with siRNAs complementary to the local genes and stably binds local methylated histones, acting co-transcriptionally to degrade any nascent pre-mRNA transcripts that are initiated by RNA polymerase. The formation of such a heterochromatin region, though not its maintenance, is dicer-dependent, presumably because dicer is required to generate the initial complement of siRNAs that target subsequent transcripts.^[36] Heterochromatin maintenance has been suggested to function as a self-reinforcing feedback loop, as new siRNAs are formed from the occasional nascent transcripts by RdRP for incorporation into local RITS complexes.^[37] The relevance of observations from fission yeast mating-type regions and centromeres to mammals is not clear, as heterochromatin maintenance in mammalian cells may be independent of the components of the RNAi pathway.^[38]

Variation among organisms

Organisms vary in their ability to take up foreign dsRNA and use it in the RNAi pathway. The effects of RNA interference can be both systemic and heritable in plants and C. elegans, although not in Drosophila or mammals. In plants, RNAi is thought to propagate by the transfer of siRNAs between cells through plasmodesmata (channels in the cell walls that enable communication and transport).^[19] The heritability comes from methylation of promoters targeted by RNAi; the new methylation pattern is copied in each new generation of the cell.^[40] A broad general distinction between plants and animals lies in the targeting of endogenously produced miRNAs; in plants, miRNAs are usually perfectly or nearly perfectly complementary to their target genes and induce direct mRNA cleavage by RISC, while animals' miRNAs tend to be more divergent in sequence and induce translational repression.^[39] This translational effect may be produced by inhibiting the interactions of translation initiation factors with the messenger RNA's polyadenine tail.^[41]

Some eukaryotic protozoa such as Leishmania major and Trypanosoma cruzi lack the RNAi pathway entirely.^[42]^[43] Most or all of the components are also missing in some fungi, most notably the model organism Saccharomyces cerevisiae.^[44] Certain ascomycetes and basidiomycetes are also missing RNA interference pathways; this observation indicates that proteins required for RNA silencing have been lost independently from many fungal lineages, possibly due to the evolution of a novel pathway with similar function, or to the lack of selective advantage in certain niches.^[45]

Related prokaryotic systems

Gene expression in prokaryotes is influenced by an RNA-based system similar in some respects to RNAi. Here, RNA-encoding genes control mRNA abundance or translation by producing a complementary RNA that binds to an mRNA by base pairing. However these regulatory RNAs are not generally considered to be analogous to miRNAs because the dicer enzyme is not involved.^[46] It has been suggested that CRISPR systems in prokaryotes are analogous to eukaryotic RNA interference systems, although none of the protein components are orthologous.^[47]

Biological functions

Immunity

RNA interference is a vital part of the immune response to viruses and other foreign genetic material, especially in plants where it may also prevent self-propagation by transposons.^[48] Plants such as Arabidopsis thaliana express multiple dicer homologs that are specialized to react differently when the plant is exposed to different types of viruses.^[49] Even before the RNAi pathway was fully understood, it was known that induced gene silencing in plants could spread throughout the plant in a systemic effect, and could be transferred from stock to scion plants via grafting.^[50] This phenomenon has since been recognized as a feature of the plant adaptive immune system, and allows the entire plant to respond to a virus after an initial localized encounter.^[51] In response, many plant viruses have evolved elaborate mechanisms that suppress the RNAi response in plant cells.^[52] These include viral proteins that bind short double-stranded RNA fragments with single-stranded overhang ends, such as those produced by the action of dicer.^[53] Some plant genomes also express endogenous siRNAs in response to infection by specific types of bacteria.^[54] These effects may be part of a generalized response to pathogens that downregulates any metabolic processes in the host that aid the infection process.^[55]

Although animals generally express fewer variants of the dicer enzyme than plants, RNAi in some animals has also been shown to produce an antiviral response. In both juvenile and adult Drosophila, RNA interference is important in antiviral innate immunity and is active against pathogens such as Drosophila X virus.^[56]^[57] A similar role in immunity may operate in C. elegans, as argonaute proteins are upregulated in response to viruses and worms that overexpress components of the RNAi pathway are resistant to viral infection.^[58]^[59]

The role of RNA interference in mammalian innate immunity is poorly understood, and relatively little data is available. However, the existence of viruses that encode genes able to suppress the RNAi response in mammalian cells may be evidence in favour of an RNAi-dependent mammalian immune response.^[60]^[61] However, this hypothesis of RNAi-mediated immunity in mammals has been challenged as poorly substantiated.^[62] Alternative functions for RNAi in mammalian viruses also exist, such as miRNAs expressed by the herpes virus that may act as heterochromatin organization triggers to mediate viral latency.^[35]

Downregulation of genes

Endogenously expressed miRNAs, including both intronic and intergenic miRNAs, are most important in translational repression^[39] and in the regulation of development, especially the timing of morphogenesis and the maintenance of undifferentiated or incompletely differentiated cell types such as stem cells.^[63] The role of endogenously expressed miRNA in downregulating gene expression was first described in C. elegans in 1993.^[64] In plants this function was discovered when the "JAW microRNA" of Arabidopsis was shown to be involved in the regulation of several genes that control plant shape.^[65] In plants, the majority of genes regulated by miRNAs are transcription factors;^[66] thus miRNA activity is particularly wide-ranging and regulates entire gene networks during development by modulating the expression of key regulatory genes, including transcription factors as well as F-box proteins.^[67] In many organisms, including humans, miRNAs have also been linked to the formation of tumors and dysregulation of the cell cycle. Here, miRNAs can function as both oncogenes and tumor suppressors.^[68]

Upregulation of genes

RNA sequences (siRNA and miRNA) that are complementary to parts of a promoter can increase gene transcription, a phenomenon dubbed RNA activation. As in gene silencing by RNA interference, Dicer and RISC are involved, but the mechanism for how RISC upregulates a gene is unknown.^[69]

Crosstalk with RNA editing

The type of RNA editing that is most prevalent in higher eukaryotes converts adenosine nucleotides into inosine in dsRNAs via the enzyme adenosine deaminase (ADAR).^[70] It was originally proposed in 2000 that the RNAi and A→I RNA editing pathways might compete for a common dsRNA substrate.^[71] Indeed, some pre-miRNAs do undergo A→I RNA editing,^[72]^[73] and this mechanism may regulate the processing and expression of mature miRNAs.^[73] Furthermore, at least one mammalian ADAR can sequester siRNAs from RNAi pathway components.^[74] Further support for this model comes from studies on ADAR-null C. elegans strains indicating that A→I RNA editing may counteract RNAi silencing of endogenous genes and transgenes.^[75]

Evolution

Based on parsimony-based phylogenetic analysis, the most recent common ancestor of all eukaryotes most likely already possessed an early RNA interference pathway; the absence of the pathway in certain eukaryotes is thought to be a derived characteristic. The ancestral RNAi system probably contained at least one dicer-like protein, one argonaute, one PIWI protein, and an RNA dependent RNA polymerase that may have also played other cellular roles.^[76] A large-scale comparative genomics study likewise indicates that the eukaryotic crown group already possessed these components, which may then have had closer functional associations with generalized RNA degradation systems such as the exosome.^[77] This study also suggests that the RNA-binding argonaute protein family, which is shared among eukaryotes, most archaea, and at least some bacteria (such as Aquifex aeolicus), is homologous to and originally evolved from components of the translation initiation system.

The ancestral function of the RNAi system is generally agreed to have been immune defense against exogenous genetic elements such as transposons and viral genomes.^[76]^[78] Related functions such as histone modification may have already been present in the ancestor of modern eukaryotes, although other functions such as regulation of development by miRNA are thought to have evolved later.^[76]

RNA interference genes, as components of the antiviral innate immune system in many eukaryotes, are involved in an evolutionary arms race with viral genes. Some viruses have evolved mechanisms for suppressing the RNAi response in their host cells, an effect that has been noted particularly for plant viruses.^[52] Studies of evolutionary rates in Drosophila have shown that genes in the RNAi pathway are subject to strong directional selection and are among the fastest-evolving genes in the Drosophila genome.^[79]

Technological applications

Gene knockdown

The RNA interference pathway is often exploited in experimental biology to study the function of genes in cell culture and in vivo in model organisms. Double-stranded RNA is synthesized with a sequence complementary to a gene of interest and introduced into a cell or organism, where it is recognized as exogenous genetic material and activates the RNAi pathway. Using this mechanism, researchers can cause a drastic decrease in the expression of a targeted gene. Studying the effects of this decrease can show the physiological role of the gene product. Since RNAi may not totally abolish expression of the gene, this technique is sometimes referred as a "knockdown", to distinguish it from "knockout" procedures in which expression of a gene is entirely eliminated.

Extensive efforts in computational biology have been directed toward the design of successful dsRNA reagents that maximize gene knockdown but minimize "off-target" effects. Off-target effects arise when an introduced RNA has a base sequence that can pair with and thus reduce the expression of multiple genes at a time. Such problems occur more frequently when the dsRNA contains repetitive sequences. It has been estimated from studying the genomes of H. sapiens, C. elegans, and S. pombe that about 10% of possible siRNAs will have substantial off-target effects.^[8] A multitude of software tools have been developed implementing algorithms for the design of general,^[81]^[82] mammal-specific,^[83] and virus-specific^[84] siRNAs that are automatically checked for possible cross-reactivity.

Depending on the organism and experimental system, the exogenous RNA may be a long strand designed to be cleaved by dicer, or short RNAs designed to serve as siRNA substrates. In most mammalian cells, shorter RNAs are used because long double-stranded RNA molecules induce the mammalian interferon response, a form of innate immunity that reacts nonspecifically to foreign genetic material.^[85] Mouse oocytes and cells from early mouse embryos lack this reaction to exogenous dsRNA and are therefore a common model system for studying gene-knockdown effects in mammals.^[86] Specialized laboratory techniques have also been developed to improve the utility of RNAi in mammalian systems by avoiding the direct introduction of siRNA, for example, by stable transfection with a plasmid encoding the appropriate sequence from which siRNAs can be transcribed,^[87] or by more elaborate lentiviral vector systems allowing the inducible activation or deactivation of transcription, known as conditional RNAi.^[88]^[89]

Functional genomics

Most functional genomics applications of RNAi in animals have used C. elegans^[90] and Drosophila,^[91] as these are the common model organisms in which RNAi is most effective. C. elegans is particularly useful for RNAi research for two reasons: firstly, the effects of the gene silencing are generally heritable, and secondly because delivery of the dsRNA is extremely simple. Through a mechanism whose details are poorly understood, bacteria such as E. coli that carry the desired dsRNA can be fed to the worms and will transfer their RNA payload to the worm via the intestinal tract. This "delivery by feeding" is just as effective at inducing gene silencing as more costly and time-consuming delivery methods, such as soaking the worms in dsRNA solution and injecting dsRNA into the gonads.^[92] Although delivery is more difficult in most other organisms, efforts are also underway to undertake large-scale genomic screening applications in cell culture with mammalian cells.^[93]

Approaches to the design of genome-wide RNAi libraries can require more sophistication than the design of a single siRNA for a defined set of experimental conditions. Artificial neural networks are frequently used to design siRNA libraries^[94] and to predict their likely efficiency at gene knockdown.^[95] Mass genomic screening is widely seen as a promising method for genome annotation and has triggered the development of high-throughput screening methods based on microarrays.^[96]^[97] However, the utility of these screens and the ability of techniques developed on model organisms to generalize to even closely-related species has been questioned, for example from C. elegans to related parasitic nematodes.^[98]^[99]

Functional genomics using RNAi is a particularly attractive technique for genomic mapping and annotation in plants because many plants are polyploid, which presents substantial challenges for more traditional genetic engineering methods. For example, RNAi has been successfully used for functional genomics studies in bread wheat (which is hexaploid)^[100] as well as more common plant model systems Arabidopsis and maize.^[101]

Medicine

It may be possible to exploit RNA interference in therapy. Although it is difficult to introduce long dsRNA strands into mammalian cells due to the interferon response, the use of short interfering RNA mimics has been more successful.^[102] Among the first applications to reach clinical trials were in the treatment of macular degeneration and respiratory syncytial virus,^[103] RNAi has also been shown to be effective in the reversal of induced liver failure in mouse models.^[104]

Other proposed clinical uses center on antiviral therapies, including the inhibition of viral gene expression in cancerous cells,^[105] knockdown of host receptors and coreceptors for HIV,^[106] the silencing of hepatitis A^[107] and hepatitis B genes,^[108] silencing of influenza gene expression,^[35] and inhibition of measles viral replication.^[109] Potential treatments for neurodegenerative diseases have also been proposed, with particular attention being paid to the polyglutamine diseases such as Huntington's disease.^[110] RNA interference is also often seen as a promising way to treat cancer by silencing genes differentially upregulated in tumor cells or genes involved in cell division.^[111]^[112] A key area of research in the use of RNAi for clinical applications is the development of a safe delivery method, which to date has involved mainly viral vector systems similar to those suggested for gene therapy.^[113]^[114]

Despite the proliferation of promising cell culture studies for RNAi-based drugs, some concern has been raised regarding the safety of RNA interference, especially the potential for "off-target" effects in which a gene with a coincidentally similar sequence to the targeted gene is also repressed.^[115] A computational genomics study estimated that the error rate of off-target interactions is about 10%.^[8] One major study of liver disease in mice led to high death rates in the experimental animals, suggested by researchers to be the result of "oversaturation" of the dsRNA pathway.^[116]

Biotechnology

RNA interference has been used for applications in biotechnology, particularly in the engineering of food plants that produce lower levels of natural plant toxins. Such techniques take advantage of the stable and heritable RNAi phenotype in plant stocks. For example, cotton seeds are rich in dietary protein but naturally contain the toxic terpenoid product gossypol, making them unsuitable for human consumption. RNAi has been used to produce cotton stocks whose seeds contain reduced levels of delta-cadinene synthase, a key enzyme in gossypol production, without affecting the enzyme's production in other parts of the plant, where gossypol is important in preventing damage from plant pests.^[117] Similar efforts have been directed toward the reduction of the cyanogenic natural product linamarin in cassava plants.^[118]

Although no plant products that use RNAi-based genetic engineering have yet passed the experimental stage, development efforts have successfully reduced the levels of allergens in tomato plants^[119] and decreased the precursors of likely carcinogens in tobacco plants.^[120] Other plant traits that have been engineered in the laboratory include the production of non-narcotic natural products by the opium poppy,^[121] resistance to common plant viruses,^[122] and fortification of plants such as tomatoes with dietary antioxidants.^[123] Previous commercial products, including the Flavr Savr tomato and two cultivars of ringspot-resistant papaya, were originally developed using antisense technology but likely exploited the RNAi pathway.^[124]^[125]

History and discovery

The discovery of RNAi was preceded first by observations of transcriptional inhibition by antisense RNA expressed in transgenic plants,^[127] and more directly by reports of unexpected outcomes in experiments performed by plant scientists in the U.S. and The Netherlands in the early 1990s.^[128] In an attempt to alter flower colors in petunias, researchers introduced additional copies of a gene encoding chalcone synthase, a key enzyme for flower pigmentation into petunia plants of normally pink or violet flower color. The overexpressed gene was expected to result in darker flowers, but instead produced less pigmented, fully or partially white flowers, indicating that the activity of chalcone synthase had been substantially decreased; in fact, both the endogenous genes and the transgenes were downregulated in the white flowers. Soon after, a related event termed quelling was noted in the fungus Neurospora crassa,^[129] although it was not immediately recognized as related. Further investigation of the phenomenon in plants indicated that the downregulation was due to post-transcriptional inhibition of gene expression via an increased rate of mRNA degradation.^[130] This phenomenon was called co-suppression of gene expression, but the molecular mechanism remained unknown.

Not long after, plant virologists working on improving plant resistance to viral diseases observed a similar unexpected phenomenon. While it was known that plants expressing virus-specific proteins showed enhanced tolerance or resistance to viral infection, it was not expected that plants carrying only short, non-coding regions of viral RNA sequences would show similar levels of protection. Researchers believed that viral RNA produced by transgenes could also inhibit viral replication.^[131] The reverse experiment, in which short sequences of plant genes were introduced into viruses, showed that the targeted gene was suppressed in an infected plant. This phenomenon was labeled "virus-induced gene silencing" (VIGS), and the set of such phenomena were collectively called post transcriptional gene silencing.^[132]

After these initial observations in plants, many laboratories around the world searched for the occurrence of this phenomenon in other organisms.^[133]^[134] Craig C. Mello and Andrew Fire's 1998 Nature paper reported a potent gene silencing effect after injecting double stranded RNA into C. elegans.^[3] In investigating the regulation of muscle protein production, they observed that neither mRNA nor antisense RNA injections had an effect on protein production, but double-stranded RNA successfully silenced the targeted gene. As a result of this work, they coined the term RNAi. Fire and Mello's discovery was particularly notable because it represented the first identification of the causative agent for the phenomenon. Fire and Mello were awarded the Nobel Prize in Physiology or Medicine in 2006 for their work.^[2]

References

^ Hammond S, Bernstein E, Beach D, Hannon G (2000). "An RNA-directed nuclease mediates post-transcriptional gene silencing in Drosophila cells". Nature 404 (6775): 293-6. PMID 10749213.
^ ^a ^b Daneholt, Bertil. Advanced Information: RNA interference. The Nobel Prize in Physiology or Medicine 2006. Retrieved on 2007-01-25.
^ ^a ^b Fire A, Xu S, Montgomery M, Kostas S, Driver S, Mello C (1998). "Potent and specific genetic interference by double-stranded RNA in Caenorhabditis elegans". Nature 391 (6669): 806-11. PMID 9486653.
^ Macrae I, Zhou K, Li F, Repic A, Brooks A, Cande W, Adams P, Doudna J (2006). "Structural basis for double-stranded RNA processing by dicer". Science 311 (5758): 195–8. PMID 16410517.
^ Bernstein E, Caudy A, Hammond S, Hannon G (2001). "Role for a bidentate ribonuclease in the initiation step of RNA interference". Nature 409 (6818): 363-6. PMID 11201747.
^ Zamore P, Tuschl T, Sharp P, Bartel D (2000). "RNAi: double-stranded RNA directs the ATP-dependent cleavage of mRNA at 21 to 23 nucleotide intervals". Cell 101 (1): 25–33. PMID 10778853.
^ Vermeulen A, Behlen L, Reynolds A, Wolfson A, Marshall W, Karpilow J, Khvorova A (2005). "The contributions of dsRNA structure to dicer specificity and efficiency". RNA 11 (5): 674-82. PMID 15811921.
^ ^a ^b ^c Qiu S, Adema C, Lane T (2005). "A computational study of off-target effects of RNA interference". Nucleic Acids Res 33 (6): 1834–47. PMID 15800213.
^ ^a ^b Parker G, Eckert D, Bass B (2006). "RDE-4 preferentially binds long dsRNA and its dimerization is necessary for cleavage of dsRNA to siRNA". RNA 12 (5): 807-18. PMID 16603715.
^ Liu Q, Rand T, Kalidas S, Du F, Kim H, Smith D, Wang X (2003). "R2D2, a bridge between the initiation and effector steps of the Drosophila RNAi pathway". Science 301 (5641): 1921–5. PMID 14512631.
^ Baulcombe D (2007). "Molecular biology. Amplified silencing". Science 315 (5809): 199–200. PMID 17218517.
^ Pak J, Fire A (2007). "Distinct populations of primary and secondary effectors during RNAi in C. elegans". Science 315 (5809): 241-4. PMID 17124291.
^ Sijen T, Steiner F, Thijssen K, Plasterk R (2007). "Secondary siRNAs result from unprimed RNA synthesis and form a distinct class". Science 315 (5809): 244-7. PMID 17158288.
^ Gregory R, Chendrimada T, Shiekhattar R (2006). "MicroRNA biogenesis: isolation and characterization of the microprocessor complex". Methods Mol Biol 342: 33–47. PMID 16957365.
^ Pillai RS, Bhattacharyya SN, Filipowicz W. "Repression of protein synthesis by miRNAs: how many mechanisms?". Trends Cell Biol. PMID 17197185.
^ Okamura K, Ishizuka A, Siomi H, Siomi M (2004). "Distinct roles for Argonaute proteins in small RNA-directed RNA cleavage pathways". Genes Dev 18 (14): 1655–66. PMID 15231716.
^ Lee Y, Nakahara K, Pham J, Kim K, He Z, Sontheimer E, Carthew R (2004). "Distinct roles for Drosophila Dicer-1 and Dicer-2 in the siRNA/miRNA silencing pathways". Cell 117 (1): 69–81. PMID 15066283.
^ Gregory R, Chendrimada T, Cooch N, Shiekhattar R (2005). "Human RISC couples microRNA biogenesis and posttranscriptional gene silencing". Cell 123 (4): 631-40. PMID 16271387.
^ ^a ^b (2004) Molecular Cell Biology, 5th ed., WH Freeman: New York, NY. ISBN 978-0716743668.
^ Matranga C, Tomari Y, Shin C, Bartel D, Zamore P (2005). "Passenger-strand cleavage facilitates assembly of siRNA into Ago2-containing RNAi enzyme complexes". Cell 123 (4): 607-20. PMID 16271386.
^ Leuschner P, Ameres S, Kueng S, Martinez J (2006). "Cleavage of the siRNA passenger strand during RISC assembly in human cells". EMBO Rep 7 (3): 314-20. PMID 16439995.
^ Preall J, He Z, Gorra J, Sontheimer E (2006). "Short interfering RNA strand selection is independent of dsRNA processing polarity during RNAi in Drosophila". Curr Biol 16 (5): 530–5. PMID 16527750.
^ Tomari Y, Matranga C, Haley B, Martinez N, Zamore P (2004). "A protein sensor for siRNA asymmetry". Science 306 (5700): 1377–80. PMID 15550672.
^ Ma J, Yuan Y, Meister G, Pei Y, Tuschl T, Patel D (2005). "Structural basis for 5'-end-specific recognition of guide RNA by the A. fulgidus Piwi protein". Nature 434 (7033): 666-70. PMID 15800629.
^ Sen G, Wehrman T, Blau H (2005). "mRNA translation is not a prerequisite for small interfering RNA-mediated mRNA cleavage". Differentiation 73 (6): 287-93. PMID 16138829.
^ Gu S, Rossi J (2005). "Uncoupling of RNAi from active translation in mammalian cells". RNA 11 (1): 38–44. PMID 15574516.
^ Sen G, Blau H (2005). "Argonaute 2/RISC resides in sites of mammalian mRNA decay known as cytoplasmic bodies". Nat Cell Biol 7 (6): 633-6. PMID 15908945.
^ Lian S, Jakymiw A, Eystathioy T, Hamel J, Fritzler M, Chan E (2006). "GW bodies, microRNAs and the cell cycle". Cell Cycle 5 (3): 242-5. PMID 16418578.
^ Jakymiw A, Lian S, Eystathioy T, Li S, Satoh M, Hamel J, Fritzler M, Chan E (2005). "Disruption of P bodies impairs mammalian RNA interference". Nat Cell Biol 7 (12): 1267–74. PMID 16284622.
^ Holmquist G, Ashley T (2006). "Chromosome organization and chromatin modification: influence on genome function and evolution". Cytogenet Genome Res 114 (2): 96–125. PMID 16825762.
^ Verdel A, Jia S, Gerber S, Sugiyama T, Gygi S, Grewal S, Moazed D (2004). "RNAi-mediated targeting of heterochromatin by the RITS complex". Science 303 (5658): 672–6. PMID 14704433.
^ Irvine D, Zaratiegui M, Tolia N, Goto D, Chitwood D, Vaughn M, Joshua-Tor L, Martienssen R (2006). "Argonaute slicing is required for heterochromatic silencing and spreading". Science 313 (5790): 1134–7. PMID 16931764.
^ Volpe T, Kidner C, Hall I, Teng G, Grewal S, Martienssen R (2002). "Regulation of heterochromatic silencing and histone H3 lysine-9 methylation by RNAi". Science 297 (5588): 1833–7. PMID 12193640.
^ Volpe T, Schramke V, Hamilton G, White S, Teng G, Martienssen R, Allshire R (2003). "RNA interference is required for normal centromere function in fission yeast". Chromosome Res 11 (2): 137-46. PMID 12733640.
^ ^a ^b ^c Li LC, Okino ST, Zhao H, Pookot D, Place RF, Urakami S, Enokida H, Dahiya R. (2006). Small dsRNAs induce transcriptional activation in human cells. Proc Natl Acad Sci USA 103(46):17337-42. PMID 17085592
^ Noma K, Sugiyama T, Cam H, Verdel A, Zofall M, Jia S, Moazed D, Grewal S (2004). "RITS acts in cis to promote RNA interference-mediated transcriptional and post-transcriptional silencing". Nat Genet 36 (11): 1174–80. PMID 15475954.
^ Sugiyama T, Cam H, Verdel A, Moazed D, Grewal S (2005). "RNA-dependent RNA polymerase is an essential component of a self-enforcing loop coupling heterochromatin assembly to siRNA production". Proc Natl Acad Sci U S A 102 (1): 152-7. PMID 15615848.
^ Wang F, Koyama N, Nishida H, Haraguchi T, Reith W, Tsukamoto T (2006). "The assembly and maintenance of heterochromatin initiated by transgene repeats are independent of the RNA interference pathway in mammalian cells". Mol Cell Biol 26 (11): 4028–40. PMID 16705157.
^ ^a ^b ^c Saumet A, Lecellier CH (2006). "Anti-viral RNA silencing: do we look like plants?". Retrovirology 3 (3). PMID 16409629.
^ Jones L, Ratcliff F, Baulcombe DC (2001). "RNA-directed transcriptional gene silencing in plants can be inherited independently of the RNA trigger and requires Met1 for maintenance". Current Biology 11 (10): 747–757.
^ Humphreys DT, Westman BJ, Martin DI, Preiss T (2005). "MicroRNAs control translation initiation by inhibiting eukaryotic initiation factor 4E/cap and poly(A) tail function.". Proc Natl Acad Sci U S A 102: 16961–16966. PMID 16287976.
^ DaRocha W, Otsu K, Teixeira S, Donelson J (2004). "Tests of cytoplasmic RNA interference (RNAi) and construction of a tetracycline-inducible T7 promoter system in Trypanosoma cruzi". Mol Biochem Parasitol 133 (2): 175-86. PMID 14698430.
^ Robinson K, Beverley S (2003). "Improvements in transfection efficiency and tests of RNA interference (RNAi) approaches in the protozoan parasite Leishmania". Mol Biochem Parasitol 128 (2): 217-28. PMID 12742588.
^ L. Aravind, Hidemi Watanabe, David J. Lipman, and Eugene V. Koonin (2000). "Lineage-specific loss and divergence of functionally linked genes in eukaryotes". Procedings of the National Academy of Sciences 97 (21): 11319–11324.
^ Nakayashiki H, Kadotani N, Mayama S (2006). "Evolution and diversification of RNA silencing proteins in fungi". J Mol Evol 63 (1): 127-35. PMID 16786437.
^ Morita T, Mochizuki Y, Aiba H (2006). "Translational repression is sufficient for gene silencing by bacterial small noncoding RNAs in the absence of mRNA destruction". Proc Natl Acad Sci U S A 103 (13): 4858–63. PMID 16549791.
^ Makarova K, Grishin N, Shabalina S, Wolf Y, Koonin E (2006). "A putative RNA-interference-based immune system in prokaryotes: computational analysis of the predicted enzymatic machinery, functional analogies with eukaryotic RNAi, and hypothetical mechanisms of action". Biol Direct 1: 7. PMID 16545108.
^ Stram Y, Kuzntzova L (2006). "Inhibition of viruses by RNA interference". Virus Genes 32 (3): 299–306. PMID 16732482.
^ Blevins T, Rajeswaran R, Shivaprasad P, Beknazariants D, Si-Ammour A, Park H, Vazquez F, Robertson D, Meins F, Hohn T, Pooggin M (2006). "Four plant Dicers mediate viral small RNA biogenesis and DNA virus induced silencing". Nucleic Acids Res 34 (21): 6233–46. PMID 17090584.
^ Palauqui J, Elmayan T, Pollien J, Vaucheret H (1997). "Systemic acquired silencing: transgene-specific post-transcriptional silencing is transmitted by grafting from silenced stocks to non-silenced scions". EMBO J 16 (15): 4738–45. PMID 9303318.
^ Voinnet O (2001). "RNA silencing as a plant immune system against viruses". Trends Genet 17 (8): 449-59. PMID 11485817.
^ ^a ^b Lucy A, Guo H, Li W, Ding S (2000). "Suppression of post-transcriptional gene silencing by a plant viral protein localized in the nucleus". EMBO J 19 (7): 1672–80. PMID 10747034.
^ Mérai Z, Kerényi Z, Kertész S, Magna M, Lakatos L, Silhavy D (2006). "Double-stranded RNA binding may be a general plant RNA viral strategy to suppress RNA silencing". J Virol 80 (12): 5747–56. PMID 16731914.
^ Katiyar-Agarwal S, Morgan R, Dahlbeck D, Borsani O, Villegas A, Zhu J, Staskawicz B, Jin H (2006). "A pathogen-inducible endogenous siRNA in plant immunity". Proc Natl Acad Sci U S A 103 (47): 18002-7. PMID 17071740.
^ Fritz J, Girardin S, Philpott D (2006). "Innate immune defense through RNA interference". Sci STKE 2006 (339): pe27. PMID 16772641.
^ Zambon R, Vakharia V, Wu L (2006). "RNAi is an antiviral immune response against a dsRNA virus in Drosophila melanogaster". Cell Microbiol 8 (5): 880-9. PMID 16611236.
^ Wang X, Aliyari R, Li W, Li H, Kim K, Carthew R, Atkinson P, Ding S (2006). "RNA interference directs innate immunity against viruses in adult Drosophila". Science 312 (5772): 452-4. PMID 16556799.
^ Lu R, Maduro M, Li F, Li H, Broitman-Maduro G, Li W, Ding S (2005). "Animal virus replication and RNAi-mediated antiviral silencing in Caenorhabditis elegans". Nature 436 (7053): 1040–3. PMID 16107851.
^ Wilkins C, Dishongh R, Moore S, Whitt M, Chow M, Machaca K (2005). "RNA interference is an antiviral defence mechanism in Caenorhabditis elegans". Nature 436 (7053): 1044–7. PMID 16107852.
^ Berkhout B, Haasnoot J (2006). "The interplay between virus infection and the cellular RNA interference machinery". FEBS Lett 580 (12): 2896-902. PMID 16563388.
^ Schütz S, Sarnow P (2006). "Interaction of viruses with the mammalian RNA interference pathway". Virology 344 (1): 151-7. PMID 16364746.
^ Cullen B (2006). "Is RNA interference involved in intrinsic antiviral immunity in mammals?". Nat Immunol 7 (6): 563-7. PMID 16715068.
^ Carrington J, Ambros V (2003). "Role of microRNAs in plant and animal development". Science 301 (5631): 336-8. PMID 12869753.
^ Lee R, Feinbaum R, Ambros V (1993). "The C. elegans heterochronic gene lin-4 encodes small RNAs with antisense complementarity to lin-14". Cell 75 (5): 843-54. PMID 8252621.
^ Palatnik J, Allen E, Wu X, Schommer C, Schwab R, Carrington J, Weigel D (2003). "Control of leaf morphogenesis by microRNAs". Nature 425 (6955): 257-63. PMID 12931144.
^ Zhang B, Pan X, Cobb G, Anderson T (2006). "Plant microRNA: a small regulatory molecule with big impact". Dev Biol 289 (1): 3–16. PMID 16325172.
^ Jones-Rhoades M, Bartel D, Bartel B (2006). "MicroRNAS and their regulatory roles in plants". Annu Rev Plant Biol 57: 19–53. PMID 16669754.
^ Zhang B, Pan X, Cobb G, Anderson T (2007). "microRNAs as oncogenes and tumor suppressors". Dev Biol 302 (1): 1–12. PMID 16989803.
^ Check E (2007). "RNA interference: hitting the on switch". Nature 448 (7156): 855–858. PMID 17713502.
^ Bass B (2002). "RNA editing by adenosine deaminases that act on RNA". Annu Rev Biochem 71: 817-46. PMID 12045112.
^ Bass B (2000). "Double-stranded RNA as a template for gene silencing". Cell 101 (3): 235-8. PMID 10847677.
^ Luciano D, Mirsky H, Vendetti N, Maas S (2004). "RNA editing of a miRNA precursor". RNA 10 (8): 1174–7. PMID 15272117.
^ ^a ^b Yang W, Chendrimada T, Wang Q, Higuchi M, Seeburg P, Shiekhattar R, Nishikura K (2006). "Modulation of microRNA processing and expression through RNA editing by ADAR deaminases". Nat Struct Mol Biol 13 (1): 13–21. PMID 16369484.
^ Yang W, Wang Q, Howell K, Lee J, Cho D, Murray J, Nishikura K (2005). "ADAR1 RNA deaminase limits short interfering RNA efficacy in mammalian cells". J Biol Chem 280 (5): 3946–53. PMID 15556947.
^ Nishikura K (2006). "Editor meets silencer: crosstalk between RNA editing and RNA interference". Nat Rev Mol Cell Biol 7 (12): 919-31. PMID 17139332.
^ ^a ^b ^c Cerutti H, Casas-Mollano J (2006). "On the origin and functions of RNA-mediated silencing: from protists to man". Curr Genet 50 (2): 81–99. PMID 16691418.
^ Anantharaman V, Koonin E, Aravind L (2002). "Comparative genomics and evolution of proteins involved in RNA metabolism". Nucleic Acids Res 30 (7): 1427–64. PMID 11917006.
^ Buchon N, Vaury C (2006). "RNAi: a defensive RNA-silencing against viruses and transposable elements". Heredity 96 (2): 195–202. PMID 16369574.
^ Obbard D, Jiggins F, Halligan D, Little T (2006). "Natural selection drives extremely rapid evolution in antiviral RNAi genes". Curr Biol 16 (6): 580-5. PMID 16546082.
^ Brock T, Browse J, Watts J (2006). "Genetic regulation of unsaturated fatty acid composition in C. elegans". PLoS Genet 2 (7): e108. PMID 16839188.
^ Naito Y, Yamada T, Matsumiya T, Ui-Tei K, Saigo K, Morishita S (2005). "dsCheck: highly sensitive off-target search software for double-stranded RNA-mediated RNA interference". Nucleic Acids Res 33 (Web Server issue): W589-91. PMID 15980542.
^ Henschel A, Buchholz F, Habermann B (2004). "DEQOR: a web-based tool for the design and quality control of siRNAs". Nucleic Acids Res 32 (Web Server issue): W113-20. PMID 15215362.
^ Naito Y, Yamada T, Ui-Tei K, Morishita S, Saigo K (2004). "siDirect: highly effective, target-specific siRNA design software for mammalian RNA interference". Nucleic Acids Res 32 (Web Server issue): W124-9. PMID 15215364.
^ Naito Y, Ui-Tei K, Nishikawa T, Takebe Y, Saigo K (2006). "siVirus: web-based antiviral siRNA design software for highly divergent viral sequences". Nucleic Acids Res 34 (Web Server issue): W448-50. PMID 16845046.
^ Reynolds A, Anderson E, Vermeulen A, Fedorov Y, Robinson K, Leake D, Karpilow J, Marshall W, Khvorova A (2006). "Induction of the interferon response by siRNA is cell type- and duplex length-dependent". RNA 12 (6): 988-93. PMID 16611941.
^ Stein P, Zeng F, Pan H, Schultz R (2005). "Absence of non-specific effects of RNA interference triggered by long double-stranded RNA in mouse oocytes". Dev Biol 286 (2): 464-71. PMID 16154556.
^ Brummelkamp T, Bernards R, Agami R (2002). "A system for stable expression of short interfering RNAs in mammalian cells". Science 296 (5567): 550-3. PMID 11910072.
^ Tiscornia G, Tergaonkar V, Galimi F, Verma I (2004). "CRE recombinase-inducible RNA interference mediated by lentiviral vectors". Proc Natl Acad Sci U S A 101 (19): 7347–51. PMID 15123829.
^ Ventura A, Meissner A, Dillon C, McManus M, Sharp P, Van Parijs L, Jaenisch R, Jacks T (2004). "Cre-lox-regulated conditional RNA interference from transgenes". Proc Natl Acad Sci U S A 101 (28): 10380-5. PMID 15240889.
^ Kamath R, Ahringer J (2003). "Genome-wide RNAi screening in Caenorhabditis elegans". Methods 30 (4): 313-21. PMID 12828945.
^ Boutros M, Kiger A, Armknecht S, Kerr K, Hild M, Koch B, Haas S, Paro R, Perrimon N (2004). "Genome-wide RNAi analysis of growth and viability in Drosophila cells". Science 303 (5659): 832-5. PMID 14764878.
^ Fortunato A, Fraser A (2005). "Uncover genetic interactions in Caenorhabditis elegans by RNA interference". Biosci Rep 25 (5–6): 299–307. PMID 16307378.
^ Cullen L, Arndt G (2005). "Genome-wide screening for gene function using RNAi in mammalian cells". Immunol Cell Biol 83 (3): 217-23. PMID 15877598.
^ Huesken D, Lange J, Mickanin C, Weiler J, Asselbergs F, Warner J, Meloon B, Engel S, Rosenberg A, Cohen D, Labow M, Reinhardt M, Natt F, Hall J (2005). "Design of a genome-wide siRNA library using an artificial neural network". Nat Biotechnol 23 (8): 995–1001. PMID 16025102.
^ Ge G, Wong G, Luo B (2005). "Prediction of siRNA knockdown efficiency using artificial neural network models". Biochem Biophys Res Commun 336 (2): 723-8. PMID 16153609.
^ Janitz M, Vanhecke D, Lehrach H (2006). "High-throughput RNA interference in functional genomics". Handb Exp Pharmacol: 97–104. PMID 16594612.
^ Vanhecke D, Janitz M (2005). "Functional genomics using high-throughput RNA interference". Drug Discov Today 10 (3): 205-12. PMID 15708535.
^ Geldhof P, Murray L, Couthier A, Gilleard J, McLauchlan G, Knox D, Britton C (2006). "Testing the efficacy of RNA interference in Haemonchus contortus". Int J Parasitol 36 (7): 801-10. PMID 16469321.
^ Geldhof P, Visser A, Clark D, Saunders G, Britton C, Gilleard J, Berriman M, Knox D. (2007). "RNA interference in parasitic helminths: current situation, potential pitfalls and future prospects". Parasitology: 1–11. PMID 17201997.
^ Travella S, Klimm T, Keller B (2006). "RNA interference-based gene silencing as an efficient tool for functional genomics in hexaploid bread wheat". Plant Physiol 142 (1): 6–20. PMID 16861570.
^ McGinnis K, Chandler V, Cone K, Kaeppler H, Kaeppler S, Kerschen A, Pikaard C, Richards E, Sidorenko L, Smith T, Springer N, Wulan T (2005). "Transgene-induced RNA interference as a tool for plant functional genomics". Methods Enzymol 392: 1–24. PMID 15644172.
^ Paddison P, Caudy A, Hannon G (2002). "Stable suppression of gene expression by RNAi in mammalian cells". Proc Natl Acad Sci U S A 99 (3): 1443–8. PMID 11818553.
^ Sah D (2006). "Therapeutic potential of RNA interference for neurological disorders". Life Sci 79 (19): 1773–80. PMID 16815477.
^ Zender L, Hutker S, Liedtke C, Tillmann H, Zender S, Mundt B, Waltemathe M, Gosling T, Flemming P, Malek N, Trautwein C, Manns M, Kuhnel F, Kubicka S (2003). "Caspase 8 small interfering RNA prevents acute liver failure in mice". Proc Natl Acad Sci U S A 100 (13): 7797-802. PMID 12810955.
^ Jiang M, Milner J (2002). "Selective silencing of viral gene expression in HPV-positive human cervical carcinoma cells treated with siRNA, a primer of RNA interference". Oncogene 21 (39): 6041–8. PMID 12203116.
^ http://www.medscape.com/viewarticle/467320
^ Kusov Y, Kanda T, Palmenberg A, Sgro J, Gauss-Müller V (2006). "Silencing of hepatitis A virus infection by small interfering RNAs". J Virol 80 (11): 5599-610. PMID 16699041.
^ Jia F, Zhang Y, Liu C (2006). "A retrovirus-based system to stably silence hepatitis B virus genes by RNA interference". Biotechnol Lett 28 (20): 1679–85. PMID 16900331.
^ Hu L, Wang Z, Hu C, Liu X, Yao L, Li W, Qi Y (2005). "Inhibition of Measles virus multiplication in cell culture by RNA interference". Acta Virol 49 (4): 227-34. PMID 16402679.
^ Raoul C, Barker S, Aebischer P (2006). "Viral-based modelling and correction of neurodegenerative diseases by RNA interference". Gene Ther 13 (6): 487-95. PMID 16319945.
^ Putral L, Gu W, McMillan N (2006). "RNA interference for the treatment of cancer". Drug News Perspect 19 (6): 317-24. PMID 16971967.
^ Izquierdo M (2005). "Short interfering RNAs as a tool for cancer gene therapy". Cancer Gene Ther 12 (3): 217-27. PMID 15550938.
^ Li C, Parker A, Menocal E, Xiang S, Borodyansky L, Fruehauf J (2006). "Delivery of RNA interference". Cell Cycle 5 (18): 2103–9. PMID 16940756.
^ Takeshita F, Ochiya T (2006). "Therapeutic potential of RNA interference against cancer". Cancer Sci 97 (8): 689-96. PMID 16863503.
^ Tong A, Zhang Y, Nemunaitis J (2005). "Small interfering RNA for experimental cancer therapy". Curr Opin Mol Ther 7 (2): 114-24. PMID 15844618.
^ Grimm D, Streetz K, Jopling C, Storm T, Pandey K, Davis C, Marion P, Salazar F, Kay M (2006). "Fatality in mice due to oversaturation of cellular microRNA/short hairpin RNA pathways". Nature 441 (7092): 537-41. PMID 16724069.
^ Sunilkumar G, Campbell L, Puckhaber L, Stipanovic R, Rathore K (2006). "Engineering cottonseed for use in human nutrition by tissue-specific reduction of toxic gossypol". Proc Natl Acad Sci U S A 103 (48): 18054-9. PMID 17110445.
^ Siritunga D, Sayre R (2003). "Generation of cyanogen-free transgenic cassava". Planta 217 (3): 367-73. PMID 14520563.
^ Le L, Lorenz Y, Scheurer S, Fötisch K, Enrique E, Bartra J, Biemelt S, Vieths S, Sonnewald U (2006). "Design of tomato fruits with reduced allergenicity by dsRNAi-mediated inhibition of ns-LTP (Lyc e 3) expression". Plant Biotechnol J 4 (2): 231-42. PMID 17177799.
^ Gavilano L, Coleman N, Burnley L, Bowman M, Kalengamaliro N, Hayes A, Bush L, Siminszky B (2006). "Genetic engineering of Nicotiana tabacum for reduced nornicotine content". J Agric Food Chem 54 (24): 9071–8. PMID 17117792.
^ Allen R, Millgate A, Chitty J, Thisleton J, Miller J, Fist A, Gerlach W, Larkin P (2004). "RNAi-mediated replacement of morphine with the nonnarcotic alkaloid reticuline in opium poppy". Nat Biotechnol 22 (12): 1559–66. PMID 15543134.
^ Zadeh A, Foster G (2004). "Transgenic resistance to tobacco ringspot virus". Acta Virol 48 (3): 145-52. PMID 15595207.
^ Niggeweg R, Michael A, Martin C (2004). "Engineering plants with increased levels of the antioxidant chlorogenic acid". Nat Biotechnol 22 (6): 746-54. PMID 15107863.
^ Sanders R, Hiatt W (2005). "Tomato transgene structure and silencing". Nat Biotechnol 23 (3): 287-9. PMID 15765076.
^ Chiang C, Wang J, Jan F, Yeh S, Gonsalves D (2001). "Comparative reactions of recombinant papaya ringspot viruses with chimeric coat protein (CP) genes and wild-type viruses on CP-transgenic papaya". J Gen Virol 82 (Pt 11): 2827–36. PMID 11602796.
^ Matzke MA, Matzke AJM. (2004). "Planting the Seeds of a New Paradigm.". PLoS Biol 2 (5): e133. PMID 15138502.
^ Ecker JR, Davis RW (1986). "Inhibition of gene expression in plant cells by expression of antisense RNA". Proc Natl Acad Sci U S A 83 (15): 5372–5376. PMID 16593734.
^ Napoli C, Lemieux C, Jorgensen R (1990). "Introduction of a Chimeric Chalcone Synthase Gene into Petunia Results in Reversible Co-Suppression of Homologous Genes in trans". Plant Cell 2 (4): 279–289. PMID 12354959.
^ Romano N, Macino G (1992). "Quelling: transient inactivation of gene expression in Neurospora crassa by transformation with homologous sequences". Mol Microbiol 6 (22): 3343–53. PMID 1484489.
^ Van Blokland R, Van der Geest N, Mol JNM, Kooter JM (1994). "Transgene-mediated suppression of chalcone synthase expression in Petunia hybrida results from an increase in RNA turnover". Plant J 6: 861–77.
^ Covey S, Al-Kaff N, Lángara A, Turner D (1997). "Plants combat infection by gene silencing". Nature 385: 781–2.
^ Ratcliff F, Harrison B, Baulcombe D (1997). "A Similarity Between Viral Defense and Gene Silencing in Plants". Science 276: 1558–60.
^ Guo S, Kemphues K (1995). "par-1, a gene required for establishing polarity in C. elegans embryos, encodes a putative Ser/Thr kinase that is asymmetrically distributed". Cell 81 (4): 611-20. PMID 7758115.
^ Pal-Bhadra M, Bhadra U, Birchler J (1997). "Cosuppression in Drosophila: gene silencing of Alcohol dehydrogenase by white-Adh transgenes is Polycomb dependent". Cell 90 (3): 479-90. PMID 9267028.

Categories: RNA | RNA Interference | Gene expression | Molecular genetics

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "RNA_interference". A list of authors is available in Wikipedia.