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Concept: Small interfering RNA


Put a cap on it: Hairpin-shaped RNAs and dumbbell-shaped RNAs were prepared using a thiol-maleimino Michael addition and exhibited good serum and thermal stability. These capped structures were shown to be cleaved by Dicer and RNA interference (RNAi) experiments showed that RhpRNA was highly efficient at RNAi with an IC50 value of 6 pM.

Concepts: Virus, RNA, Small interfering RNA, RNA interference, RNA polymerase, Transposon, RNA-dependent RNA polymerase, RNA-induced transcriptional silencing


Plant parasitic nematodes cause approximately 157 billion US dollars in losses worldwide annually. The soybean cyst nematode (SCN), Heterodera glycines, is responsible for an estimated one billion dollars in losses to the US farmer each year. A promising new approach for control of plant parasitic nematode control is gene silencing. We tested this approach by silencing the SCN gene HgALD, encoding fructose-1,6-diphosphate aldolase. This enzyme is important in the conversion of glucose into energy and may be especially important in actin-based motility during parasite invasion of its host. An RNAi construct targeted to silence HgALD was transformed into soybean roots of composite plants to examine its efficacy to reduce the development of females formed by SCN. The number of mature females on roots transformed with the RNAi construct designed to silence the HgALD gene was reduced by 58%. These results indicate that silencing the aldolase gene of SCN can greatly decrease the number of female SCN reaching maturity, and it is a promising step towards broadening resistance of plants against plant-parasitic nematodes.

Concepts: Bacteria, RNA, Nematode, Small interfering RNA, RNA interference, Gene silencing, Post-transcriptional gene silencing, Heterodera


Non-coding RNAs, especially small RNAs, play important roles in many biological processes. Several small RNA types, including microRNAs (miRNAs) and small interfering RNAs (siRNAs), are well-described in rice (Oryza sativa), although much remains to be learned about their function. Many small RNAs along with their targets have been characterized with deep sequencing technologies. Some special classes of these small RNAs have been found to be unique to rice or within the larger group of grasses. The functional and biological roles of numerous plants small RNAs have been described in detail, including functions as varied as the regulation of tissue development, phase transition, or abiotic and biotic stress resistance. Mutant analysis has proven useful in the genetic identification of components involved in small RNA biogenesis and also in identification of regulatory functions of small RNAs. Although many small RNAs have been identified by deep sequencing in rice, their precise regulatory functions and cell-type specificity are in many cases still unknown.

Concepts: DNA, Gene, RNA, Small interfering RNA, Non-coding RNA, Transfer RNA, Long noncoding RNA, Xist


Human endothelial cells are initiators and targets of the rejection response. Pre-operative modification of endothelial cells by small interfering RNA transfection could shape the nature of the host response post-transplantation. Ablation of endothelial cell class II major histocompatibility complex molecules by small interfering RNA targeting of class II transactivator can reduce the capacity of human endothelial cells to recruit and activate alloreactive T cells. Here, we report the development of small interfering RNA-releasing poly(amine-co-ester) nanoparticles, distinguished by their high content of a hydrophobic lactone. We show that a single transfection of small interfering RNA targeting class II transactivator attenuates major histocompatibility complex class II expression on endothelial cells for at least 4 to 6 weeks after transplantation into immunodeficient mouse hosts. Furthermore, silencing of major histocompatibility complex class II reduces allogeneic T-cell responses in vitro and in vivo. These data suggest that poly(amine-co-ester) nanoparticles, potentially administered during ex vivo normothermic machine perfusion of human organs, could be used to modify endothelial cells with a sustained effect after transplantation.The use of gene silencing techniques in the treatment of post-transplantation host rejection is not long lasting and can have systemic effects. Here, the authors utilize a nanocarrier for siRNA for treatment of arteries ex vivo prior to implantation subsequently attenuating immune reaction in vivo.

Concepts: Immune system, DNA, Gene expression, RNA, Blood vessel, Small interfering RNA, Major histocompatibility complex, In vitro


The therapeutic application of small interfering RNA (siRNA) requires safe nanocarriers for specific and efficient delivery in vivo. Herein, PEGylated cationic cerasomes (PCCs) were fabricated by doping a cationic lipid with hydroxyl group into nanohybrid cerasomes. Multiple properties of PCCs provide a solution to many of the limitations associated with current delivery platforms of siRNA. The polyorganosiloxane surface imparts PCCs higher morphological stability than conventional liposomes. The PEGylation of the cationic cerasome could protect the cerasome nanoparticles from agglomeration and macrophage capture, reduce protein absorption, consequently prolong the blood circulating time and enhance the siRNA delivery efficiency. In addition, incorporation of the lipid containing hydroxyl group further facilitates endosome release. Moreover, PCCs were further to transport siRNA into the cytosol primarily via endocytosis. When applied to systemic administration, PCCs have demonstrated effective delivery into liver and preferential uptake by hepatocytes in mice, thereby leading to high siRNA gene-silencing activity. All these results show potential therapeutic applications of PCCs mediated delivery of siRNA for liver diseases.

Concepts: Protein, RNA, Messenger RNA, Small interfering RNA, RNA interference, Liver, Bile, Proteomics


RNAi is a powerful tool for gene silencing that can be used to reduce undesirable overexpression of oncogenes as a novel form of cancer treatment. However, when using RNAi as a therapeutic tool there is potential for associated gene effects. This study aimed to utilize gold nanoparticles to deliver siRNA into HeLa cells.

Concepts: DNA, Protein, Gene, Gene expression, RNA, Small interfering RNA, RNA interference, Gene silencing


The aim of this study is to establish the safe and effective ocular delivery system of therapeutic small interfering RNA (siRNA) in corneal neovascularization therapy. The major hurdle present in siRNA-based corneal neovascularization (CNV) therapy is severe cytotoxicity caused by repetitive drug treatment. A reducible branched polyethylenimine (rBPEI)-based nanoparticle (NP) system is utilized as a new siRNA carrier as a hope for CNV therapy. The thiolated BPEI is readily self-crosslinked in mild conditions to make high molecular weight rBPEI thus allowing the creation of stable siRNA/rBPEI nanoparticles (siRNA-rBPEI-NPs). In the therapeutic region, the rBPEI polymeric matrix is effectively degraded into nontoxic LMW BPEI inside the reductive cytosol causing the rapid release of the encapsulated siRNA into the cytosol to carry out its function. The fluorescent-labeled siRNA-rBPEI-NPs can release siRNA into the entire corneal region after subconjuctival injection into the eye of Sprague Dawley rats thus confirming the proof of concept of this system.

Concepts: Medicine, RNA, Messenger RNA, Small interfering RNA, RNA interference, Sol-gel, Eye, Laboratory rat


Short interfering RNAs (siRNAs) are promising therapeutics that make use of the RNA interference (RNAi) pathway but liabilities arising from the native RNA structure necessitate chemical modification for drug development. Advances in the structural characterization of components of the human RNAi pathway have enabled structure-guided optimization of siRNA proper-ties. Here we report the 2.3 Å resolution crystal structure of human Argonaute 2 (hAgo2), a key nuclease in the RNAi path-way, bound to a siRNA guide strand bearing an unnatural tria-zolyl nucleotide at position one (g1). Unlike natural nucleo-tides, this analog inserts deeply into hAgo2’s central RNA bind-ing cleft, and is thus able to modulate pairing between guide and target RNAs. The affinity of the hAgo2-siRNA complex for a seed-only matched target was significantly reduced by the tria-zolyl modification while affinity for a fully matched target was unchanged. In addition, siRNA potency for off-target repression was reduced (4-fold increase in IC50) by the modification while on-target knockdown was improved (2-fold reduction in IC50). Controlling siRNA on-target vs miRNA-like off-target potency by projection of substituent groups into the hAgo2 central cleft from g1 is a new approach to enhancing siRNA selectivity with a strong structural rationale.

Concepts: Virus, RNA, Small interfering RNA, RNA interference, RNA polymerase, Transposon, RNA-dependent RNA polymerase, RNA-induced transcriptional silencing


siRNA has been widely applied in research and drug development due to its sequence-specific gene silencing ability. However, how to spatiotemporally control its function is still one of its challenges. Light, a fast and noninvasive trigger, is a promising tool for spatiotemporal control of gene expression. Here, we designed and synthesized a new series of caged siRNAs modified with single cholesterol at 5' terminal of antisense strand RNA through a photolabile linker (Chol-PL-siRNAs). We demonstrated that these caged siRNAs were successfully used to photochemically regulate both exogenous (firefly luciferase and gfp) and endogenous gene expression (mitotic kinesin-5, Eg5) in cells.

Concepts: DNA, Gene, Genetics, Cell nucleus, Gene expression, Molecular biology, RNA, Small interfering RNA


Despite more than two decades of research and development on nucleic acid vaccines, there is still no commercial product for human use. Taking advantage of the recent innovations in systemic delivery of short interfering RNA (siRNA) using lipid nanoparticles (LNPs), we developed a self-amplifying RNA vaccine. Here we show that nonviral delivery of a 9-kb self-amplifying RNA encapsulated within an LNP substantially increased immunogenicity compared with delivery of unformulated RNA. This unique vaccine technology was found to elicit broad, potent, and protective immune responses, that were comparable to a viral delivery technology, but without the inherent limitations of viral vectors. Given the many positive attributes of nucleic acid vaccines, our results suggest that a comprehensive evaluation of nonviral technologies to deliver self-amplifying RNA vaccines is warranted.

Concepts: Immune system, RNA, Vaccine, Vaccination, Immunology, Small interfering RNA, RNA interference, Nucleic acid