No abstract

Spherical nucleic acids (SNAs) are nanostructures formed by chemically conjugating short linear strands of oligonucleotides to a nanoparticle template. When made with modified small interfering RNA (siRNA) duplexes, SNAs act as single-entity transfection and gene silencing agents and have been used as lead therapeutic constructs in several disease models. However, the manner in which modified siRNA duplex strands that comprise the SNA lead to gene silencing is not understood. Herein, a systematic analysis of siRNA biochemistry involving SNAs shows that Dicer cleaves the modified siRNA duplex from the surface of the nanoparticle, and the liberated siRNA subsequently functions in a way that is dependent on the canonical RNA interference mechanism. By leveraging this understanding, a class of SNAs was chemically designed which increases the siRNA content by an order of magnitude through covalent attachment of each strand of the duplex. As a consequence of increased nucleic acid content, this nanostructure architecture exhibits less cell cytotoxicity than conventional SNAs without a decrease in siRNA activity.

BACKGROUND Insecticide targets are often identified by mutations that confer resistance, but the intricacies of insecticide binding and downstream processes leading to insect death often remain obscure. Mutations in α6‐like nicotinic acetylcholine receptor subunit genes have been associated with high levels of resistance to spinosad in many insect species, including Drosophila melanogaster. Here, we aimed to expand our understanding of the effects of the natural product insecticide spinosad on its protein target, the α6 subunit, using genetic tools available in D. melanogaster. RESULTS Functional, fluorescently tagged Dα6 subunits (Dα6YFP) were developed to allow observation of the protein in vivo. Larvae expressing Dα6YFP were exposed to a sub‐lethal concentration of spinosyn A (0.025 ppm) for 6 days, leading to a 64% reduction in fluorescence relative to unexposed larvae. Direct application of high doses of spinosyn A to dissected larval brains resulted in a visible 38.25% decrease in Dα6YFP within 20 min, indicating that degradation of the Dα6 protein occurred in response to spinosyn A exposure. Chemical inhibition of the proteasome system using the multiple myeloma treatment drug, PS‐341 reduced loss of Dα6YFP in response to spinosyn A at the 20‐min time point to 6.35%. In addition, in vivo administration of PS‐341 prior to spinosad exposure reduced the effect of spinosad on larval activity. CONCLUSION Based on these data, we propose that exposure to spinosad leads to degradation of the α6‐like target protein, a potentially novel element in the mode of action of spinosyns that may contribute to their toxicity towards insects. © 2021 Society of Chemical Industry

The combination of a boron Lewis acid and a decamethylsamarocene, specifically 9,10-Me2-9,10-diboraanthracene with (C5Me5)2SmII(THF)2, in toluene leads to cooperative reductive capture of N2. The product crystallizes as the salt, [(C5Me5)2SmIII(THF)2][(C5Me5)2SmIII(η2-N2B2C14H14)],...

Katanin microtubule severing enzymes are potent M-phase regulators in oocytes and somatic cells. How the complex, and evolutionarily critical, male mammalian meiotic spindle is sculpted remains unknown. Here, using multiple single and double gene knockout mice, we reveal that the canonical katanin A-subunit, KATNA1, and its close paralogue, KATNAL1, together execute multiple aspects of meiosis. We show KATNA1 and KATNAL1 collectively regulate the male meiotic spindle, cytokinesis and midbody abscission, in addition to diverse spermatid remodelling events, including Golgi organisation, and acrosome and manchette formation. We also define KATNAL1-specific roles in sperm flagella development, manchette regulation, and sperm-epithelial disengagement. Finally, using proteomic approaches we define the KATNA1, KATNAL1, and KATNB1 mammalian testis interactome, which includes a network of cytoskeletal and vesicle trafficking proteins. Collectively, we reveal the presence of multiple katanin A-subunit paralogs in mammalian spermatogenesis allows for ′customized cutting′ via neofunctionalization and protective buffering via gene redundancy.