Highlights d The CBASS-associated nuclease NucC kills phage-infected cells by genome destruction d Binding of a cyclic triadenylate second messenger causes NucC homohexamer assembly d NucC hexamer assembly juxtaposes pairs of active sites to activate DNA cleavage d NucC is found in both CBASS systems and type III CRISPR/ Cas systems

Spider silk is a striking and robust natural material that has an unrivaled combination of strength and elasticity. There are two major problems in creating materials from recombinant spider silk proteins (rSSps): expressing sufficient quantities of the large, highly repetitive proteins and solvating the naturally self-assembling proteins once produced. To address the second problem, we have developed a method to rapidly dissolve rSSps in water in lieu of traditional organic solvents and accomplish nearly 100% solvation and recovery of the protein. Our method involves generating pressure and temperature in a sealed vial by using short, repetitive bursts from a conventional microwave. The method is scalable and has been successful with all rSSps used to date. From these easily generated aqueous solutions of rSSps, a wide variety of materials have been produced. Production of fibers, films, hydrogels, lyogels, sponges, and adhesives and studies of their mechanical and structural properties are reported. To our knowledge, ours is the only method that is cost-effective and scalable for mass production. This solvation method allows a choice of the physical form of product to take advantage of spider silks' mechanical properties without using costly and problematic organic solvents.

Bacteria possess an array of defenses against foreign invaders, including diverse nucleases that target and destroy the genome of an invading bacteriophage or foreign DNA element. A recently-described bacteriophage immunity pathway employs a cGAS/DncV-like nucleotidyltransferase to produce a cyclic tri-AMP second messenger, which activates the DNA endonuclease effector NucC. Here, we show that NucC is related to restriction enzymes but uniquely assembles into a homotrimer in solution. cAAA binding in a conserved allosteric pocket promotes assembly of two NucC trimers into a homohexamer competent for doublestrand DNA cleavage. We propose that NucC mediates bacteriophage immunity either through global activation, causing altruistic cell death and abortive infection, or through local activation and targeted phage genome destruction. Finally, we identify NucC homologs in type III CRISPR-Cas systems, where they likely function as accessory nucleases activated by cyclic oligoadenylate second messengers synthesized by these systems' effector complexes.

Synaptic dysfunction has been implicated as an early cause of cognitive decline in neurodegenerative diseases (NDDs) such as Alzheimer’s disease (AD). Methods to slow down or reverse the loss of functional synapses, therefore, represent a promising avenue to explore for treating NDDs. We have previously reported the development of a class of benzothiazole amphiphiles (BAMs) that exhibited the capability to improve memory and learning both in wild‐type mice and in an AD rodent model, putatively through promoting RasGRF1‐associated formation of dendritic spines in hippocampal neurons. While these results represent a good first step in exploring a new approach to treating NDDs, the capability of these compounds to increase spine density has not been previously examined in a human neuronal model. Here, we found that neurons derived from differentiated human induced pluripotent stem cells exhibited both an increase in RasGRF1 expression and a phenotypic increase in the density of postsynaptic density protein 95‐positive puncta (which we use to provide an estimate of dendritic spine density) in BAM‐treated vs. control neurons. These results demonstrate that the previously observed spinogenic effects of BAMs in rodent neurons can be recapitulated in a human neuronal model, which further supports the potential utility of BAM agents for treating human diseases associated with spine deficits such as AD or other NDDs.

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