Targeted degradation via direct 26S proteasome recruitment.

Engineered destruction of target proteins by recruitment to the cell's degradation machinery has emerged as a promising strategy in drug discovery. The majority of molecules that facilitate targeted degradation do so via a select number of ubiquitin ligases, restricting this therapeutic approach to tissue types that express the requisite ligase. Here, we describe a new strategy of targeted protein degradation through direct substrate recruitment to the 26S proteasome. The proteolytic complex is essential and abundantly expressed in all cells; however, proteasomal ligands remain scarce. We identify potent peptidic macrocycles that bind directly to the 26S proteasome subunit PSMD2, with a 2.5-Å-resolution cryo-electron microscopy complex structure revealing a binding site near the 26S pore. Conjugation of this macrocycle to a potent BRD4 ligand enabled generation of chimeric molecules that effectively degrade BRD4 in cells, thus demonstrating that degradation via direct proteasomal recruitment is a viable strategy for targeted protein degradation.

Potency-Enhanced Peptidomimetic VHL Ligands with Improved Oral Bioavailability.

The von Hippel-Lindau (VHL) protein plays a pivotal role in regulating the hypoxic stress response and has been extensively studied and utilized in the targeted protein degradation field, particularly in the context of bivalent degraders. In this study, we present a comprehensive peptidomimetic structure-activity relationship (SAR) approach, combined with cellular NanoBRET target engagement assays to enhance the existing VHL ligands. Through systematic modifications of the molecule, we identified the 1,2,3-triazole group as an optimal substitute of the left-hand side amide bond that yields 10-fold higher binding activity. Moreover, incorporating conformationally constrained alterations on the methylthiazole benzylamine moiety led to the development of highly potent VHL ligands with picomolar binding affinity and significantly improved oral bioavailability. We anticipate that our optimized VHL ligand, GNE7599, will serve as a valuable tool compound for investigating the VHL pathway and advancing the field of targeted protein degradation.

Functional significance of U2AF1 S34F mutations in lung adenocarcinomas.

The functional role of U2AF1 mutations in lung adenocarcinomas (LUADs) remains incompletely understood. Here, we report a significant co-occurrence of U2AF1 S34F mutations with ROS1 translocations in LUADs. To characterize this interaction, we profiled effects of S34F on the transcriptome-wide distribution of RNA binding and alternative splicing in cells harboring the ROS1 translocation. Compared to its wild-type counterpart, U2AF1 S34F preferentially binds and modulates splicing of introns containing CAG trinucleotides at their 3' splice junctions. The presence of S34F caused a shift in cross-linking at 3' splice sites, which was significantly associated with alternative splicing of skipped exons. U2AF1 S34F induced expression of genes involved in the epithelial-mesenchymal transition (EMT) and increased tumor cell invasion. Finally, S34F increased splicing of the long over the short SLC34A2-ROS1 isoform, which was also associated with enhanced invasiveness. Taken together, our results suggest a mechanistic interaction between mutant U2AF1 and ROS1 in LUAD.

Hitting a Moving Target: A Strategic Tool for Analyzing Terrorist Threats.

The subject of terrorism risk can be confusing for both the general public and for those responsible for protecting us from attack. Relatively minor terrorist threats are often conflated with much more serious ones, in part because it is hard to quantify either intent or technical ability to carry out an attack. Plotting threats on a "potential mass casualties" versus "ease of obtainment or production" matrix creates some order out of a seemingly endless array of worldwide threats, and it highlights those threats that are in need of more urgent attention. The specific threats on this 2x2 matrix can fall into one or multiple quadrants, which can be qualitatively described as "most dangerous," "dangerous but difficult," "worrisome," and "persistent terror." By placing threats into these quadrants and illustrating movement within and between them, the matrix can help (1) visualize and parse a diverse set of threats, (2) view how threats have changed over time and judge the efficacy of current countermeasures, and (3) evaluate the merit of future actions and investments. Having a dynamic matrix that can visually map the comparative risk of terrorist threat events in toto and that can help us monitor the effectiveness of present and future resource investments can add intellectual rigor to some of the most difficult and daunting decisions pertaining to our nation's safety and security.