Identification of HuR-RNA Interfering Compounds by Dynamic Combinatorial Chemistry and Fluorescence Polarization

Readers of RNA Modification in Cancer and Their Anticancer Inhibitors

Cancer treatment has always been a challenge for humanity. The inadequacies of current technologies underscore the limitations of our efforts against this disease. Nevertheless, the advent of targeted therapy has introduced a promising avenue, furnishing us with more efficacious tools. Consequently, researchers have turned their attention toward epigenetics, offering a novel perspective in this realm. The investigation of epigenetics has brought RNA readers to the forefront, as they play pivotal roles in recognizing and regulating RNA functions. Recently, the development of inhibitors targeting these RNA readers has emerged as a focal point in research and holds promise for further strides in targeted therapy. In this review, we comprehensively summarize various types of inhibitors targeting RNA readers, including non-coding RNA (ncRNA) inhibitors, small-molecule inhibitors, and other potential inhibitors. We systematically elucidate their mechanisms in suppressing cancer progression by inhibiting readers, aiming to present inhibitors of readers at the current stage and provide more insights into the development of anticancer drugs.

Ternary Complex-Templated Dynamic Combinatorial Chemistry for the Selection and Identification of Homo-PROTACs

Dynamic combinatorial chemistry (DCC) leverages a reversible reaction to generate compound libraries from constituting building blocks under thermodynamic control. The position of this equilibrium can be biased by addition of a target macromolecule towards enrichment of bound ligands. While DCC has been applied to select ligands for a single target protein, its application to identifying chimeric molecules inducing proximity between two proteins is unprecedented. In this proof-of-concept study, we develop a DCC approach to select bifunctional proteolysis targeting chimeras (PROTACs) based on their ability to stabilize the ternary complex. We focus on VHL-targeting Homo-PROTACs as model system, and show that the formation of a VHL2 : Homo-PROTAC ternary complex reversibly assembled using thiol-disulfide exchange chemistry leads to amplification of potent VHL Homo-PROTACs with degradation activities which correlated well with their biophysical ability to dimerize VHL. Ternary complex templated dynamic combinatorial libraries allowed identification of novel Homo-PROTAC degraders. We anticipate future applications of ternary-complex directed DCC to early PROTAC screenings and expansion to other proximity-inducing modalities beyond PROTACs.

Assessing the Binding Mode of a Splicing Modulator Stimulating Pre-mRNA Binding to the Plastic U2AF2 Splicing Factor

RNA recognition motifs (RRMs) play a pivotal role in RNA metabolism and the regulation of gene expression. Owing to their plasticity and fuzziness, targeting RRM/RNA interfaces with small molecules is a daunting challenge for drug discovery campaigns. The U2AF2 splicing factor, which recognizes the polypyrimidine (polyPy) sequence of premature messenger (pre-m)RNA, exhibits a dynamic architecture consisting of two RRMs joined by a disordered linker. An inhibitor, NSC-194308, was shown to enhance the binding of pre-mRNA to U2AF2, selectively triggering cell death in leukemia cell lines containing spliceosome mutations. The NSC-194308 binding mode remains elusive; yet, unraveling its knowledge may offer intriguing insights for effectively targeting U2AF2 and other flexible protein/protein/RNA interfaces with small molecules. To infer plausible NSC-194308 binding poses to U2AF2, here, we applied and benchmarked the performance of static and dynamic docking approaches, elucidating the molecular basis of the NSC-194308-induced pre-mRNA stabilization on U2AF2. We demonstrate that introducing dynamic effects is mandatory to assess the binding mode of the inhibitors when they target plastic and modular architectures, such as those formed by interacting RRMs. The latter are widespread across RNA binding proteins; therefore, this mechanism may be broadly applicable to discover new therapeutics aimed at selectively modulating the RNA function by targeting protein/protein/RNA interfaces.