Biology subjects

Disney, M. D.

Publications and source records attributed to Disney, M. D..

At least 19 recordsLinked to original sources

bioRxiv2026

A Minimal Synthetic Cleavage Module Enables Selective Degradation of Pathogenic r(CUG) Repeats in Cells

Although direct RNA degradation offers an alternative to occupancy-driven activity, it has relied on complex natural product-derived cleavage modules such as bleomycin. Here, we show that a compact synthetic Fe(II)-coordinating warhead can be programmed for selective RNA degradation in cells. Coupling this cleavage module to a small molecule that recognizes expanded r(CUG) repeats that cause myotonic dystrophy type 1 (DM1) afforded selective degradation of the pathogenic RNA while sparing wild type and transcripts harboring short r(CUG) repeats. In DM1 patient-derived myoblasts, degradation of mutant repeat RNA reduced DM1-associated pathology including formation of nuclear foci, sequestration of MBNL1, and alternative pre-mRNA splicing defects, without inducing DNA damage. These studies establish that minimal synthetic cleavage modules can replace complex natural product warheads to enable selective degradation of disease-causing RNAs in cells.

biochemistry↗

bioRxiv2026

SMARTFlexDB: a paired apo-holo RNA structure database and analysis platform for RNA conformational flexibility and small-molecule recognition

RNA structures can undergo substantial conformational changes upon small-molecule binding, yet existing structural resources provide only static RNA-ligand snapshots without connecting ligand-bound (holo) RNA structures to corresponding ligand-free (apo) conformations. SMARTFlexDB is a curated database and analysis platform that uses paired apo-holo RNA structures to characterize conformational differences and RNA-small-molecule recognition. Candidate pairs were identified from the Protein Data Bank by matching RNA chains with at least 90% sequence identity and coverage, and fully conserved binding pocket nucleotides. The current release contains 434 binding pockets from 266 holo structures, linked to 186 apo structures to yield 1,187 pocket-level apo-holo pairs organized into 734 database entries, spanning 150 small molecules and 23 RNA functional classes. Each entry integrates RNA sequence and secondary-structure annotations, apo and holo three-dimensional structures, RNA-ligand atomic interactions, and quantitative descriptors of global and local conformational changes. An interactive web interface enables users to explore sequence alignments and structural overlays, compare secondary structures and RNA motifs, and upload paired apo-holo structures for customized analysis. By linking ligand-bound and ligand-free RNA structures, SMARTFlexDB provides a robust foundation for investigating RNA structural flexibility and supporting RNA-targeted small-molecule drug discovery. The database and analysis platform are available at https://aidd.rc.ufl.edu/app/smartflexdb/.

bioinformatics↗

bioRxiv2026

Programmable Recruitment of RNA-Binding Proteins Enables Small Molecule-Directed Destabilization of Nuclear Pre-mRNA

Chemically induced proximity has not been systematically applied to control RNA fate. Here, a programmable platform was developed to identify RNA-binding proteins (RBPs) that can be recruited by small molecules to destabilize RNA. Using microtubule-associated protein Tau (MAPT) pre-mRNA as a model target, a heterobifunctional molecule was designed to bind both a ligandable structure in MAPT pre-mRNA and FKBP12F36V-tagged RBPs. Screening of a library of tagged RBPs identified several proteins that reduced MAPT RNA levels, including zinc finger protein 36 (ZFP36) and nanos C2HC-type zinc finger 3 (NANOS3). The approach was then extended from engineered proteins to an endogenous RBP. Using small molecule ligandability maps, a cysteine-reactive ligand for ZFP36 was identified. When this ligand was linked to the MAPT-binding small molecule, endogenous ZFP36 was recruited to MAPT mRNA, reducing its abundance in cells. Genetic and chemical controls demonstrated that activity was dependent on both RNA binding and ZFP36 recruitment, supporting an induced-proximity mechanism. These studies establish a general strategy for identifying new recruitable RBP effectors and should advance ribonuclease-targeting chimera (RiboTAC) technology by expanding the repertoire of effector proteins that can be harnessed for RNA degradation. More broadly, new effectors can be discovered through model reporter-based screens and translated to endogenous systems by mining known protein binders and ligandability maps, providing a systematic path to develop small molecules that control RNA stability, including RNAs targeted through structured regions of nuclear pre-mRNAs.

biochemistry↗

bioRxiv2026

Geometric Deep Learning Reveals Ligandable and Cryptic RNA Binding Small Molecule Pockets (SMARTPocket)

RNAs are important therapeutic targets, however identifying ligandable small-molecule binding pockets remains a major barrier to RNA-targeted drug discovery. Here, SMARTPocket, an atomic-level geometric deep learning framework for predicting RNA-small molecule binding pockets directly from three-dimensional structure is introduced. SMARTPocket represents RNA as full-atom point clouds and uses transfer learning from more than 110,000 protein binding interface structures to overcome the limited number of experimentally elucidated RNA-ligand complexes. Across four established single-chain benchmarks and three broader curated benchmarks, SMARTPocket consistently outperforms existing RNA pocket predictors and general biomolecular modeling approaches. The model generalizes to apo RNA structures when conformational changes are modest, identifies cryptic ligandable pockets, and recapitulates experimentally validated binding sites in the SARS-CoV-2 frameshifting element and an RNA aptamer evolved to bind small molecules. SMARTPocket-guided docking further improves near-native RNA-ligand pose recovery and computational efficiency compared with blind docking. These results establish SMARTPocket as a generalizable framework for structure-based identification of ligandable RNA pockets and for accelerating discovery of RNA-targeted small molecules.

bioinformatics↗

bioRxiv2026

A chemoinformatics-guided platform for efficient discovery of RNA-binding small molecules: Proof-of-concept for myotonic dystrophy type 1

Structured RNAs cause human diseases but remain challenging to target selectively with small molecules. Here, we report a chemoinformatics-guided discovery framework that integrates fingerprint-based molecular design, experimental validation, and mechanistic profiling to identify small molecules that bind highly structured, disease-associated RNAs. Using an RNA-binder fingerprint derived from known ligands, a Tversky similarity screen of >8 million compounds yielded a 150-member library enriched in chemical space for RNA-active scaffolds. Target engagement and cell-based assays identified multiple selective ligands for the pathogenic expanded triplet repeat, r(CUG)exp, that causes myotonic dystrophy type 1 (DM1) by binding and sequestering the RNA-binding protein muscleblind-like 1 (MBNL1). Biophysical and single-molecule analyses revealed that the small molecules bind the 1x1 nucleotide U/U internal loops formed when r(CUG)exp folds, partially block MBNL1 binding, and modulate RNA folding equilibria. Two optimized scaffolds rescued MBNL1-dependent splicing in patient-derived myotubes with micromolar potency and minimal cytotoxicity. This study establishes a generalizable, data-driven platform for discovering drug-like RNA-binding lead small molecules and demonstrates its application to the toxic repeat expansion RNA underlying DM1. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=97 SRC="FIGDIR/small/723748v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@1a87b41org.highwire.dtl.DTLVardef@340a14org.highwire.dtl.DTLVardef@81b583org.highwire.dtl.DTLVardef@1b3ba14_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract C_FIG

bioinformatics↗

bioRxiv2026

Mechanistically Defined Epoxide- and Aziridine-2-carboxamide Electrophiles Enable Stereoselective Covalent RNA Modulation

RNA remains a largely untapped target for covalent small-molecule intervention due to the lack of electrophiles with predictable reactivity and stability in biological settings. Here, a mechanistically defined and tunable class of epoxide- and aziridine-2-carboxamide electrophiles that enable structure-guided covalent targeting of RNA is described. These warheads arise from an unexpected hydrolytic rearrangement of 3-chloropivalamide precursors under physiological conditions and selectively react with guanine N7, with reactivity and stability controlled by substitution pattern, linkage chemistry, and stereochemistry. Application to two distinct RNA targets demonstrates generality: epoxide- and aziridine-based ligands covalently modify pathogenic r(CUG)exp repeat RNA and disrupt RNA-protein interactions in vitro and in cells, while structure-guided placement on a flavin scaffold yields stereoselective covalent modulators of the flavin mononucleotide (FMN) riboswitch with validated reaction site and cellular activity. Together, this work establishes epoxide- and aziridine-2-carboxamides as a versatile platform for covalent RNA targeting and provides a general framework for the rational design of stereochemically controlled RNA-reactive small molecules.

biochemistry↗

bioRxiv2025

Small Molecule Degradation of the microRNA-21 Precursor Rescues Pathogenic Pathways in Cellular Models of Fibrosis

MicroRNAs (miRNAs) are short RNA molecules that bind to target mRNAs, resulting in translational repression and gene silencing. Overexpression of microRNA-21 (miR-21) is associated with various human diseases, including autosomal dominant polycystic kidney disease (ADPKD) and pulmonary fibrosis. In this study, a previously described heterobifunctional molecule, TGP-21-RiboTAC, that degrades the miR-21 precursor (pre-miR-21) in triple negative breast cancer cells was investigated in polycystic kidney cell lines and a lung fibroblast cell line. In the former, TGP-21-RiboTAC degraded pre-miR-21 and de-repressed of miR-21s downstream target, Programmed Cell Death 4 (PDCD4) and Peroxisome Proliferator-Activated Receptor alpha (PPAR), known drivers of ADPKD. The heterobifunctional molecule also inhibited cyst growth and rescued the metabolic alterations that occur in ADPKD. In the lung fibroblast cell line, MRC-5, TGP-21-RiboTAC also reduced pre- and mature miR-21 levels, rescued Transforming Growth Factor {beta} (TGF-{beta})-induced repression of SMAD Family Member 7 (SMAD7) and inhibited cell invasion. Collectively, these studies demonstrate the potential of targeted RNA degradation as therapeutic agents that retard the development of organ fibrosis.

biochemistry↗

bioRxiv2025

RNA-Focused DNA-Encoded Library Construction, Screening, and Integration of Docking Identify Bioactive Ligands of Pathogenic r(G4C2)exp RNA

Disease-associated RNAs are increasingly recognized as promising therapeutic targets for small-molecule intervention. While DNA-encoded libraries (DELs) have long been established for protein ligand discovery, recent studies have demonstrated their feasibility for identifying RNA-binding small molecules. To further advance RNA-targeted ligand discovery, a diverse, solid-phase DEL enriched in privileged RNA-binding scaffolds was constructed and applied to identify ligands of r(G4C2)exp, a toxic RNA repeat expansion implicated in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). DEL selection outcomes were analyzed through large-scale molecular docking integrated with physicochemical and structure-activity relationship (SAR) analyses. Strong correlations were observed between docking predictions and experimental enrichment trends, supporting lead identification. The lead compound was subsequently optimized based on its docked pose to an NMR structure, resulting in analogs with enhanced binding affinity and bioactivity. These findings demonstrate that RNA ligand identification can be effectively achieved by combining DNA-encoded library technology with computational approaches for rational design and analysis, and highlight a broadly adaptable platform for RNA-targeted small molecule discovery. TOC graphic O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=104 SRC="FIGDIR/small/686979v1_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@1c9f24borg.highwire.dtl.DTLVardef@1422413org.highwire.dtl.DTLVardef@14e73a2org.highwire.dtl.DTLVardef@189a0bc_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2025

Live-Cell Covalent Profiling Reveals Principles of RNA-Small Molecule Recognition across the Human Transcriptome

RNA folds are abundant in mammalian cells yet poorly characterized as small-molecule targets. We present a scalable, unbiased live-cell pipeline that maps where small molecules bind RNA across the human transcriptome and convert those binders into selective degraders. A 200-member fragment library bearing diazirine/alkyne handles yielded 23 RNA-binding candidates. Chem-CLIP-Map-Seq in MDA-MB-231 cells identified 723 RNA targets and their binding sites, revealing a strong bias toward 5' and 3' untranslated regions (UTRs) in mRNAs and enrichment at thermodynamically stable structures, with limited binding to non-coding RNAs. Expression level and local stability contributed to engagement. An integrated machine-learning model trained on multiple fingerprints distinguished binders from non-binders, and highlighted chemotypes and physicochemical features that favor RNA recognition. Four fragments were converted to RiboTACs; despite broad binding, cleavage was highly selective, with X1-RiboTAC degrading MPP7 and SSC4D mRNAs in an RNase L-dependent manner and reducing their protein levels. A competitive profiling workflow quantified in-cell target occupancy and guided optimization of the RNA-binding module to reprogram selectivity: an X1 derivative produced an MPP7-selective RiboTAC that lowered MPP7 mRNA levels and suppressed breast-cancer cell migration, while sparing SSC4D transcripts. This end-to-end framework, including transcriptome-wide mapping, data-driven rules, and tunable degradation, establishes practical principles for ligandable RNA sites in cells and enables rational design of RNA-targeted small molecules and degraders. TEASERLive-cell mapping reveals ligandable RNA sites and guides design of selective RNA degraders. TOC graphic O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=61 SRC="FIGDIR/small/686775v1_ufig1.gif" ALT="Figure 1"> View larger version (16K): org.highwire.dtl.DTLVardef@a216c8org.highwire.dtl.DTLVardef@185c59eorg.highwire.dtl.DTLVardef@17131e2org.highwire.dtl.DTLVardef@81ffa2_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2025

Small Molecule Approach to RNA Targeting Binder Discovery (SMARTBind) Using Deep Learning Without Structural Input

Accurate identification of small molecule binders to RNA is critical for chemical probes and therapeutics. Computational approaches offer a cost-effective strategy to identify small molecules targeting RNA but are often limited by poor predictive accuracy and high computational demands. Here, we introduce Small Molecule Approaches to RNA Targeting Binder Discovery (SMARTBind), a structure-agnostic ligand discovery framework that combines an RNA large language model with contrastive learning and a ligand-specific decoy enhancement strategy. The RNA language model, pre-trained on millions of RNA sequences, together with the decoy enhancement strategy, addresses data scarcity and improves model generalizability. SMARTBind uses only RNA primary sequence to identify small molecule binders and their binding sites accurately. Across multiple benchmarks and case studies, SMARTBind outperforms existing data-driven and docking-based methods while significantly reducing computational cost. In a real- world application, SMARTBind identified novel small molecules targeting the precursor of oncogenic microRNA-21, validated by in vitro and cellular assays. These results highlight SMARTBinds potential as a scalable, accurate, and structure-independent platform for RNA-targeted small molecule discovery.

bioinformatics↗

bioRxiv2025

Structure-Guided Design of a Bioactive Covalent Small Molecule Targeting a Riboswitch

Small molecule ligands targeting structured RNA elements hold promise for modulating RNA function, serving as chemical probes and potential therapeutics. In this study, the characterization of phenylglyoxal-based covalent probe designed to target unpaired guanine residues in structured RNAs is reported. A structure-guided design strategy was employed to modify covalently unpaired guanines critical for flavin mononucleotide (FMN) binding to the FMN riboswitch. Covalent modification occurs at the designed site and modulates riboswitch function in a cellular reporter system, highlighting the potential of covalent mechanisms of action for bioactive RNA ligands.

biochemistry↗

bioRxiv2025

Design of an orally bioavailable small molecule that modulates the microtubule-associated protein tau's pre-mRNA splicing

Frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP-17) is caused by the aberrant alternative pre-mRNA splicing of microtubule-associated protein tau (MAPT) exon 10, the inclusion of which encodes for a toxic tau protein harboring four microtube domains (4R tau). Here, we describe the design of an RNA-targeted small molecule that thermodynamically stabilizes the structure of a pre-mRNA splicing regulator element in the MAPT pre-mRNA exon 10-intron junction to reduce the inclusion of exon 10 and hence 4R tau abundance. Structure-based drug design was used to obtain compounds that form a network of specific interactions to the RNA including multiple interactions between a one nucleotide A-bulge and the Hoogsteen face of a closing GC base pair, the latter of which was enabled by the design of base triple interactions. A battery of assays revealed that the compound binds the target in vitro and in cells and affects pre-mRNA splicing in various cellular models including primary neurons from a human tau (htau) knock-in mouse model. The orally bioavailable compound was administered per os (p.o.), where treatment diminished exon 10 inclusion, and reduced the 4R tau protein isoform. Further, the molecule mitigated cellular pathologies and behavioral phenotypes observed in the htau transgenic mouse model. This study provides a potentially general pipeline to design compounds that target RNAs and affect disease pathways and deliver compounds that have oral bioavailability and blood-brain barrier penetrance.

biochemistry↗

bioRxiv2025

Discovery of RNA-Reactive Small Molecules Guides Design of Electrophilic Modules for RNA-Specific Covalent Binders

RNA is a key drug target that can be modulated by small molecules, however covalent binders of RNA remain largely unexplored. Using a high-throughput mass spectrometry screen of 2,000 electrophilic compounds, we identified ligands that react with RNA in a binding-dependent manner. RNA reactivity was influenced by both the reactive group and the RNA-binding scaffold. Electrophilic modules such as 3-chloropivalamide, bis(2-chloroethyl)amine, chloroacetamide, and N-acylimidazole that react with proteins also cross-linked to RNA, especially when paired with aromatic heterocycles, particularly those with a thieno[3,2-c]pyridinium core. These results suggest that electrophiles commonly used for protein targeting can also covalently modify RNA, potentially contributing to both on- and off-target effects. This insight enabled the design of an RNA-specific covalent compound by modifying a Hoechst scaffold, originally identified to bind DNA, to react selectively with the expanded triplet repeat RNA, r(CUG)exp, that causes myotonic dystrophy type 1 (DM1). Selectivity appears to arise from binding to the RNA major groove near the reactive site. Overall, this study highlights the potential of rationally designing covalent RNA-targeting small molecules. TOC Graphic O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=54 SRC="FIGDIR/small/649986v1_ufig1.gif" ALT="Figure 1"> View larger version (12K): org.highwire.dtl.DTLVardef@2049c7org.highwire.dtl.DTLVardef@1cbc49aorg.highwire.dtl.DTLVardef@d88363org.highwire.dtl.DTLVardef@99fef8_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2024

NMR structures and magnetic force spectroscopy studies of small molecules binding to models of an RNA CAG repeat expansion

RNA repeat expansions fold into stable structures and cause microsatellite diseases such as Huntingtons disease (HD), myotonic dystrophy type 1 (DM1), and spinocerebellar ataxias (SCAs). The trinucleotide expansion of r(CAG), or r(CAG)exp, causes both HD and SCA3, and the RNAs toxicity has been traced to its translation into polyglutamine (polyQ; HD) as well as aberrant pre-mRNA alternative splicing (SCA3 and HD). Previously, a small molecule, 1, was discovered that binds to r(CAG)exp and rescues aberrant pre-mRNA splicing in patient-derived fibroblasts by freeing proteins bound to the repeats. Here, we report the structures of single r(CAG) repeat motif (5CAG/3GAC where the underlined adenosines form a 1x1 nucleotide internal loop) in complex with 1 and two other small molecules via nuclear magnetic resonance (NMR) spectroscopy combined with simulated annealing. Compound 2 was designed based on the structure of 1 bound to the RNA while 3 was selected as a diverse chemical scaffold. The three complexes, although adopting different 3D binding pockets upon ligand binding, are stabilized by a combination of stacking interactions with the internal loops closing GC base pairs, hydrogen bonds, and van der Waals interactions. Molecular dynamics (MD) simulations performed with NMR-derived restraints show that the RNA is stretched and bent upon ligand binding with significant changes in propeller-twist and opening. Compound 3 has a distinct mode of binding by insertion into the helix, displacing one of the loop nucleotides into the major groove and affording a rod-like shape binding pocket. In contrast, 1 and 2 are groove binders. A series of single molecule magnetic force spectroscopy studies provide a mechanistic explanation for how bioactive compounds might rescue disease-associated cellular phenotypes. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=87 SRC="FIGDIR/small/608150v1_ufig1.gif" ALT="Figure 1"> View larger version (22K): org.highwire.dtl.DTLVardef@145398org.highwire.dtl.DTLVardef@7c37caorg.highwire.dtl.DTLVardef@132cbbeorg.highwire.dtl.DTLVardef@1de59d3_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2024

NMR structures of small molecules bound to a model of an RNA CUG repeat expansion

Trinucleotide repeat expansions fold into long, stable hairpins and cause a variety of incurable RNA gain-of-function diseases such as Huntingtons disease, the myotonic dystrophies, and spinocerebellar ataxias. One approach for treating these diseases is to bind small molecules to the structured RNAs. Both Huntingtons disease-like 2 (HDL2) and myotonic dystrophy type 1 (DM1) are caused by a r(CUG) repeat expansion, or r(CUG)exp. The RNA folds into a hairpin structure with a periodic array of 1x1 nucleotide UU loops (5CUG/3GUC; where the underlined nucleotides indicate the Us in the internal loop) that sequester various RNA-binding proteins (RBP) and hence the source of its gain-of-function. Here, we report NMR-refined structures of single 5CUG/3GUC motifs in complex with three different small molecules, a diguandinobenzoate (1), a derivative of 1 where the guanidino groups have been exchanged for imidazole (2), and a quinoline with improved drug-like properties (3). These structures were determined using nuclear magnetic resonance (NMR) spectroscopy and simulated annealing with restrained molecular dynamics (MD). Compounds 1, 2, and 3 formed stacking and hydrogen bonding interactions with the 5CUG/3GUC motif. Compound 3 also formed van der Waals interactions with the internal loop. The global structure of each RNA-small molecule complexes retains an A-form conformation, while the internal loops are still dynamic but to a lesser extent compared to the unbound form. These results aid our understanding of ligand-RNA interactions and enable structure-based design of small molecules with improved binding affinity for and biological activity against r(CUG)exp. As the first ever reported structures of RNA r(CUG) repeats bound to ligands, these structures can enable virtual screening campaigns combined with machine learning assisted de novo design.

biochemistry↗

bioRxiv2023

Development of MAPT S305 mutation models exhibiting elevated 4R tau expression, resulting in altered neuronal and astrocytic function

Due to the importance of 4R tau in the pathogenicity of primary tauopathies, it has been challenging to model these diseases in iPSC-derived neurons, which express very low levels of 4R tau. To address this problem we have developed a panel of isogenic iPSC lines carrying the MAPT splice-site mutations S305S, S305I or S305N, derived from four different donors. All three mutations significantly increased the proportion of 4R tau expression in iPSC-neurons and astrocytes, with up to 80% 4R transcripts in S305N neurons from as early as 4 weeks of differentiation. Transcriptomic and functional analyses of S305 mutant neurons revealed shared disruption in glutamate signaling and synaptic maturity, but divergent effects on mitochondrial bioenergetics. In iPSC-astrocytes, S305 mutations induced lysosomal disruption and inflammation and exacerbated internalization of exogenous tau that may be a precursor to the glial pathologies observed in many tauopathies. In conclusion, we present a novel panel of human iPSC lines that express unprecedented levels of 4R tau in neurons and astrocytes. These lines recapitulate previously characterized tauopathy-relevant phenotypes, but also highlight functional differences between the wild type 4R and mutant 4R proteins. We also highlight the functional importance of MAPT expression in astrocytes. These lines will be highly beneficial to tauopathy researchers enabling a more complete understanding of the pathogenic mechanisms underlying 4R tauopathies across different cell types.

neuroscience↗

bioRxiv2020

Small molecules exploiting structural differences within microRNA-200 precursors family members reverse a type 2 diabetes phenotype

MicroRNA families are pervasive in the human transcriptome, but specific targeting of individual members is a challenge because of sequence homology. Many of the secondary structures of the precursors to these miRs (pre-miRs), however, are quite different. Here, we demonstrate both in vitro and in cellulis that design of structure-specific small molecules can inhibit specific miR family members to modulate a disease pathway. In particular, the miR-200 family consists five miRs, miR-200a, −200b, −200c, −141, and - 429, and is associated with Type II Diabetes (T2D). We designed a small molecule that potently and selectively targets pre-miR-200c’s structure. The compound reverses a pro-apoptotic effect in a pancreatic β-cell model. In contrast, oligonucleotides targeting the RNA’s sequence inhibit all family members. Global proteomics analysis further demonstrates selectivity for miR-200c. Collectively, these studies establish that miR-200c plays an important role in T2D and that small molecules targeting RNA structure can be an important complement to oligonucleotides targeting sequence.Significance Statement The most common way to develop medicines targeting RNA is by using oligonucleotides that target its sequence by using base pairing. Some RNAs, however, have similar sequences and thus are impossible to target selectively by using oligonucleotides. Here, we show that a class of RNAs that have similar sequences emerge from precursors that have very different structures. Exploiting these structural differences afforded a selective compound. In particular, the selective small molecule targets a member of the microRNA (miR)-200 family, the overexpression of which is linked to diabetes and pancreatic cell death. Selective inhibition of family member miR-200c alleviates pancreatic cell death, and thus the small molecule provides a path to the treatment of diabetes.Competing Interest StatementMDD is a founder of expansion therapeuticsView Full Text

biochemistry↗

bioRxiv2020

A small molecule that binds an RNA repeat expansion stimulates its decay via the exosome complex

We describe the design of a small molecule that binds the structure of a r(CUG) repeat expansion [r(CUG)exp] and reverses molecular defects in two diseases mediated by the RNA - myotonic dystrophy type 1 (DM1) and Fuchs endothelial corneal dystrophy (FECD). Thus, a single structure-specific ligand has potential therapeutic benefit for multiple diseases, in contrast to oligonucleotide-based modalities that are customized for each disease by nature of targeting the gene that harbors the repeat. Indeed, the small molecule binds the target with nanomolar affinity and >100-fold specificity vs. many other RNAs and DNA. Interestingly, the compounds downstream effects are different in the two diseases, owing to the location of the repeat expansion. In DM1, r(CUG)exp is harbored in the 3 untranslated region (UTR) of and mRNA, and the compound has no effect on the RNAs abundance. In FECD, however, r(CUG)exp is located in an intron, and the small molecule, by binding the repeat expansion, facilitates excision of the intron, which is then degraded by the exosome complex exonuclease, hRRP6. Thus, structure-specific, RNA-targeting small molecules can act disease-specifically to affect biology, either by disabling its gain-of-function mechanism (DM1) or by stimulating quality control pathways to rid a disease-affected cell of a toxic RNA (FECD). Significance statementMany different diseases are caused by toxic structured RNAs. Herein, we designed a lead small molecule that binds a toxic structure and rescues disease biology. We show that a structure-specific small molecule can improve disease-associated defects in two diseases that share the common toxic RNA structure. In one disease, the toxic structure is harbored in an intron and causes its retention. The compound facilitates processing of a retained intron, enabling the disease-affected cell to remove the toxic RNA.

cell biology↗