Sekioka, R. | Search bioRxiv

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↗

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↗