RNA functional modulation by Mitoxantrone via RNA structural ensemble repartitioning.

Zhang, Chundan; Borovská, Ivana; Iobashvili, Teona; Morandi, Edoardo; Lionnez, Marta; Olayinka, Oluwatosin S; de Boer, Rinse; Clamer, Massimiliano et al. · Nat Commun · 2026

basic_science · Level V

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Abstract

Targeting RNA with small molecules offers a strategy to modulate gene expression at undruggable targets. Traditional screens favor thermodynamically stable, low-entropy RNA motifs with defined conformations, yet these provide limited energetic leverage for functional modulation. Many RNAs instead sample dynamic structural ensembles that small molecules can repartition. Using group I self-splicing introns as a model, we identified the antineoplastic drug Mitoxantrone as a competitive inhibitor of RNA self-splicing (IC<sub>50</sub> = 4.3 μM) that stabilizes the native conformation of the T4 td intron. Structure-activity analysis showed that the anthraquinone scaffold alone is insufficient, and basic amine-containing side chains are required for RNA structural modulation. Transcriptome-wide chemical probing in human cells revealed preferential binding to GC-rich structured regions, although only a subset showed structural change. Furthermore, global analysis of 5' UTR ensembles showed altered structural heterogeneity and translation, demonstrating functional repartitioning of RNA conformational landscapes.