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bioRxiv · 10.1101/2025.10.15.682667

Human Dicer1 hotspot mutation induces both loss and gain of miRNA function

Jee, D.·Lee, S.·Yang, D.·Rickert, R.·Shang, R.·Huangfu, D.·Lai, E. C.
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Abstract

The core miRNA biogenesis enzyme Dicer1 sustains recurrent mutations in cancer that compromise its RNase IIIb domain, which cleaves 5p arms of pre-miRNA hairpins. However, the lack of knockin models has limited fuller understanding. Here, we generated Dicer1-KO and Dicer1-S1344L (homozygous and hemizygous) human ESCs; the latter is a non-catalytic mutation in RNase IIIa that impairs RNase IIIb activity. Dicer1 knockouts lack canonical miRNAs, while S1344L induces two trends: ablation of miRNA-5p strands, and selective changes in miRNA-3p strands. Curiously, we recognized directional upregulation of miRNA-3p passenger strands, indicating a broad strand switch. We used multiple in vitro assays to show 3p arm-nicked pre-miRNAs preferentially load miRNA-3p species into Argonaute, compared to corresponding duplexes. Moreover, activity assays, RNA-seq data, and Argonaute-mRNA profiling, confirm that these confer increased repression capacity. These data expand the molecular consequences of Dicer1 hotspot mutations in cancer.

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Jee, D., Lee, S., Yang, D., Rickert, R., Shang, R., Huangfu, D., Lai, E. C.. 2025-10-15. Human Dicer1 hotspot mutation induces both loss and gain of miRNA function. https://doi.org/10.1101/2025.10.15.682667

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