HNRNPH1 regulates the neuroprotective cold‐shock protein RBM3 expression through poison exon exclusion.

Enhanced expression of the cold‐shock protein RNA binding motif 3 (RBM3) is highly neuroprotective both in vitro and in vivo. Whilst upstream signalling pathways leading to RBM3 expression have been described, the precise molecular mechanism of RBM3 cold induction remains elusive. To identify temperature‐dependent modulators of RBM3, we performed a genome‐wide CRISPR‐Cas9 knockout screen using RBM3‐reporter human iPSC‐derived neurons. We found that RBM3 mRNA and protein levels are robustly regulated by several splicing factors, with heterogeneous nuclear ribonucleoprotein H1 (HNRNPH1) being the strongest positive regulator. Splicing analysis revealed that moderate hypothermia significantly represses the inclusion of a poison exon, which, when retained, targets the mRNA for nonsense‐mediated decay. Importantly, we show that HNRNPH1 mediates this cold‐dependent exon skipping via its thermosensitive interaction with a G‐rich motif within the poison exon. Our study provides novel mechanistic insights into the regulation of RBM3 and provides further targets for neuroprotective therapeutic strategies. Synopsis: RBM3 expression is controlled by temperature‐regulated alternative splicing of a poison exon. The splicing factor HNRNPH1 interacts with G‐rich motifs in RBM3 poison exon in a cooling‐dependent manner to repress poison exon inclusion, increasing RBM3. RBM3 poison exon is preferentially excluded during hypothermia, resulting in reduced NMD‐mediated mRNA degradation and elevated expression.Splicing factor HNRNPH1 regulates RBM3 expression by repressing poison exon inclusion.HNRNPH1 interacts with G‐rich motifs in RBM3 poison exon and this interaction is enhanced at lower temperatures. [ABSTRACT FROM AUTHOR]