School of Biological Sciences, Nanyang Technological University, 637551 Singapore.
Nucleic Acids Res. 2022 Aug 26;50(15):8599-8614. doi: 10.1093/nar/gkac669.
SRRM2 is a nuclear-speckle marker containing multiple disordered domains, whose dysfunction is associated with several human diseases. Using mainly EGFP-SRRM2 knock-in HEK293T cells, we show that SRRM2 forms biomolecular condensates satisfying most hallmarks of liquid-liquid phase separation, including spherical shape, dynamic rearrangement, coalescence and concentration dependence supported by in vitro experiments. Live-cell imaging shows that SRRM2 organizes nuclear speckles along the cell cycle. As bona-fide splicing factor present in spliceosome structures, SRRM2 deficiency induces skipping of cassette exons with short introns and weak splice sites, tending to change large protein domains. In THP-1 myeloid-like cells, SRRM2 depletion compromises cell viability, upregulates differentiation markers, and sensitizes cells to anti-leukemia drugs. SRRM2 induces a FES splice isoform that attenuates innate inflammatory responses, and MUC1 isoforms that undergo shedding with oncogenic properties. We conclude that SRRM2 acts as a scaffold to organize nuclear speckles, regulating alternative splicing in innate immunity and cell homeostasis.
SRRM2 是一种核斑点标记物，含有多个无序结构域，其功能障碍与多种人类疾病有关。我们主要使用 EGFP-SRRM2 敲入 HEK293T 细胞，证明了 SRRM2 形成了满足液-液相分离大多数特征的生物分子凝聚体，包括球形、动态重排、融合和体外实验支持的浓度依赖性。活细胞成像显示，SRRM2 沿着细胞周期组织核斑点。作为剪接体结构中存在的真正剪接因子，SRRM2 缺失会导致短内含子和弱剪接位点的盒式外显子跳跃，倾向于改变大的蛋白质结构域。在 THP-1 髓样样细胞中，SRRM2 的耗竭会降低细胞活力，上调分化标志物，并使细胞对白血病药物敏感。SRRM2 诱导 FES 剪接异构体，减弱固有免疫反应，以及具有致癌特性的发生脱落的 MUC1 异构体。我们得出结论，SRRM2 作为一种支架，调节固有免疫和细胞内稳态中的选择性剪接。
