The mammalian cell nucleus is a highly organized organelle that contains membrane-less structures referred to as nuclear bodies (NBs). Some NBs carry specific RNA types that play architectural roles in their formation. Here, we show two types of RNase-sensitive DBC1-containing NBs: DBC1 nuclear body (DNB) in HCT116 cells and Sam68 nuclear body (SNB) in HeLa cells that exhibit phase-separated features and are constructed using RNA polymerase I or II transcripts in a cell type-specific manner. We identified additional protein components present in DNB by immunoprecipitation-mass spectrometry, some of which (DBC1 and HNRNPL) are required for DNB formation. The rescue experiment using the truncated HNRNPL mutants revealed that two RNA-binding domains and intrinsically disordered regions of HNRNPL play significant roles in DNB formation. All these domains of HNRNPL promote in vitro droplet formation, suggesting the need for multivalent interactions between HNRNPL and RNA as well as proteins in DNB formation.

哺乳动物细胞核是一种高度组织化的细胞器，包含称为核体 (NB) 的无膜结构。一些 NB 携带特定的 RNA 类型，这些 RNA 类型在其形成中发挥建筑作用。在这里，我们展示了两种对 RNase 敏感的含 DBC1 的 NB：HCT116 细胞中的 DBC1 核体 (DNB) 和 HeLa 细胞中的 Sam68 核体 (SNB)，它们表现出相分离的特征并使用 RNA 聚合酶 I 或 II 转录物构建以特定于细胞类型的方式。我们通过免疫沉淀质谱法鉴定了 DNB 中存在的其他蛋白质成分，其中一些（DBC1 和 HNRNPL）是 DNB 形成所必需的。使用截短的 HNRNPL 突变体进行的拯救实验表明，HNRNPL 的两个 RNA 结合结构域和内在无序区域在 DNB 形成中起重要作用。体外液滴形成，表明 HNRNPL 和 RNA 以及 DNB 形成中的蛋白质之间需要多价相互作用。