ABSTRACT Eukaryotic cells have 2 to 3 discrete nucleoli required for ribosome synthesis. Nucleoli are phase separated nuclear sub-organelles. Here we examined the role of nuclear Lamins and nucleolar factors in modulating the compartmentalization and dynamics of histone 2B (H2B-ECFP) in the nucleolus. Live imaging and Fluorescence Recovery After Photobleaching (FRAP) of labelled H2B, showed that the depletion of Lamin B1, Fibrillarin (FBL) or Nucleostemin (GNL3), enhances H2B-ECFP mobility in the nucleolus. Furthermore, Nucleolin knockdown significantly decreases H2B-ECFP compartmentalization in the nucleolus, while H2B-ECFP residence and mobility in the nucleolus was prolonged upon Nucleolin overexpression. Co-expression of N-terminal and RNA binding domain (RBD) deletion mutants of Nucleolin or inhibiting 45S rRNA synthesis reduces the sequestration of H2B-ECFP in the nucleolus. Taken together, these studies reveal a crucial role of Nucleolin-rRNA complex in modulating the compartmentalization, stability and dynamics of H2B within the nucleolus.

中文翻译：

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核仁素调节核仁中组蛋白 2B-ECFP 的区室化和动力学

摘要 真核细胞有 2 到 3 个核糖体合成所需的离散核仁。核仁是相分离的核亚细胞器。在这里，我们检查了核层粘连蛋白和核仁因子在调节核仁中组蛋白 2B (H2B-ECFP) 的区室化和动力学中的作用。标记的 H2B 光漂白 (FRAP) 后的实时成像和荧光恢复表明，层粘连蛋白 B1、原纤维蛋白 (FBL) 或核骨蛋白 (GNL3) 的消耗增强了核仁中 H2B-ECFP 的迁移率。此外，核仁蛋白敲低显着降低了核仁中 H2B-ECFP 的区室化，而核仁蛋白过表达后，核仁中的 H2B-ECFP 驻留和流动性延长。核仁蛋白的 N 末端和 RNA 结合域 (RBD) 缺失突变体的共表达或抑制 45S rRNA 合成可减少核仁中 H2B-ECFP 的隔离。总之，这些研究揭示了 Nucleolin-rRNA 复合物在调节核仁内 H2B 的区室化、稳定性和动力学方面的关键作用。