Transcription-templated assembly of the nucleolus in the Caenorhabditis elegans embryo

• 成果类型: Article
• 署名作者: Kodan, Nishant; Hussaini, Rabeya; Weber, Stephanie C.; Kondev, Jane; Mohapatra, Lishibanya
• 署名单位: Rochester Institute of Technology; New York University; McGill University; McGill University; Brandeis University
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-10558
• DOI: 10.1073/pnas.2411964122
• 发表日期: 2025-05-30
• 关键词: rna; size; germline; roles; gene

摘要

The nucleolus is a multicomponent structure made of RNA and proteins that serves as the site of ribosome biogenesis within the nucleus. It has been extensively studied as a prototype of a biomolecular condensate whose assembly is driven by phase separation. While the steady-state size of the nucleolus is quantitatively accounted for by the thermodynamics of phase separation, we show that experimental measurements of the assembly dynamics are inconsistent with a simple model of a phase-separating system relaxing to its equilibrium state. Instead, we show that the dynamics are well described by a model in which the transcription of ribosomal RNA actively drives nucleolar assembly. We find that our model of active transcription-templated assembly quantitatively accounts for the rapid kinetics observed in early embryos at different developmental stages, and for different RNA interference (RNAi) perturbations of embryo size. Our model predicts a scaling of the time to assembly with the volume of the nucleus to the one-third power, which is confirmed by experimental data. Our study highlights the role of active processes such as transcription in controlling the placement and timing of assembly of membraneless organelles.