Biochemical, proteomic and microscopic insights into regulation of nucleolar structure and function

哺乳动物核核是一种非膜结合的核细胞器，在核糖体DNA串联重复序列周围形成，并以其在核糖体生物发生协调中的重要作用而闻名，核糖体为细胞提供蛋白质合成所需的核糖体复合物。这种结构是动态的，在哺乳动物细胞的每个细胞周期中都有分解和重组，并在各种细胞应力的作用下重组其内部结构。***最近的生物化学和蛋白质组学分析揭示了核仁功能复杂性比以前所认识到的要广泛得多，将这种细胞器与细胞周期调节、DNA损伤修复、端粒代谢、RNA加工和细胞对各种应激反应的协调联系起来。鉴于核仁功能障碍与多种疾病状态有关，包括癌症、加速衰老和病毒感染，很明显，这些不同个体途径的精确协调对于其正常功能至关重要。***尽管近年来取得了重大进展，包括更详细的核仁蛋白，DNA和RNA成分目录，但关于哪些特定因素提供核仁结构完整性以及如何调节其动态组织的重要问题仍有待回答。关于发生在核仁内部或涉及核仁的全部生物过程，以及亚核仁结构与分子水平上的特定功能之间的关系，还有很多有待了解。***我们的兴趣主要在于非规范核核成分（即那些不直接参与核糖体生物发生的成分）的结构/功能关系，我们假设它们的功能符合一个定义的结构，类似于观察到的参与核糖体生物发生途径的成分的结构/功能关系。因此，本项目的主要目标是表征介导非核糖体功能的核仁蛋白，并定义该细胞器协调组织的调节机制，我们建议将强大的新超分辨率成像和定量蛋白质组学技术相结合来进行这些研究。***了解核仁组装/维持和功能的调控仍然是细胞生物学的一个基本问题。鉴于核仁蛋白质含量的详细描述在过去几年中已经出现，但我们仍然不知道它们的各种功能是如何被调节的（在某些情况下，它们的实际功能是什么），这种结构显然仍然是重要新发现的来源，毫无疑问，在可预见的未来会有更多的惊喜。* * * * *

The mammalian nucleolus is a non membrane-bound nuclear organelle that forms around tandem repeats of ribosomal DNA and is best known for its essential role in the coordination of ribosome biogenesis, which supplies the cell with the ribosome complexes required for protein synthesis. This structure is dynamic, disassembling and reassembling throughout each cell cycle in mammalian cells and reorganizing its internal structure in response to various cellular stresses. ***Recent biochemical and proteomic analyses have revealed a much wider nucleolar functional complexity than was previously appreciated, linking this organelle to roles in cell cycle regulation, DNA damage repair, telomere metabolism, RNA processing and coordination of the cellular response to various stresses. Given that nucleolar dysfunction has been linked to several disease states, including cancer, accelerated aging and viral infection, it is clear that precise coordination of these diverse individual pathways is essential for its proper function.***    Despite major advances in recent years, including a more detailed catalogue of nucleolar protein, DNA and RNA components, important questions remain to be answered with regard to which specific factors provide the nucleolus with its structural integrity and how its dynamic organization is regulated. Much also remains to be learned about the full range of biological processes that occur within, or involve, the nucleolus, and the relationship between sub-nucleolar structure and specific functions at the molecular level.***    Our interest lies primarily in the structure/function relationship of non-canonical nucleolar components (i.e. those not involved directly in ribosome biogenesis), and we hypothesize that their functions fit within a defined architecture, similar to the structure/function relationship observed for components involved in ribosome biogenesis pathways. The main objectives of this project are thus to characterize nucleolar proteins that mediate non-ribosomal functions and define the regulatory mechanisms that underlie this organelle's coordinated organization, and we propose to apply a combination of powerful new super-resolution imaging and quantitative proteomic technologies to carry them out. ***    Understanding the regulation of nucleolar assembly/maintenance and function remains a fundamental question in cell biology. Given that a detailed description of the protein content of the nucleolus has emerged over the past few years and yet we still do not know how their diverse functions are regulated (and in some cases, what their functions actually are) this structure clearly remains a source of significant new discoveries and undoubtedly some more surprises for the foreseeable future. ***    **