Guan Xin, Jiao Yang, Chen Lingling, Li Xiliang, Shang Guangbin, Wang Fengcai, Feng Yunpeng, Jiao Mingda
School of Life Sciences, Northeast Normal University, Changchun, Jilin Province, 130024, China.
Key Laboratory of Modern Preparation of Traditional Chinese Medicine, Ministry of Education, Jiangxi University of Traditional Chinese Medicine, Nanchang, Jiangxi Province, 330004, China.
Cell Biol Int. 2017 Mar;41(3):258-266. doi: 10.1002/cbin.10719. Epub 2017 Jan 24.
In the higher eukaryotic nucleolus, fibrillar centers (FCs), the dense fibrillar components (DFCs), and the granular components (GCs) are functional domains structurally relatively well-defined by electron microscopy (EM). However, ultrastructural alterations in FC, DFC, and GC during the cell cycle and their associated cellular functions are still largely unclear. Based on synchronized HeLa cells, we followed the structural dynamics of nucleolus during cell cycle by EM. We found that nucleolus structure shifted from tripartite to bipartite organization and FC/DFCs were reorganized in S phase with three distinct stages: (1) In early-S phase, FC/DFC structures were disassembled. (2) In mid-S phase, a transition from FC/DFC disruption to restoration occurred. As FC/DFC structures were completely disassembled, nucleoli became structurally homogenous. (3) In late-S phase, the number of small FC/DFCs increased and subsequently large FC/DFCs were constructed. Our data demonstrated that nucleolar FC/DFCs in interphase are presented in two different forms or states due to disassembly and reassembly. FC/DFCs in G1 are nucleolar structures constructed concomitantly with the establishment of nucleoli derived from the nucleolar organizer region (NOR). FC/DFCs in G2 are nucleolar components reconstituted after the global reassembly in mid-S phase. Dynamic nucleolus structures revealed in this study may serve as ultrastructural characteristics to reflect distinct stages of the cell cycle. By providing evidence for the temporal and spatial regulation of nucleolus, our findings contribute to the coupling of nucleolus structures to cell cycle dependent functions.
在高等真核生物的核仁中，纤维中心（FCs）、致密纤维组分（DFCs）和颗粒组分（GCs）是通过电子显微镜（EM）在结构上相对明确的功能域。然而，在细胞周期中FC、DFC和GC的超微结构变化及其相关的细胞功能仍 largely不清楚。基于同步化的HeLa细胞，我们通过EM追踪了细胞周期中核仁的结构动态。我们发现核仁结构从三分体组织转变为二分体组织，并且FC/DFCs在S期经历了三个不同阶段的重组：（1）在S期早期，FC/DFC结构被拆解。（2）在S期中段，发生了从FC/DFC破坏到恢复的转变。随着FC/DFC结构完全被拆解，核仁在结构上变得均匀一致。（3）在S期后期，小的FC/DFCs数量增加，随后大的FC/DFCs被构建。我们的数据表明，由于拆解和重新组装，间期核仁中的FC/DFCs以两种不同的形式或状态呈现。G1期的FC/DFCs是与源自核仁组织区（NOR）的核仁建立同时构建的核仁结构。G2期的FC/DFCs是在S期中段全局重新组装后重新构成的核仁组分。本研究中揭示的动态核仁结构可能作为超微结构特征来反映细胞周期的不同阶段。通过为核仁的时空调节提供证据，我们的发现有助于核仁结构与细胞周期依赖性功能的耦合。
