title: Disruption and restoration of nucleolar FC and DFC during S phase in HeLa cells.
abstract: 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.
authors.affiliation: School of Life Sciences, Northeast Normal University, Changchun, Jilin Province, 130024, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Guan
authors.affiliation: School of Life Sciences, Northeast Normal University, Changchun, Jilin Province, 130024, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Jiao
authors.affiliation: School of Life Sciences, Northeast Normal University, Changchun, Jilin Province, 130024, China.
authors.forename: Lingling
authors.initials: L
authors.lastname: Chen
authors.affiliation: School of Life Sciences, Northeast Normal University, Changchun, Jilin Province, 130024, China.
authors.forename: Xiliang
authors.initials: X
authors.lastname: Li
authors.affiliation: Key Laboratory of Modern Preparation of Traditional Chinese Medicine, Ministry of Education, Jiangxi University of Traditional Chinese Medicine, Nanchang, Jiangxi Province, 330004, China.
authors.forename: Guangbin
authors.initials: G
authors.lastname: Shang
authors.affiliation: Jiu Jiang University, Jiangxi Province, 332000, China.
authors.forename: Fengcai
authors.initials: F
authors.lastname: Wang
authors.affiliation: School of Life Sciences, Northeast Normal University, Changchun, Jilin Province, 130024, China.|The Key Laboratory of Molecular Epigenetics of Ministry of Education (MOE), Northeast Normal University, Changchun, Jilin Province, 130024, China.
authors.forename: Yunpeng
authors.initials: Y
authors.lastname: Feng
authors.affiliation: School of Life Sciences, Northeast Normal University, Changchun, Jilin Province, 130024, China.
authors.forename: Mingda
authors.initials: M
authors.lastname: Jiao
mesh_terms: D002466:Cell Nucleolus / Q000502:physiology* / Q000648:ultrastructure*; D006367:HeLa Cells; D006801:Humans; D016196:S Phase / Q000502:physiology*
keywords: FC/DFC unit; bipartite/tripartite; cell cycle; nucleolus; reorganization