Cellular Reorganization during Mitotic Entry

Temporal and spatial regulation of the small GTPase RhoA is a key element in triggering the disintegration of focal adhesions and the assembly of the actomyosin cortex during mitotic entry. Mitotic rounding generates optimal cell geometry for spindle assembly. The increase in cell volume and hydrostatic cell pressure generate forces against the environment of the cell. Cellular organelles undergo drastic and rapid changes in organization, shape, and number. Multiple mechanisms ensure that endomembranes do not interfere with spindle assembly. Defects in the mitotic reorganization of organelles can affect mitotic entry, chromosome segregation, organellar inheritance, and cell fate. The preparation of eukaryotic cells for division requires an extensive cellular reorganization, affecting cytoskeletal elements, chromatin, and organelles. These drastic changes in cellular architecture ensure the proper segregation of chromosomes and inheritance of organelles. The morphological alterations occurring during mitotic entry are tightly coordinated with the cell cycle, mainly through the action of mitotic kinases. Conversely, the fidelity of these processes impacts mitotic progression and is important for organismal homeostasis and cell fate. Here, we provide an overview of major architectural changes observed during early mitosis and review recent progress in understanding their regulatory mechanisms, focusing on processes accompanying mitotic cell rounding and restructuring of organelles in mammalian cells. The preparation of eukaryotic cells for division requires an extensive cellular reorganization, affecting cytoskeletal elements, chromatin, and organelles. These drastic changes in cellular architecture ensure the proper segregation of chromosomes and inheritance of organelles. The morphological alterations occurring during mitotic entry are tightly coordinated with the cell cycle, mainly through the action of mitotic kinases. Conversely, the fidelity of these processes impacts mitotic progression and is important for organismal homeostasis and cell fate. Here, we provide an overview of major architectural changes observed during early mitosis and review recent progress in understanding their regulatory mechanisms, focusing on processes accompanying mitotic cell rounding and restructuring of organelles in mammalian cells. a rigid and plastic layer of actin filaments, actin-binding proteins, and myosin motors underneath the plasma membrane. uses the deflection of a laser beam to measure force-induced changes in the position of a cantilever. AFM is not only applied for imaging of surfaces, but also to measure forces and for manipulation of objects. a small, abundant, homodimeric protein that is associated with chromatin and has many binding partners, among them LEM domain proteins. a monitoring system coupled to a negative-feedback mechanism that prevents progression into the next phase of the cell cycle if errors are detected. the first of distinct types of NLS to be discovered. It comprises a cluster of basic amino acids, recognized by the nuclear import adaptor protein importin α. members of a conserved family of large GTPases that use self-oligomerization to drive membrane scission events. ezrin, radixin, and moesin family of cytosolic actin-binding proteins that crosslink actin filaments to the plasma membrane. a protein family with formin homology domains that associate with the fast-growing end of actin filaments and promote actin polymerization; often effectors of RhoA. members of the Lamina-associated polypeptide 2 (LAP2)–Emerin–MAN1 (LEM) domain protein family of inner nuclear membrane and intranuclear proteins. The LEM domain is a protein module of about 40 amino acids, containing two parallel alpha helices. bridge the NE and couple the nucleus to the cytoskeleton. They comprise SUN domain proteins in the inner nuclear membrane and KASH domain proteins in the outer nuclear membrane, which interact with each other in the perinuclear space. a type V intermediate filament network comprising A-type and B-type lamin proteins underlying the NE of metazoan cells. large, macromolecular assemblies embedded in the NE, which serve as gateways for receptor-mediated nucleocytoplasmic transport and define the size limit for passive diffusion across the NE. the collective name for the about 30 distinct protein constituents of NPCs. cellular factors that determine the polarization of a group of cells or structures in the plane of an epithelium or tissue. contractile actomyosin bundles comprising approximately 10–30 actin filaments, which are crosslinked together by α-actinin. They often associate with focal adhesions.