title: Asynchronous nuclear division cycles in multinucleated cells.
abstract: Synchronous mitosis is common in multinucleated cells. We analyzed a unique asynchronous nuclear division cycle in a multinucleated filamentous fungus, Ashbya gossypii. Nuclear pedigree analysis and observation of GFP-labeled spindle pole bodies demonstrated that neighboring nuclei in A. gossypii cells are in different cell cycle stages despite close physical proximity. Neighboring nuclei did not differ significantly in their patterns of cyclin protein localization such that both G1 and mitotic cyclins were present regardless of cell cycle stage, suggesting that the complete destruction of cyclins is not occurring in this system. Indeed, the expression of mitotic cyclin lacking NH(2)-terminal destruction box sequences did not block cell cycle progression. Cells lacking AgSic1p, a predicted cyclin-dependent kinase (CDK) inhibitor, however, showed aberrant multipolar spindles and fragmented nuclei that are indicative of flawed mitoses. We hypothesize that the continuous cytoplasm in these cells promoted the evolution of a nuclear division cycle in which CDK inhibitors primarily control CDK activity rather than oscillating mitotic cyclin proteins.
authors.affiliation: Department of Molecular Microbiology, Biozentrum University of Basel, 4056 Basel, Switzerland. amy.gladfelter@unibas.ch
authors.forename: Amy S
authors.initials: AS
authors.lastname: Gladfelter
authors.forename: A Katrin
authors.initials: AK
authors.lastname: Hungerbuehler
authors.forename: Peter
authors.initials: P
authors.lastname: Philippsen
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology; D002453:Cell Cycle / Q000235:genetics / Q000502:physiology; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism*; D048750:Cell Nucleus Division / Q000235:genetics / Q000502:physiology*; D019926:Cyclin B / Q000235:genetics / Q000378:metabolism; D056746:Cyclin G; D050756:Cyclin-Dependent Kinase Inhibitor Proteins / Q000235:genetics / Q000378:metabolism; D016213:Cyclins / Q000235:genetics / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000032:analysis; D005656:Fungal Proteins / Q000032:analysis; D006657:Histones / Q000032:analysis; D008938:Mitosis / Q000235:genetics / Q000502:physiology; D009154:Mutation / Q000235:genetics; D049790:Nuclear Export Signals / Q000235:genetics; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D004718:Saccharomycetales / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D008941:Spindle Apparatus / Q000737:chemistry / Q000502:physiology
chemical_list: C082719:CLN1 protein, S cerevisiae; D018797:Cell Cycle Proteins; D019926:Cyclin B; D056746:Cyclin G; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; D016213:Cyclins; D003598:Cytoskeletal Proteins; D005656:Fungal Proteins; D006657:Histones; D049790:Nuclear Export Signals; D029701:Saccharomyces cerevisiae Proteins; C099685:SWE1 protein, S cerevisiae; D011505:Protein-Tyrosine Kinases