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Cell Cycle (Georgetown, Tex.) 2015The DEK gene encodes a nuclear protein that binds chromatin and is involved in various fundamental nuclear processes including transcription, RNA splicing, DNA...
The DEK gene encodes a nuclear protein that binds chromatin and is involved in various fundamental nuclear processes including transcription, RNA splicing, DNA replication and DNA repair. Several cancer types characteristically over-express DEK at the earliest stages of transformation. In order to explore relevant mechanisms whereby DEK supports oncogenicity, we utilized cancer databases to identify gene transcripts whose expression patterns are tightly correlated with that of DEK. We identified an enrichment of genes involved in mitosis and thus investigated the regulation and possible function of DEK in cell division. Immunofluorescence analyses revealed that DEK dissociates from DNA in early prophase and re-associates with DNA during telophase in human keratinocytes. Mitotic cell populations displayed a sharp reduction in DEK protein levels compared to the corresponding interphase population, suggesting DEK may be degraded or otherwise removed from the cell prior to mitosis. Interestingly, DEK overexpression stimulated its own aberrant association with chromatin throughout mitosis. Furthermore, DEK co-localized with anaphase bridges, chromosome fragments, and micronuclei, suggesting a specific association with mitotically defective chromosomes. We found that DEK over-expression in both non-transformed and transformed cells is sufficient to stimulate micronucleus formation. These data support a model wherein normal chromosomal clearance of DEK is required for maintenance of high fidelity cell division and chromosomal integrity. Therefore, the overexpression of DEK and its incomplete removal from mitotic chromosomes promotes genomic instability through the generation of genetically abnormal daughter cells. Consequently, DEK over-expression may be involved in the initial steps of developing oncogenic mutations in cells leading to cancer initiation.
Topics: Anaphase; Aneuploidy; Animals; Blotting, Western; Cell Division; Cell Nucleus; Chromatin; Chromosomal Instability; Chromosomal Proteins, Non-Histone; Chromosomes; Flow Cytometry; Humans; Interphase; Mice; Mitosis; Oncogene Proteins; Poly-ADP-Ribose Binding Proteins; Prophase; Telophase
PubMed: 25945971
DOI: 10.1080/15384101.2015.1044177 -
Cell Reports May 2020Centrosome separation in late G2/ early prophase requires precise spatial coordination that is determined by a balance of forces promoting and antagonizing separation....
Centrosome separation in late G2/ early prophase requires precise spatial coordination that is determined by a balance of forces promoting and antagonizing separation. The major effector of centrosome separation is the kinesin Eg5. However, the identity and regulation of Eg5-antagonizing forces is less well characterized. By manipulating candidate components, we find that centrosome separation is reversible and that separated centrosomes congress toward a central position underneath the flat nucleus. This positioning mechanism requires microtubule polymerization, as well as actin polymerization. We identify perinuclear actin structures that form in late G2/early prophase and interact with microtubules emanating from the centrosomes. Disrupting these structures by breaking the interactions of the linker of nucleoskeleton and cytoskeleton (LINC) complex with perinuclear actin filaments abrogates this centrosome positioning mechanism and causes an increase in subsequent chromosome segregation errors. Our results demonstrate how geometrical cues from the cell nucleus coordinate the orientation of the emanating spindle poles before nuclear envelope breakdown.
Topics: Actins; Centrosome; Chromosome Segregation; Humans; Prophase
PubMed: 32460023
DOI: 10.1016/j.celrep.2020.107681 -
Current Topics in Developmental Biology 1998Meiotic division comprises a complex series of events, many of which are unique in the life cycle of the organism. The process utilizes both proteins that participate in... (Review)
Review
Meiotic division comprises a complex series of events, many of which are unique in the life cycle of the organism. The process utilizes both proteins that participate in normal mitotic cell cycle progression and DNA damage repair and proteins expressed only during meiosis. Until recently, few meiotic protein participants had been identified and characterized, but several recent developments have changed this situation. Proteins can be selected for study based on their cDNA sequence and similarity to known proteins with "suspicious" repair/recombination or cell cycle activity and antibodies against these proteins applied to meiotic nuclei to test for activity. With the development of gene sequence data bases from many organisms, similarity to a known protein need not be based on the same or even a closely related species. Potential interactions between two or more proteins can be identified and involvement in a common process inferred based on antibody colocalization. The gene sequence can be disrupted and the effect on meiotic progression directly examined. Previously identified structures, the synaptonemal complex (SC) and both early and late recombination nodules (RNs), provide structural and temporal landmarks that assist in inferring meiotic activity of the protein being studied. Mammalian meiosis is especially attractive for these kinds of studies since spermatocyte and oocyte nuclei are large with distinct nuclear organelles and since meiosis is highly protracted, occurring over a period of several days. In this chapter, an approach to the study of mammalian meiosis based on use of specific antibodies is outlined and methods of coupling this approach to other techniques, such as targeted gene disruption or chromosome aberrations, are described. Some of the proteins already identified as participants in meiotic prophase are reviewed and their presumed functions discussed.
Topics: Animals; DNA-Binding Proteins; Fungal Proteins; Genetic Diseases, Inborn; Immunohistochemistry; Meiosis; Mice; Prophase; Proteins; Rad51 Recombinase; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins
PubMed: 9352187
DOI: 10.1016/s0070-2153(08)60175-1 -
PLoS Genetics Apr 2017The meiosis-specific chromosomal events of homolog pairing, synapsis, and recombination occur over an extended meiotic prophase I that is many times longer than prophase...
The meiosis-specific chromosomal events of homolog pairing, synapsis, and recombination occur over an extended meiotic prophase I that is many times longer than prophase of mitosis. Here we show that, in mice, maintenance of an extended meiotic prophase I requires the gene Meioc, a germ-cell specific factor conserved in most metazoans. In mice, Meioc is expressed in male and female germ cells upon initiation of and throughout meiotic prophase I. Mouse germ cells lacking Meioc initiate meiosis: they undergo pre-meiotic DNA replication, they express proteins involved in synapsis and recombination, and a subset of cells progress as far as the zygotene stage of prophase I. However, cells in early meiotic prophase-as early as the preleptotene stage-proceed to condense their chromosomes and assemble a spindle, as if having progressed to metaphase. Meioc-deficient spermatocytes that have initiated synapsis mis-express CYCLIN A2, which is normally expressed in mitotic spermatogonia, suggesting a failure to properly transition to a meiotic cell cycle program. MEIOC interacts with YTHDC2, and the two proteins pull-down an overlapping set of mitosis-associated transcripts. We conclude that when the meiotic chromosomal program is initiated, Meioc is simultaneously induced so as to extend meiotic prophase. Specifically, MEIOC, together with YTHDC2, promotes a meiotic (as opposed to mitotic) cell cycle program via post-transcriptional control of their target transcripts.
Topics: Animals; Cell Cycle Proteins; Chromosome Pairing; Cyclin A2; Gene Expression Regulation, Developmental; Male; Meiosis; Mice; Mitosis; Prophase; RNA-Binding Proteins; Spermatocytes; Spermatogenesis; Spermatogonia
PubMed: 28380054
DOI: 10.1371/journal.pgen.1006704 -
The Plant Journal : For Cell and... Jul 2013In plants, as in all eukaryotic organisms, microtubule- and actin-filament based structures play fundamental roles during cell division. In addition to the mitotic... (Review)
Review
In plants, as in all eukaryotic organisms, microtubule- and actin-filament based structures play fundamental roles during cell division. In addition to the mitotic spindle, plant cells have evolved a unique cytoskeletal structure that designates a specific division plane before the onset of mitosis via formation of a cortical band of microtubules and actin filaments called the preprophase band. During cytokinesis, a second plant-specific microtubule and actin filament structure called the phragmoplast directs vesicles to create the new cell wall. In response to intrinsic and extrinsic cues, many plant cells form a preprophase band in G2 , then the preprophase band recruits specific proteins to populate the cortical division site prior to disassembly of the preprophase band in prometaphase. These proteins are thought to act as a spatial reminder that actively guides the phragmoplast towards the cortical division site during cytokinesis. A number of proteins involved in determination and maintenance of the plane of cell division have been identified. Our current understanding of the molecular interactions of these proteins and their regulation of microtubules is incomplete, but advanced imaging techniques and computer simulations have validated some early concepts of division site determination.
Topics: Actin Cytoskeleton; Arabidopsis; Bryopsida; Cell Division; Cell Wall; Cytokinesis; Cytoskeleton; Microtubules; Mitosis; Plant Cells; Plant Proteins; Prophase; Tradescantia; Zea mays
PubMed: 23496276
DOI: 10.1111/tpj.12177 -
Molecular Biology of the Cell Aug 2022The Chromosome Passenger Complex (CPC) generates chromosome autonomous signals that regulate mitotic events critical for genome stability. Tip60 is a lysine...
The Chromosome Passenger Complex (CPC) generates chromosome autonomous signals that regulate mitotic events critical for genome stability. Tip60 is a lysine acetyltransferase that is a tumor suppressor and is targeted for proteasomal degradation by oncogenic papilloma viruses. Mitotic regulation requires the localization of the CPC to inner centromeres, which is driven by the Haspin kinase phosphorylating histone H3 on threonine 3 (H3T3ph). Here we describe how Tip60 acetylates histone H3 at lysine 4 (H3K4ac) to block both the H3T3ph writer and the reader to ensure that this mitotic signaling cannot begin before prophase. Specifically, H3K4ac inhibits Haspin phosphorylation of H3T3 and prevents binding of the Survivin subunit to H3T3ph. Tip60 acetylates H3K4 during S/G2 at centromeres. Inhibition of Tip60 allows the CPC to bind centromeres in G2 cells, and targeting of Tip60 to centromeres prevents CPC localization in mitosis. The H3K4ac mark is removed in prophase by HDAC3 to initiate the CPC localization cascade. Together, our results suggest that Tip60 and HDAC3 temporally control H3K4 acetylation to precisely time the targeting of the CPC to inner centromeres.
Topics: Acetylation; Centromere; Histones; Intracellular Signaling Peptides and Proteins; Mitosis; Phosphorylation; Protein Serine-Threonine Kinases; Threonine
PubMed: 35653296
DOI: 10.1091/mbc.E21-06-0283 -
PLoS Genetics May 2018Condensin complexes are key determinants of higher-order chromatin structure and are required for mitotic and meiotic chromosome compaction and segregation. We...
Condensin complexes are key determinants of higher-order chromatin structure and are required for mitotic and meiotic chromosome compaction and segregation. We identified a new role for condensin in the maintenance of sister chromatid cohesion during C. elegans meiosis. Using conventional and stimulated emission depletion (STED) microscopy we show that levels of chromosomally-bound cohesin were significantly reduced in dpy-28 mutants, which lack a subunit of condensin I. SYP-1, a component of the synaptonemal complex central region, was also diminished, but no decrease in the axial element protein HTP-3 was observed. Surprisingly, the two key meiotic cohesin complexes of C. elegans were both depleted from meiotic chromosomes following the loss of condensin I, and disrupting condensin I in cohesin mutants increased the frequency of detached sister chromatids. During mitosis and meiosis in many organisms, establishment of cohesion is antagonized by cohesin removal by Wapl, and we found that condensin I binds to C. elegans WAPL-1 and counteracts WAPL-1-dependent cohesin removal. Our data suggest that condensin I opposes WAPL-1 to promote stable binding of cohesin to meiotic chromosomes, thereby ensuring linkages between sister chromatids in early meiosis.
Topics: Adenosine Triphosphatases; Animals; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Cell Cycle Proteins; Chromatids; Chromosomal Proteins, Non-Histone; Chromosome Segregation; DNA-Binding Proteins; In Situ Hybridization, Fluorescence; Intercellular Signaling Peptides and Proteins; Meiosis; Multiprotein Complexes; Mutation; Nuclear Proteins; RNA Interference; Synaptonemal Complex; Cohesins
PubMed: 29768402
DOI: 10.1371/journal.pgen.1007382 -
Mechanisms of Development Oct 2018Germline stem cells are maintained in the distal region of the C. elegans gonad. These cells undergo mitotic divisions, and GLP-1/Notch signaling dictates whether they...
Germline stem cells are maintained in the distal region of the C. elegans gonad. These cells undergo mitotic divisions, and GLP-1/Notch signaling dictates whether they remain in this state. The somatic distal tip cell (DTC) caps the end of the distal gonad and is essential for maintenance of the germline mitotic zone. As germ cells move away from the DTC they exit mitosis and enter early meiotic prophase. Here we identify the Period protein homolog LIN-42 as a new regulator of germline development in C. elegans. LIN-42 is expressed in almost all somatic cells including the DTC, and LIN-42 functions as a transcription factor in the heterochronic pathway and to regulate molting. We found that the mitotic proliferative zone size in the distal gonad was significantly reduced by ~25% in lin-42 mutants compared to WT N2 worms. A lin-42 mutation also reduced the mitotic proliferative zone size caused by glp-1 partial loss-of-function and gain-of-function alleles. LIN-42 mediates this effect, at least in part, by regulating expression of the GLP-1/Notch ligand LAG-2. We further show that lin-42 expression itself is regulated by ATX-2, which promotes germline proliferation and is the homolog of the RNA binding protein ataxin-2 that is implicated in human neurodegenerative diseases. Altogether our results establish a new role for the conserved, important Period protein homolog LIN-42 in regulating early germline development. These results also suggest that in addition to regulating behavioral rhythms, the circadian clock plays an important role in communicating environmental signals to essential reproductive pathways.
Topics: Animals; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Gene Expression Regulation, Developmental; Germ Cells; Mitosis; Period Circadian Proteins; Phenotype; Receptors, Notch; Signal Transduction; Transcription Factors; Transcription, Genetic
PubMed: 30144508
DOI: 10.1016/j.mod.2018.08.008 -
Heliyon Jul 2019Imidacloprid (IMI) is a neonicotinoid insecticide widely used in agricultural activities all around the world. This compound is transported from croplands to surrounding...
Imidacloprid (IMI) is a neonicotinoid insecticide widely used in agricultural activities all around the world. This compound is transported from croplands to surrounding freshwater ecosystems, producing adverse effects on non-target organisms. Because of the relevance of aquatic macrophytes in the above-mentioned environments and the lack of studies of potential effects of IMI on them, this work aimed to assess the mitotic process and potential genotoxicity in the aquatic macrophyte L. Although the analysis of the Mitotic Index (MI) showed that IMI was not cytotoxic, the Cell Proliferation Kinetics (CPK) frequencies evidenced modifications in the kinetics of the mitotic process. Indeed, the anaphases ratio decreased at 10 and 100 μg/L IMI, while at 1000 μg/L an increase of prophases ratio and a decrease of metaphases ratio were observed. Regarding genotoxicity, IMI produced an increase of the abnormal metaphases frequency from 10 μg/L to 1000 μg/L as well as an increase in clastogenic anaphases-telophases frequency at 100 and 1000 μg/L. In addition, aneugenic anaphases-telophases and C-mitosis frequencies also increased at 1000 μg/L, confirming the effects on the mitotic spindle. Considering the genotoxic effects on through two different mechanisms (aneugenic and clastogenic) and the wide spread use of IMI in agriculture, these mechanisms of toxicity on macrophytes should be considered among other recognized effects of this insecticide on aquatic biota.
PubMed: 31372562
DOI: 10.1016/j.heliyon.2019.e02118 -
Current Biology : CB Apr 2010Centrosome separation, critical for bipolar spindle formation and subsequent chromosome segregation during mitosis, occurs via distinct prophase and prometaphase...
Centrosome separation, critical for bipolar spindle formation and subsequent chromosome segregation during mitosis, occurs via distinct prophase and prometaphase pathways. Kinesin-5 (Eg5), a microtubule (MT) motor, pushes centrosomes apart during bipolar spindle assembly; its suppression results in monopolar spindles and mitotic arrest. Forces that antagonize Eg5 in prophase are unknown. Here we identify a new force generating mechanism mediated by the guanine nucleotide exchange factor (GEF) Tiam1, dependent on its ability to activate the GTPase Rac. We reveal that Tiam1 and Rac localize to centrosomes during prophase and prometaphase, and Tiam1, acting through Rac, ordinarily retards centrosome separation. Importantly, both Tiam1-depleted cells in culture and Rac1-deficient epithelial cells in vivo escape the mitotic arrest induced by Eg5 suppression. Moreover, Tiam1-depleted cells transit more slowly through prometaphase and display increased chromosome congression errors. Significantly, Eg5 suppression in Tiam1-depleted cells rectifies not only their increased centrosome separation but also their chromosome congression errors and mitotic delay. These findings identify Tiam1-Rac signaling as the first antagonist of centrosome separation during prophase, demonstrate its requirement in balancing Eg5-induced forces during bipolar spindle assembly in vitro and in vivo, and show that proper centrosome separation in prophase facilitates subsequent chromosome congression.
Topics: Animals; Base Sequence; Cell Line; Centrosome; Chromosome Segregation; Dogs; Guanine Nucleotide Exchange Factors; Kinesins; Mice; Mice, Inbred C57BL; Mice, Transgenic; Mitosis; Models, Biological; Neuropeptides; RNA Interference; Signal Transduction; Spindle Apparatus; rac GTP-Binding Proteins; rac1 GTP-Binding Protein
PubMed: 20346677
DOI: 10.1016/j.cub.2010.02.033