scholarly journals Human cyclins A and B1 are differentially located in the cell and undergo cell cycle-dependent nuclear transport.

1991 ◽  
Vol 115 (1) ◽  
pp. 1-17 ◽  
Author(s):  
J Pines ◽  
T Hunter
Keyword(s):  
Cell Cycle ◽  
Human Fibroblasts ◽  
Nuclear Lamina ◽  
Cyclin A ◽  
Cyclin B1 ◽  
Cell Fractionation ◽  
Mitotic Apparatus ◽  
Epithelial Tumor ◽  
Mitotic Cyclin ◽  
Cycle Dependent

We have used immunofluorescence staining to study the subcellular distribution of cyclin A and B1 during the somatic cell cycle. In both primary human fibroblasts and in epithelial tumor cells, we find that cyclin A is predominantly nuclear from S phase onwards. Cyclin A may associated with condensing chromosomes in prophase, but is not associated with condensed chromosomes in metaphase. By contrast, cyclin B1 accumulates in the cytoplasm of interphase cells and only enters the nucleus at the beginning of mitosis, before nuclear lamina breakdown. In mitotic cells, cyclin B1 associates with condensed chromosomes in prophase and metaphase, and with the mitotic apparatus. Cyclin A is degraded during metaphase and cyclin B1 is precipitously destroyed at the metaphase----anaphase transition. Cell fractionation and immunoprecipitation studies showed that both cyclin A and cyclin B1 are associated with PSTAIRE-containing proteins. The nuclear, but not the cytoplasmic form, of cyclin A is associated with a 33-kD PSTAIRE-containing protein. Cyclin B1 is associated with p34cdc2 in the cytoplasm. Thus we propose that the different localization of cyclin A and cyclin B1 in the cell cycle could be the means by which the two types of mitotic cyclin confer substrate specificity upon their associated PSTAIRE-containing protein kinase subunit.

Cell cycle-dependent SUMO-1 conjugation to nuclear mitotic apparatus protein (NuMA)

2014 ◽  
Vol 443 (1) ◽  
pp. 259-265 ◽  
Author(s):  
Jae Sung Seo ◽  
Ha Na Kim ◽  
Sun-Jick Kim ◽  
Jiyoung Bang ◽  
Eun-A Kim ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Mitotic Apparatus ◽  
Nuclear Mitotic Apparatus ◽  
Cycle Dependent

Cell cycle‐dependent expression of cyclooxygenase‐2 in human fibroblasts

2000 ◽  
Vol 15 (2) ◽  
pp. 288-290 ◽  
Author(s):  
Derek W. Gilroy ◽  
Michael A. Saunders ◽  
Leticia Sansores‐Garcia ◽  
Nena Matijevic‐Aleksic ◽  
Kenneth K. Wu
Keyword(s):  
Cell Cycle ◽  
Human Fibroblasts ◽  
Cyclooxygenase 2 ◽  
Cycle Dependent

scholarly journals A 62-kD protein required for mitotic progression is associated with the mitotic apparatus during M-phase and with the nucleus during interphase.

1992 ◽  
Vol 119 (4) ◽  
pp. 843-854 ◽  
Author(s):  
J A Johnston ◽  
R D Sloboda
Keyword(s):  
Cell Cycle ◽  
Nuclear Envelope ◽  
Cellular Protein ◽  
Immunogold Electron Microscopy ◽  
Mitotic Apparatus ◽  
Surf Clam ◽  
Calcium Calmodulin Dependent ◽  
Protein Pool ◽  
Mitotic Cyclin

A protein of 62 kD is a substrate of a calcium/calmodulin-dependent protein kinase, and both proteins copurify with isolated mitotic apparatuses (Dinsmore, J. H., and R. D. Sloboda. 1988. Cell. 53:769-780). Phosphorylation of the 62-kD protein increases after fertilization; maximum incorporation of phosphate occurs during late metaphase and anaphase and correlates directly with microtubule disassembly as determined by in vitro experiments with isolated mitotic apparatuses. Because 62-kD protein phosphorylation occurs in a pattern similar to the accumulation of the mitotic cyclin proteins, experiments were performed to determine the relationship between cyclin and the 62-kD protein. Continuous labeling of marine embryos with [35S]methionine, as well as immunoblots of marine embryo proteins using specific antibodies, were used to identify both cyclin and the 62-kD protein. These results clearly demonstrate that the 62-kD protein is distinct from cyclin and, unlike cyclin, is a constant member of the cellular protein pool during the first two cell cycles in sea urchin and surf clam embryos. Similar results were obtained using immunofluorescence microscopy of intact eggs and embryos. In addition, immunogold electron microscopy reveals that the 62-kD protein associates with the microtubules of the mitotic apparatus in dividing cells. Interestingly, the protein changes its subcellular distribution with respect to microtubules during the cell cycle. Specifically, during mitosis the 62-kD protein associates with the mitotic apparatus; before nuclear envelope breakdown, however, the 62-kD protein is confined to the nucleus. After anaphase, the 62-kD protein returns to the nucleus, where it resides until nuclear envelope disassembly of the next cell cycle.

scholarly journals Cell cycle-dependent proteolysis and ectopic overexpression of cyclin B1 in tobacco BY2 cells

2000 ◽  
Vol 24 (6) ◽  
pp. 763-773 ◽  
Author(s):  
Marie Claire Criqui ◽  
Yves Parmentier ◽  
Aude Derevier ◽  
Wen-Hui Shen ◽  
Aiwu Dong ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cyclin B1 ◽  
Ectopic Overexpression ◽  
Cycle Dependent

Association of cyclin A and cdk2 with SV40 DNA in replication initiation complexes is cell cycle dependent

Chromosoma ◽  
1997 ◽  
Vol 105 (6) ◽  
pp. 349-359 ◽  
Author(s):  
Dominique Cannella ◽  
James M. Roberts ◽  
Rati Fotedar
Keyword(s):  
Cell Cycle ◽  
Cyclin A ◽  
Replication Initiation ◽  
Cycle Dependent ◽  
Sv40 Dna

scholarly journals p21-Mediated Nuclear Retention of Cyclin B1-Cdk1 in Response to Genotoxic Stress

2004 ◽  
Vol 15 (9) ◽  
pp. 3965-3976 ◽  
Author(s):  
Fabienne Baus Charrier-Savournin ◽  
Marie-Thérèse Château ◽  
Véronique Gire ◽  
John Sedivy ◽  
Jacques Piette ◽  
...  
Keyword(s):  
Dna Damage ◽  
Current Model ◽  
Human Fibroblasts ◽  
Genotoxic Stress ◽  
Cyclin B1 ◽  
Nuclear Accumulation ◽  
G2 Arrest ◽  
Nuclear Retention ◽  
Mitotic Cyclin ◽  
Normal Human

G2 arrest of cells suffering DNA damage in S phase is crucial to avoid their entry into mitosis, with the concomitant risks of oncogenic transformation. According to the current model, signals elicited by DNA damage prevent mitosis by inhibiting both activation and nuclear import of cyclin B1-Cdk1, a master mitotic regulator. We now show that normal human fibroblasts use additional mechanisms to block activation of cyclin B1-Cdk1. In these cells, exposure to nonrepairable DNA damage leads to nuclear accumulation of inactive cyclin B1-Cdk1 complexes. This nuclear retention, which strictly depends on association with endogenous p21, prevents activation of cyclin B1-Cdk1 by Cdc25 and Cdk-activating kinase as well as its recruitment to the centrosome. In p21-deficient normal human fibroblasts and immortal cell lines, cyclin B1 fails to accumulate in the nucleus and could be readily detected at the centrosome in response to DNA damage. Therefore, in normal cells, p21 exerts a dual role in mediating DNA damage-induced cell cycle arrest and exit before mitosis. In addition to blocking pRb phosphorylation, p21 directly prevents mitosis by inactivating and maintaining the inactive state of mitotic cyclin-Cdk complexes. This, with subsequent degradation of mitotic cyclins, further contributes to the establishment of a permanent G2 arrest.

scholarly journals Nuclear localization of the ubiquitin-activating enzyme, E1, is cell-cycle-dependent

1994 ◽  
Vol 300 (3) ◽  
pp. 701-708 ◽  
Author(s):  
S J Grenfell ◽  
J S Trausch-Azar ◽  
P M Handley-Gearhart ◽  
A Ciechanover ◽  
A L Schwartz
Keyword(s):  
Cell Cycle ◽  
Subcellular Localization ◽  
Initial Step ◽  
Immunoblot Analysis ◽  
Subcellular Fractionation ◽  
Cell Extract ◽  
Cell Fractionation ◽  
Differential Distribution ◽  
Cycle Dependent ◽  
Substrate Proteins

The mechanisms that regulate ubiquitin-mediated degradation of proteins such as the mitotic cyclins at defined stages of the cell cycle are poorly understood. The initial step in the conjugation of ubiquitin to substrate proteins involves the activation of ubiquitin by the ubiquitin-activating enzyme, E1. Previously we have described the subcellular localization of this enzyme to both nuclear and cytoplasmic compartments. In the present study, we have used the 1C5 anti-E1 monoclonal antibody in immunofluorescent-microscopy and subcellular-fractionation techniques to examine the distribution of E1 during the HeLa cell cycle. E1 is both cytoskeletal and nuclear during the G1-phase. As the cells progress into S-phase, E1 is exclusively cytoskeletal and has a perinuclear distribution. During G2-phase, E1 reappears in the nucleus before breakdown of the nuclear envelope. In mitotic cells, E1 localizes to both the mitotic spindle and the cytosol, but is absent from the chromosomes. Immunoblot analysis reveals multiple forms of E1 in HeLa whole cell extract. This heterogeneity is not a result of polyubiquitination and may represent inactive pools of E1. Only the characteristic E1 doublet is able to activate ubiquitin. Cell-fractionation studies reveal a differential distribution of specific E1 isoforms throughout the cell cycle. Therefore we propose that the subcellular localization of E1 may play a role in regulating cell-cycle-dependent conjugation of ubiquitin to target proteins.

scholarly journals Investigating the Central Dogma of Molecular Biology in the Context of Nuclear Architecture and Cell Cycle

2019 ◽  
Author(s):  
Shivnarayan Dhuppar ◽  
Aprotim Mazumder
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Single Molecule ◽  
Mammalian Cells ◽  
Nuclear Architecture ◽  
Nuclear Lamina ◽  
Gene Copy ◽  
A Cell ◽  
Cycle Dependent

AbstractNuclear architecture is the organization of the genome within a cell nucleus with respect to different nuclear landmarks such as nuclear lamina, matrix or nucleoli. Lately it has emerged as a major regulator of gene expression in mammalian cells. The studies connecting nuclear architecture with gene expression are largely population-averaged and do not report on the heterogeneity in genome organization or in gene expression within a population. In this report we present a method for combining 3D DNA Fluorescence in situ Hybridization (FISH) with single molecule RNA FISH (smFISH) and immunofluorescence to study nuclear architecture-dependent gene regulation on a cell-by-cell basis. We further combine it with an imaging-based cell cycle staging to correlate nuclear architecture with gene expression across the cell cycle. We present this in the context of Cyclin A2 (CCNA2) gene for its known cell cycle-dependent expression. We show that, across the cell cycle, the expression of a CCNA2 gene copy is stochastic and depends neither on its sub-nuclear position—which usually lies close to nuclear lamina—nor on the expression from the other copies.

scholarly journals Cell cycle-dependent phosphorylation of the 77 kDa echinoderm microtubule-associated protein (EMAP) in vivo and association with the p34cdc2 kinase

1996 ◽  
Vol 109 (12) ◽  
pp. 2885-2893 ◽  
Author(s):  
E. Brisch ◽  
M.A. Daggett ◽  
K.A. Suprenant
Keyword(s):  
Cell Cycle ◽  
Sea Urchin ◽  
Time Course ◽  
Mitotic Apparatus ◽  
Sea Urchin Eggs ◽  
Spindle Poles ◽  
A Cell ◽  
Cycle Dependent ◽  
Phosphopeptide Mapping

The most abundant microtubule-associated protein in sea urchin eggs and embryos is the 77 kDa echinoderm microtubule-associated protein (EMAP). EMAP localizes to the mitotic spindle as well as the interphase microtubule array and is a likely target for a cell cycle-activated kinase. To determine if EMAP is phosphorylated in vivo, sea urchin eggs and embryos were metabolically labeled with 32PO4 and a monospecific antiserum was used to immunoprecipitate EMAP from 32P-labeled eggs and embryos. In this study, we demonstrate that the 77 kDa EMAP is phosphorylated in vivo by two distinct mechanisms. In the unfertilized egg, EMAP is constitutively phosphorylated on at least five serine residues. During the first cleavage division following fertilization, EMAP is phosphorylated with a cell cycle-dependent time course. As the embryo enters mitosis, EMAP phosphorylation increases, and as the embryo exits mitosis, phosphorylation decreases. During mitosis, EMAP is phosphorylated on 10 serine residues and two-dimensional phosphopeptide mapping reveals a mitosis-specific site of phosphorylation. At all stages of the cell cycle, a 33 kDa polypeptide copurifies with the 77 kDa EMAP, regardless of phosphorylation state. Antibodies against the cdc2 kinase were used to demonstrate that the 33 kDa polypeptide is the p34cdc2 kinase. The p34cdc2 kinase copurifies with the mitotic apparatus and immunostaining indicates that the p34cdc2 kinase is concentrated at the spindle poles. Models for the interaction of the p34cdc2 kinase and the 77 kDa EMAP are presented.

scholarly journals Cell Cycle-Dependent Switch of TopBP1 Functions by Cdk2 and Akt

2020 ◽  
Vol 40 (8) ◽  
Author(s):  
Kang Liu ◽  
Joshua D. Graves ◽  
Yu-Ju Lee ◽  
Fang-Tsyr Lin ◽  
Weei-Chin Lin
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Cancer Cells ◽  
Cyclin A ◽  
Replication Initiation ◽  
Dna Replication Initiation ◽  
Cycle Dependent

ABSTRACT Cdk2-dependent TopBP1-treslin interaction is critical for DNA replication initiation. However, it remains unclear how this association is terminated after replication initiation is finished. Here, we demonstrate that phosphorylation of TopBP1 by Akt coincides with cyclin A activation during S and G2 phases and switches the TopBP1-interacting partner from treslin to E2F1, which results in the termination of replication initiation. Premature activation of Akt in G1 phase causes an early switch and inhibits DNA replication. TopBP1 is often overexpressed in cancer and can bypass control by Cdk2 to interact with treslin, leading to enhanced DNA replication. Consistent with this notion, reducing the levels of TopBP1 in cancer cells restores sensitivity to a Cdk2 inhibitor. Together, our study links Cdk2 and Akt pathways to the control of DNA replication through the regulation of TopBP1-treslin interaction. These data also suggest an important role for TopBP1 in driving abnormal DNA replication in cancer.

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