Heat shock results in cell cycle delay and synchronisation of mitotic domains in cellularised Drosophila melanogaster embryos

Cells of Drosophila embryos that are subjected to a 37 degrees C temperature shock whilst undergoing the S-phase of cell cycle 14 arrest with their microtubules in an interphase-like state, and with nuclei showing unusual chromatin condensation. They do not recover from this state within a 30 minute period even though extensive gastrulation movements can occur. Cells of embryos heat shocked in G2-phase are delayed in interphase with high levels of cyclins A and B. Within ten minutes recovery from heat shock, cells enter mitosis throughout the embryo. The degradation of the mitotic cyclins A and B in these synchronised mitotic domains does not follow the normal timing, but is delayed. These findings point to a need for caution when interpreting experiments that use the heat shock promoter to study the expression of cell cycle control genes in Drosophila.

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Regulation of Cell Cycle Progression by Swe1p and Hog1p Following Hypertonic Stress

Molecular Biology of the Cell ◽

10.1091/mbc.12.1.53 ◽

2001 ◽

Vol 12 (1) ◽

pp. 53-62 ◽

Cited By ~ 74

Author(s):

Matthew R. Alexander ◽

Mike Tyers ◽

Mireille Perret ◽

B. Maureen Craig ◽

Karen S. Fang ◽

...

Keyword(s):

Cell Cycle ◽

Kinase Activity ◽

Phosphorylation Site ◽

S Phase ◽

Mitogen Activated Protein Kinase ◽

Yeast Cells ◽

Hypertonic Stress ◽

Cell Cycle Delay ◽

G2 Phase ◽

Morphogenesis Checkpoint

Exposure of yeast cells to an increase in external osmolarity induces a temporary growth arrest. Recovery from this stress is mediated by the accumulation of intracellular glycerol and the transcription of several stress response genes. Increased external osmolarity causes a transient accumulation of 1N and 2N cells and a concomitant depletion of S phase cells. Hypertonic stress triggers a cell cycle delay in G2 phase cells that appears distinct from the morphogenesis checkpoint, which operates in early S phase cells. Hypertonic stress causes a decrease in CLB2 mRNA, phosphorylation of Cdc28p, and inhibition of Clb2p-Cdc28p kinase activity, whereas Clb2 protein levels are unaffected. Like the morphogenesis checkpoint, the osmotic stress-induced G2 delay is dependent upon the kinase Swe1p, but is not tightly correlated with inhibition of Clb2p-Cdc28p kinase activity. Thus, deletion ofSWE1 does not prevent the hypertonic stress-induced inhibition of Clb2p-Cdc28p kinase activity. Mutation of the Swe1p phosphorylation site on Cdc28p (Y19) does not fully eliminate the Swe1p-dependent cell cycle delay, suggesting that Swe1p may have functions independent of Cdc28p phosphorylation. Conversely, deletion of the mitogen-activated protein kinase HOG1 does prevent Clb2p-Cdc28p inhibition by hypertonic stress, but does not block Cdc28p phosphorylation or alleviate the cell cycle delay. However, Hog1p does contribute to proper nuclear segregation after hypertonic stress in cells that lack Swe1p. These results suggest a hypertonic stress-induced cell cycle delay in G2 phase that is mediated in a novel way by Swe1p in cooperation with Hog1p.

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Mutational analyses of fs(1)Ya, an essential, developmentally regulated, nuclear envelope protein in Drosophila.

Genetics ◽

10.1093/genetics/141.4.1473 ◽

1995 ◽

Vol 141 (4) ◽

pp. 1473-1481 ◽

Cited By ~ 1

Author(s):

J Liu ◽

K Song ◽

M F Wolfner

Keyword(s):

Cell Cycle ◽

Embryonic Development ◽

Nuclear Envelope ◽

Envelope Protein ◽

Chromatin Condensation ◽

Cell Cycle Control ◽

Nuclear Lamina ◽

Mitotic Division ◽

Developmentally Regulated ◽

Egg Maturation

Abstract The fs(1)Ya protein (YA) is an essential, maternally encoded, nuclear lamina protein that is under both developmental and cell cycle control. A strong Ya mutation results in early arrest of embryos. To define the function of YA in the nuclear envelope during early embryonic development, we characterized the phenotypes of four Ya mutants alleles and determined their molecular lesions. Ya mutant embryos arrest with abnormal nuclear envelopes prior to the first mitotic division; a proportion of embryos from two leaky Ya mutants proceed beyond this but arrest after several abnormal divisions. Ya unfertilized eggs contain nuclei of different sizes and condensation states, apparently due to abnormal fusion of the meiotic products immediately after meiosis. Lamin is localized at the periphery of the uncondensed nuclei in these eggs. These results suggest that YA function is required during and after egg maturation to facilitate proper chromatin condensation, rather than to allow a lamin-containing nuclear envelope to form. Two leaky Ya alleles that partially complement have lesions at opposite ends of the YA protein, suggesting that the N- and C-termini are important for YA function and that YA might interact with itself either directly or indirectly.

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The Schizosaccharomyces pombe hus5 gene encodes a ubiquitin conjugating enzyme required for normal mitosis

Journal of Cell Science ◽

10.1242/jcs.108.2.475 ◽

1995 ◽

Vol 108 (2) ◽

pp. 475-486 ◽

Cited By ~ 9

Author(s):

F. al-Khodairy ◽

T. Enoch ◽

I.M. Hagan ◽

A.M. Carr

Keyword(s):

Cell Cycle ◽

Dna Synthesis ◽

Schizosaccharomyces Pombe ◽

Cell Cycle Control ◽

S Phase ◽

Temperature Sensitive ◽

Checkpoint Control ◽

Ubiquitin Conjugating Enzyme ◽

Efficient Recovery ◽

Mediate Cell

Normal eukaryotic cells do not enter mitosis unless DNA is fully replicated and repaired. Controls called ‘checkpoints’, mediate cell cycle arrest in response to unreplicated or damaged DNA. Two independent Schizosaccharomyces pombe mutant screens, both of which aimed to isolate new elements involved in checkpoint controls, have identified alleles of the hus5+ gene that are abnormally sensitive to both inhibitors of DNA synthesis and to ionizing radiation. We have cloned and sequenced the hus5+ gene. It is a novel member of the E2 family of ubiquitin conjugating enzymes (UBCs). To understand the role of hus5+ in cell cycle control we have characterized the phenotypes of the hus5 mutants and the hus5 gene disruption. We find that, whilst the mutants are sensitive to inhibitors of DNA synthesis and to irradiation, this is not due to an inability to undergo mitotic arrest. Thus, the hus5+ gene product is not directly involved in checkpoint control. However, in common with a large class of previously characterized checkpoint genes, it is required for efficient recovery from DNA damage or S-phase arrest and manifests a rapid death phenotype in combination with a temperature sensitive S phase and late S/G2 phase cdc mutants. In addition, hus5 deletion mutants are severely impaired in growth and exhibit high levels of abortive mitoses, suggesting a role for hus5+ in chromosome segregation. We conclude that this novel UBC enzyme plays multiple roles and is virtually essential for cell proliferation.

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Excision and replication of extrachromosomal DNA of pea (Pisum sativum)

Molecular and Cellular Biology ◽

10.1128/mcb.3.2.172-181.1983 ◽

1983 ◽

Vol 3 (2) ◽

pp. 172-181

Author(s):

J Van't Hof ◽

C A Bjerknes ◽

N C Delihas

Keyword(s):

Cell Cycle ◽

Pisum Sativum ◽

S Phase ◽

Velocity Sedimentation ◽

Extrachromosomal Dna ◽

Chromosomal Dna ◽

Root Tips ◽

Dividing Cells ◽

G2 Phase ◽

Pea Roots

Experiments with cultured pea roots were conducted to determine (i) whether extrachromosomal DNA was produced by cells in the late S phase or in the G2 phase of the cell cycle, (ii) whether the maturation of nascent DNA replicated by these cells achieved chromosomal size, (iii) when extrachromosomal DNA was removed from the chromosomal duplex, and (iv) the replication of nascent chains by the extrachromosomal DNA after its release from the chromosomal duplex. Autoradiography and cytophotometry of cells of carbohydrate-starved root tips revealed that extrachromosomal DNA was produced by a small fraction of cells accumulated in the late S phase after they had replicated about 80% of their DNA. Velocity sedimentation of nascent chromosomal DNA in alkaline sucrose gradients indicated that the DNA of cells in the late S phase failed to achieve chromosomal size. After reaching sizes of 70 X 10(6) to 140 X 10(6) daltons, some of the nascent chromosomal molecules were broken, presumably releasing extrachromosomal DNA several hours later. Sedimentation of selectively extracted extrachromosomal DNA either from dividing cells or from those in the late S phase showed that it replicated two nascent chains, one of 3 X 10(6) daltons and another of 7 X 10(6) daltons. Larger molecules of extrachromosomal DNA were detectable after cells were labeled for 24 h. These two observations were compatible with the idea that the extrachromosomal DNA was first replicated as an integral part of the chromosomal duplex, was cut from the duplex, and then, once free of the chromosome, replicated two smaller chains of 3 X 10(6) and 7 X 10(6) daltons.

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Enhancement of DNA-mediated gene transfer by high-Mr carrier DNA in synchronized CV-1 cells

Biochemical Journal ◽

10.1042/bj2250529 ◽

1985 ◽

Vol 225 (2) ◽

pp. 529-533 ◽

Cited By ~ 8

Author(s):

A J Strain ◽

W A H Wallace ◽

A H Wyllie

Keyword(s):

Cell Cycle ◽

Gene Transfer ◽

Transfection Efficiency ◽

Simian Virus 40 ◽

Simian Virus ◽

S Phase ◽

Sv40 Virus ◽

G2 Phase ◽

Cycle Dependent ◽

Sv40 Dna

Synchronized CV-1 cells were transfected with SV40 (simian virus 40) DNA-calcium phosphate co-precipitates. In the presence of carrier DNA, the transfection efficiency of SV40 DNA was decreased 5-fold in S-phase cells and was increased 4-fold in preparations of mitotically enriched cells as compared with asynchronous controls. No difference was observed when carrier DNA was omitted, when cells had progressed through S-phase and into G2-phase, or when the infectivity of cells to intact SV40 virus was tested. These results highlight the importance of cell-cycle-dependent factors on DNA-mediated gene transfer.

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Role of Phospholipid Metabolites in the Cell Cycle Delay Caused by Epidermal Growth Factor at the Transition from G2-Phase to Mitosis in A431 Cells

Eicosanoids and Other Bioactive Lipids in Cancer, Inflammation and Radiation Injury ◽

10.1007/978-1-4615-3520-1_105 ◽

1993 ◽

pp. 537-540

Author(s):

M. Kaszkin ◽

V. Kinzel

Keyword(s):

Cell Cycle ◽

Growth Factor ◽

Epidermal Growth Factor ◽

A431 Cells ◽

Cell Cycle Delay ◽

Epidermal Growth ◽

G2 Phase

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Cell cycle arrest of cdc mutants and specificity of the RAD9 checkpoint.

Genetics ◽

10.1093/genetics/134.1.63 ◽

1993 ◽

Vol 134 (1) ◽

pp. 63-80 ◽

Cited By ~ 9

Author(s):

T A Weinert ◽

L H Hartwell

Keyword(s):

Cell Cycle ◽

Cell Division ◽

Dna Replication ◽

Cell Cycle Control ◽

Dna Lesions ◽

Temperature Sensitive ◽

Restrictive Temperature ◽

A Cell ◽

G2 Phase ◽

Rad Mutants

Abstract In eucaryotes a cell cycle control called a checkpoint ensures that mitosis occurs only after chromosomes are completely replicated and any damage is repaired. The function of this checkpoint in budding yeast requires the RAD9 gene. Here we examine the role of the RAD9 gene in the arrest of the 12 cell division cycle (cdc) mutants, temperature-sensitive lethal mutants that arrest in specific phases of the cell cycle at a restrictive temperature. We found that in four cdc mutants the cdc rad9 cells failed to arrest after a shift to the restrictive temperature, rather they continued cell division and died rapidly, whereas the cdc RAD cells arrested and remained viable. The cell cycle and genetic phenotypes of the 12 cdc RAD mutants indicate the function of the RAD9 checkpoint is phase-specific and signal-specific. First, the four cdc RAD mutants that required RAD9 each arrested in the late S/G2 phase after a shift to the restrictive temperature when DNA replication was complete or nearly complete, and second, each leaves DNA lesions when the CDC gene product is limiting for cell division. Three of the four CDC genes are known to encode DNA replication enzymes. We found that the RAD17 gene is also essential for the function of the RAD9 checkpoint because it is required for phase-specific arrest of the same four cdc mutants. We also show that both X- or UV-irradiated cells require the RAD9 and RAD17 genes for delay in the G2 phase. Together, these results indicate that the RAD9 checkpoint is apparently activated only by DNA lesions and arrests cell division only in the late S/G2 phase.

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Cubic Membranes Formation in Synchronized Human Hepatocellular Carcinoma Cells Reveals a Possible Role as a Structural Antioxidant Defense System in Cell Cycle Progression

Frontiers in Cell and Developmental Biology ◽

10.3389/fcell.2020.617406 ◽

2020 ◽

Vol 8 ◽

Author(s):

Deqin Kong ◽

Rui Liu ◽

Jiangzheng Liu ◽

Qingbiao Zhou ◽

Jiaxin Zhang ◽

...

Keyword(s):

Hepatocellular Carcinoma ◽

Cell Cycle ◽

Cell Cycle Progression ◽

S Phase ◽

Carcinoma Cells ◽

Human Hepatocellular Carcinoma ◽

Cycle Progression ◽

Hepatocellular Carcinoma Cells ◽

G2 Phase ◽

Human Hepatocellular Carcinoma Cells

Cubic membranes (CMs) represent unique biological membrane structures with highly curved three-dimensional periodic minimal surfaces, which have been observed in a wide range of cell types and organelles under various stress conditions (e. g., starvation, virus-infection, and oxidation). However, there are few reports on the biological roles of CMs, especially their roles in cell cycle. Hence, we established a stable cell population of human hepatocellular carcinoma cells (HepG2) of 100% S phase by thymidine treatment, and determined certain parameters in G2 phase released from S phase. Then we found a close relationship between CMs formation and cell cycle, and an increase in reactive oxygen species (ROS) and mitochondrial function. After the synchronization of HepG2 cells were induced, CMs were observed through transmission electron microscope in G2 phase but not in G1, S and M phase. Moreover, the increased ATP production, mitochondrial and intracellular ROS levels were also present in G2 phase, which demonstrated a positive correlation with CMs formation by Pearson correlation analysis. This study suggests that CMs may act as an antioxidant structure in response to mitochondria-derived ROS during G2 phase and thus participate in cell cycle progression.

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Maximal binding levels of an H1 histone gene-specific factor in S-phase correlate with maximal H1 gene transcription.

Molecular and Cellular Biology ◽

10.1128/mcb.8.10.4576 ◽

1988 ◽

Vol 8 (10) ◽

pp. 4576-4578 ◽

Cited By ~ 20

Author(s):

S Dalton ◽

J R Wells

Keyword(s):

Cell Cycle ◽

Nucleic Acids ◽

Gene Transcription ◽

S Phase ◽

Histone Gene ◽

Specific Factor ◽

Synchronized Cells ◽

Phase Regulation ◽

G2 Phase ◽

Binding Component

Levels of trans-acting factor (H1-SF) binding to the histone H1 gene-specific motif (5'-AAACACA-3' [L. S. Coles and J. R. E. Wells, Nucleic Acids Res. 13:585-594, 1985]) increase 12-fold from G1 to S-phase in synchronized cells and decrease again in G2 phase of the cell cycle. Since the H1 element is required for S-phase expression of H1 genes (S. Dalton and J. R. E. Wells, EMBO J. 7:49-56, 1988), it is likely that the increased levels of H1-SF binding component play an important role in S-phase regulation of H1 gene transcription.

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