p21WAF1/CIP1 Inhibits Cell Cycle Progression but Not G2/M-Phase Transition Following Methylmercury Exposure

Cdc25 phosphatases play key roles in cell cycle progression by activating cyclin-dependent kinases. In human cells, cdc25 proteins are encoded by a multigene family, consisting of cdc25A, cdc25B and cdc25C. While cdc25A plays a crucial role at the G1/S phase transition, cdc25C is involved in the dephosphorylation and activation of the mitotic kinase, cdc2/cyclinB. In addition, cdc25C itself is regulated by cdc2/cyclinB which then creates a positive feedback loop that controls entry into mitosis. In this study we show that the activity of cdc25B appears during late S phase and peaks during G2 phase. Both in vitro and in vivo cdc25B is activated through phosphorylation during S-phase. Using a cell duplication, microinjection assay we show that ablation of cdc25B function by specific antibodies blocks cell cycle progression in Hs68 cells by inhibition of entry into mitosis. Cdc25B function neither plays a role in later stages of mitosis nor for the inititation of DNA replication. These results indicate that cdc25B is a mitotic regulator that might act as a ‘starter phosphatase’ to initiate the positive feedback loop at the entry into M phase.

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Cdk1-Mediated Phosphorylation of Human ATF7 at Thr-51 and Thr-53 Promotes Cell-Cycle Progression into M Phase

PLoS ONE ◽

10.1371/journal.pone.0116048 ◽

2014 ◽

Vol 9 (12) ◽

pp. e116048 ◽

Cited By ~ 11

Author(s):

Hitomi Hasegawa ◽

Kenichi Ishibashi ◽

Shoichi Kubota ◽

Chihiro Yamaguchi ◽

Ryuzaburo Yuki ◽

...

Keyword(s):

Cell Cycle ◽

Cell Cycle Progression ◽

Cycle Progression ◽

M Phase

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Regulation of Cell Cycle Progression by Growth Factor-Induced Cell Signaling

Cells ◽

10.3390/cells10123327 ◽

2021 ◽

Vol 10 (12) ◽

pp. 3327

Author(s):

Zhixiang Wang

Keyword(s):

Cell Cycle ◽

Growth Factor ◽

Signaling Pathways ◽

Tyrosine Kinases ◽

Cell Cycle Progression ◽

Phase Cell ◽

Growth Factor Signaling ◽

Cycle Progression ◽

M Phase

The cell cycle is the series of events that take place in a cell, which drives it to divide and produce two new daughter cells. The typical cell cycle in eukaryotes is composed of the following phases: G1, S, G2, and M phase. Cell cycle progression is mediated by cyclin-dependent kinases (Cdks) and their regulatory cyclin subunits. However, the driving force of cell cycle progression is growth factor-initiated signaling pathways that control the activity of various Cdk–cyclin complexes. While the mechanism underlying the role of growth factor signaling in G1 phase of cell cycle progression has been largely revealed due to early extensive research, little is known regarding the function and mechanism of growth factor signaling in regulating other phases of the cell cycle, including S, G2, and M phase. In this review, we briefly discuss the process of cell cycle progression through various phases, and we focus on the role of signaling pathways activated by growth factors and their receptor (mostly receptor tyrosine kinases) in regulating cell cycle progression through various phases.

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Akt/Protein Kinase B-Dependent Phosphorylation and Inactivation of WEE1Hu Promote Cell Cycle Progression at G2/M Transition

Molecular and Cellular Biology ◽

10.1128/mcb.25.13.5725-5737.2005 ◽

2005 ◽

Vol 25 (13) ◽

pp. 5725-5737 ◽

Cited By ~ 97

Author(s):

Kazuhiro Katayama ◽

Naoya Fujita ◽

Takashi Tsuruo

Keyword(s):

Cell Cycle ◽

Cell Cycle Progression ◽

Kinase Inhibitor ◽

Phosphorylation Site ◽

Cytoplasmic Localization ◽

M Cell ◽

Serine Threonine Kinase ◽

Cycle Progression ◽

M Phase ◽

Promote Cell Cycle Progression

ABSTRACT The serine/threonine kinase Akt is known to promote cell growth by regulating the cell cycle in G1 phase through activation of cyclin/Cdk kinases and inactivation of Cdk inhibitors. However, how the G2/M phase is regulated by Akt remains unclear. Here, we show that Akt counteracts the function of WEE1Hu. Inactivation of Akt by chemotherapeutic drugs or the phosphatidylinositide-3-OH kinase inhibitor LY294002 induced G2/M arrest together with the inhibitory phosphorylation of Cdc2. Because the increased Cdc2 phosphorylation was completely suppressed by wee1hu gene silencing, WEE1Hu was associated with G2/M arrest induced by Akt inactivation. Further analyses revealed that Akt directly bound to and phosphorylated WEE1Hu during the S to G2 phase. Serine-642 was identified as an Akt-dependent phosphorylation site. WEE1Hu kinase activity was not affected by serine-642 phosphorylation. We revealed that serine-642 phosphorylation promoted cytoplasmic localization of WEE1Hu. The nuclear-to-cytoplasmic translocation was mediated by phosphorylation-dependent WEE1Hu binding to 14-3-3θ but not 14-3-3β or -σ. These results indicate that Akt promotes G2/M cell cycle progression by inducing phosphorylation-dependent 14-3-3θ binding and cytoplasmic localization of WEE1Hu.

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Cell Cycle-Dependence of Autophagic Activity and Inhibition of Autophagosome Formation at M Phase in Tobacco BY-2 Cells

International Journal of Molecular Sciences ◽

10.3390/ijms21239166 ◽

2020 ◽

Vol 21 (23) ◽

pp. 9166

Author(s):

Shigeru Hanamata ◽

Takamitsu Kurusu ◽

Kazuyuki Kuchitsu

Keyword(s):

Cell Cycle ◽

Cell Cycle Progression ◽

Plant Cells ◽

Regulatory Mechanisms ◽

Cdk Inhibitor ◽

Autophagosome Formation ◽

Cycle Progression ◽

M Phase ◽

Cell Cycle Dependence ◽

Cycle Dependence

Autophagy is ubiquitous in eukaryotic cells and plays an essential role in stress adaptation and development by recycling nutrients and maintaining cellular homeostasis. However, the dynamics and regulatory mechanisms of autophagosome formation during the cell cycle in plant cells remain poorly elucidated. We here analyzed the number of autophagosomes during cell cycle progression in synchronized tobacco BY-2 cells expressing YFP-NtATG8a as a marker for the autophagosomes. Autophagosomes were abundant in the G2 and G1 phases of interphase, though they were much less abundant in the M and S phases. Autophagosomes drastically decreased during the G2/M transition, and the CDK inhibitor roscovitine inhibited the G2/M transition and the decrease in autophagosomes. Autophagosomes were rapidly increased by a proteasome inhibitor, MG-132. MG-132-induced autophagosome formation was also markedly lower in the M phases than during interphase. These results indicate that the activity of autophagosome formation is differently regulated at each cell cycle stage, which is strongly suppressed during mitosis.

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Regulatory effect of thromboxane A2 on proliferation of vascular smooth muscle cells from rats

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1992.263.5.h1331 ◽

1992 ◽

Vol 263 (5) ◽

pp. H1331-H1338 ◽

Cited By ~ 3

Author(s):

T. Nagata ◽

Y. Uehara ◽

A. Numabe ◽

T. Ishimitsu ◽

N. Hirawa ◽

...

Keyword(s):

Cell Cycle ◽

Protein Synthesis ◽

Smooth Muscle ◽

Smooth Muscle Cells ◽

Vascular Smooth Muscle Cells ◽

Cell Cycle Progression ◽

Thromboxane A2 ◽

Cycle Progression ◽

M Phase ◽

Rapid Transition

We investigated the regulatory effects of the vasoconstrictor thromboxane A2 on the proliferation of vascular smooth muscle cells (VSMC) from Wistar-Kyoto rats using 9,11-epithio-11,12-methano-thromboxane A2 (STA2), a stable analogue of thromboxane A2. STA2 dose dependently increased incorporation of [3H]thymidine into DNA in randomly cycling VSMC and significantly shortened the doubling time. Cell cycle analysis revealed that the increased cell cycle progression was primarily due to a rapid transition from the DNA synthetic (S) to the G2/mitotic (M) phase. Moreover, STA2 enhanced protein synthesis in VSMC during the G2/M phase, whereas the protein synthesis was unaffected in the G0/G1 period. In fact, STA2 prompted the cells in G2/M phase to synthesize actin, a major cytoskeleton protein. Conversely, inhibition of protein synthesis by puromycin retarded the transition from S to G2/M. In addition, depolymerization of the actin molecules by cytochalasin D offset the quick progression to the G2/M phase by STA2. These data indicate that thromboxane A2 stimulates the cell cycle progression in VSMC primarily through a rapid transition from S to G2/M. This enhanced progression is attributable partly to a rapid buildup of the cytoskeleton proteins during the G2/M period.

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The Fluctuation of Telomere Repeat Binding Factor 1 during Cell Cycle and Its Localization in Telomerase-Positive and Negative Cells.

Blood ◽

10.1182/blood.v104.11.4326.4326 ◽

2004 ◽

Vol 104 (11) ◽

pp. 4326-4326

Author(s):

Jianping Lan ◽

He Huang ◽

Yuanyuan Zhu ◽

Jie Sun

Keyword(s):

Cell Cycle ◽

Telomere Length ◽

Hela Cells ◽

Cell Cycle Progression ◽

Promyelocytic Leukemia ◽

Final Concentration ◽

Cycle Progression ◽

Telomere Repeat ◽

Binding Factor ◽

M Phase

Abstract Telomere is a nucleoprotein complex which caps the extreme ends of eukaryotic chromosomes. In human, telomere is composed of a tandem repeat array of TTAGGG hexanucleotide and bound to a set of specific proteins. These proteins function to maintain the integrity of chromosomes and genomic stability. Among these proteins, telomere repeat binding factor 1(TRF1) is the first telomere binding protein which was isolated by DNA affinity chromatography in 1995. TRF1 serves as a negative regulator of telomere length since TRF1 overexpression would elicit the shortening of telomere length in telomerase-positive cells. Meanwhile, overexpression of TRF1 would also induce the entry into mitosis and increase mitotic cells. These observation indicated TRF1 might participate in cell cycle regulation. However, the underlying mechanism in which TRF1 regulates the cell cycle and the endogenous level of TRF1 were not well-documented during cell cycle progression. To address these questions, we arrested HeLa cells at different phases by a combination of thymidine(5mM at final concentration) and nocodazole(20mM at final concentration) and detected the TRF1 levels by semi-quantitive Western Blotting assay. Cell cycle was verified by flow cytometry. Our results showed TRF1 level fluctuated coincided with cell cycle progression which reached the zenith at the M phase and went down to the nadir at G1/S point. Densitometry analysis demonstrated that the level of TRF1 at M phase was 3.9 times more than that at G1/S point(n=3, p<0.01). These results suggested that TRF1 might be essential for proper cell cycle progression and it was likely to take part in regulation of cell cycle chechpoint. TRF1 is also expressed in telomerase-negative cells. To further discriminate the different functions of TRF1 and decipher its protein-protein interaction network in telomerase-positive and negative cells, full-length TRF1 cDNA was amplified by PCR and subsequently subcloned into pEGFP-C2 vector to express TRF1 tagged by enhanced green fluorescent protein. This construct was then transiently transfected into telomerase-negative cells(WI38-2RA) and telomerase-positive cells(HeLa). Immunoflourescent staining was employed to check the localization of TRF1 in these two kinds of cells. Although in both cells, TRF1 was distributed in a speckled pattern in the nuclei, TRF1 did exclusively colocalize with promyelocytic leukemia(PML) nuclear body in WI38-2RA cells but not in HeLa cells. PML fused with RARα due to chromosome15,17 translocation which led to disassembly of PML nucleur body in acute promyelocytic leukemia. These preliminary results suggested that TRF1 might have the different regulating mechanism and interacting network.

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Effect of the Serum Inhibited Gene (Si1) on Autophagy and Apoptosis in MCF-7 Breast Cancer Cells

Cellular Physiology and Biochemistry ◽

10.1159/000475644 ◽

2017 ◽

Vol 41 (6) ◽

pp. 2268-2278 ◽

Cited By ~ 4

Author(s):

Yu Li ◽

Yong Cui ◽

Wenxue Wang ◽

Mingxing Ma ◽

Meizhang Li ◽

...

Keyword(s):

Cell Cycle ◽

Tumor Cells ◽

Western Blotting ◽

Cell Cycle Progression ◽

Hoechst 33258 ◽

Cycle Progression ◽

Important Relationship ◽

M Phase ◽

Inhibit Cell Proliferation ◽

Mcf 7

Background/Aims: The serum inhibited gene (Si1) was named according to its inhibited expression in response to serum exposure. Si1 has an important relationship with tumors. Autophagy and apoptosis are two types of cell death. However, there are few studies regarding the association between Si1 and autophagy, or apoptosis in tumors. In this, we investigated the effect of Si1 on the proliferation and cell cycle progression of MCF-7 cells and its influence on autophagy and apoptosis in MCF-7 cells. Methods: To investigate these functions of Si1 in tumor cells, we firstly constructed a pEGFP-Si1 overexpression vector and a pSilencer-Si1 interference vector, and we subsequently tested the proliferation and cell cycle progression of MCF-7 cells using the MTT assay and flow cytometry, and we then detected autophagy by western blotting and MDC (Monodansylcadaverine) staining as well as apoptosis by western blotting and Hoechst 33258 staining. Results: We found that the Si1 gene can significantly inhibit the viability of MCF-7 cells and arrest the cell cycle at the G2/M phase. Si1 can induce autophagy through upregulation of LC3-II and Beclin1, it can induce apoptosis through cleavage of PARP in MCF-7 cells. Conclusion: Altogether, our study indicated that Si1 can inhibit cell proliferation of MCF-7, and also induces autophagy and apoptosis. This study firstly investigated the effect of Si1 on autophagy and apoptosis in MCF-7 cells. Moreover, it also improves the current understanding of the mechanisms related to the effect of Si1 on tumor cells and also provides a foundation for gene-targeted therapy.

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Sfh1p, a component of a novel chromatin-remodeling complex, is required for cell cycle progression.

Molecular and Cellular Biology ◽

10.1128/mcb.17.6.3323 ◽

1997 ◽

Vol 17 (6) ◽

pp. 3323-3334 ◽

Cited By ~ 78

Author(s):

Y Cao ◽

B R Cairns ◽

R D Kornberg ◽

B C Laurent

Keyword(s):

Cell Cycle ◽

Chromatin Remodeling ◽

Cell Cycle Progression ◽

Normal Function ◽

Temperature Sensitive ◽

Cycle Progression ◽

Conserved Domain ◽

Chromatin Remodeling Complex ◽

Evolutionarily Conserved ◽

M Phase

Several eukaryotic multiprotein complexes, including the Saccharomyces cerevisiae Snf/Swi complex, remodel chromatin for transcription. In contrast to the Snf/Swi proteins, Sfh1p, a new Snf5p paralog, is essential for viability. The evolutionarily conserved domain of Sfh1p is sufficient for normal function, and Sfh1p interacts functionally and physically with an essential Snf2p paralog in a novel nucleosome-restructuring complex called RSC (for remodels the structure of chromatin). A temperature-sensitive sfh1 allele arrests cells in the G2/M phase of the cell cycle, and the Sfh1 protein is specifically phosphorylated in the G1 phase. Together, these results demonstrate a link between chromatin remodeling and progression through the cell division cycle, providing genetic clues to possible targets for RSC function.

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BCL-2 Is Phosphorylated and Inactivated by an ASK1/Jun N-Terminal Protein Kinase Pathway Normally Activated at G2/M

Molecular and Cellular Biology ◽

10.1128/mcb.19.12.8469 ◽

1999 ◽

Vol 19 (12) ◽

pp. 8469-8478 ◽

Cited By ~ 706

Author(s):

Kazuhito Yamamoto ◽

Hidenori Ichijo ◽

Stanley J. Korsmeyer

Keyword(s):

Cell Cycle ◽

Protein Kinase ◽

Cell Cycle Progression ◽

Peptide Mapping ◽

Dominant Negative ◽

Terminal Protein ◽

Cycle Progression ◽

M Phase ◽

Death Signals

ABSTRACT Multiple signal transduction pathways are capable of modifying BCL-2 family members to reset susceptibility to apoptosis. We used two-dimensional peptide mapping and sequencing to identify three residues (Ser70, Ser87, and Thr69) within the unstructured loop of BCL-2 that were phosphorylated in response to microtubule-damaging agents, which also arrest cells at G2/M. Changing these sites to alanine conferred more antiapoptotic activity on BCL-2 following physiologic death signals as well as paclitaxel, indicating that phosphorylation is inactivating. An examination of cycling cells enriched by elutriation for distinct phases of the cell cycle revealed that BCL-2 was phosphorylated at the G2/M phase of the cell cycle. G2/M-phase cells proved more susceptible to death signals, and phosphorylation of BCL-2 appeared to be responsible, as a Ser70Ala substitution restored resistance to apoptosis. We noted that ASK1 and JNK1 were normally activated at G2/M phase, and JNK was capable of phosphorylating BCL-2. Expression of a series of wild-type and dominant-negative kinases indicated an ASK1/Jun N-terminal protein kinase 1 (JNK1) pathway phosphorylated BCL-2 in vivo. Moreover, the combination of dominant negative ASK1, (dnASK1), dnMKK7, and dnJNK1 inhibited paclitaxel-induced BCL-2 phosphorylation. Thus, stress response kinases phosphorylate BCL-2 during cell cycle progression as a normal physiologic process to inactivate BCL-2 at G2/M.

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