scholarly journals The APC/CCCS52A2 E3-Ligase Complex targeted PKN1 Protein is a Plant Lineage-Specific Driver of Cell Division

2021 ◽  
Author(s):  
Alex Willems ◽  
Yuanke Liang ◽  
Jefri Heyman ◽  
Thomas Eekhout ◽  
Hilde Van den Daele ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Ectopic Expression ◽  
Preprophase Band ◽  
Cycle Phase ◽  
Cell Phenotype ◽  
Marchantia Polymorpha ◽  
Specific Gene ◽  
Accumulation Pattern ◽  
Rate Limiting

ABSTRACTThe anaphase-promoting complex/cyclosome (APC/C) marks key cell cycle proteins for proteasomal breakdown, thereby ensuring unidirectional progression through the cell cycle. Its target recognition is temporally regulated by activating subunits, one of which is called CELL CYCLE SWITCH 52 A2 (CCS52A2). We sought to expand the knowledge of identified APC/C targets by using the severe growth phenotypes of CCS52A2-deficient Arabidopsis thaliana plants as a readout in a suppressor mutagenesis screen, resulting in the identification of the previously undescribed gene called PIKMIN1 (PKN1). PKN1 deficiency rescues the disorganized root stem cell phenotype of the ccs52a2-1 mutant, whereas an excess of PKN1 inhibits growth of ccs52a2-1 plants, indicating the importance of PKN1 abundance for proper development. Accordingly, the lack of PKN1 in a wild-type background negatively impacts cell division, while its ectopic expression promotes proliferation. PKN1 shows a cell cycle phase-dependent accumulation pattern, localizing to microtubular structures, including the preprophase band, the mitotic spindle, and phragmoplast. PKN1 is conserved throughout the plant kingdom, with its function in cell division being evolutionary conserved in the liverwort Marchantia polymorpha. Our data thus demonstrate that PKN1 represents a novel, plant-specific gene with a rate-limiting role in cell division, which is proteolytically controlled by the CCS52A2-activated APC/C.One-Sentence SummaryPKN1 is a conserved plant-specific protein that is rate-limiting for cell division, likely through its interaction with microtubuli, and is proteolytically controlled by APC/CCCS52A2.

scholarly journals Scheduling Chemotherapy: Catch 22 between Cell Kill and Resistance Evolution

2000 ◽  
Vol 2 (3) ◽  
pp. 215-232 ◽  
Author(s):  
Shea N. Gardner
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Drug Exposure ◽  
Drug Application ◽  
Growth Fraction ◽  
Cycle Phase ◽  
Response Curves ◽  
Division Rate ◽  
Drug Concentrations ◽  
Cns Drugs

Dose response curves show that prolonged drug exposure at a low concentration may kill more cells than short exposures at higher drug concentrations, particularly for cell cycle phase specific drugs. Applying drugs at low concentrations for prolonged periods, however, allows cells with partial resistance to evolve higher levels of resistance through stepwise processes such as gene amplification. Models are developed for cell cycle specific (CS) and cell cycle nonspecific (CNS) drugs to identify the schedule of drug application that balances this tradeoff.The models predict that a CS drug may be applied most effectively by splitting the cumulative dose into many (>40) fractions applied by long-term chemotherapy, while CNS drugs may be better applied in fewer than 10 fractions applied over a shorter term. The model suggests that administering each fraction by continuous infusion may be more effective than giving the drug as a bolus, whether the drug is CS or CNS. In addition, tumors with a low growth fraction or slow rate of cell division are predicted to be controlled more easily with CNS drugs, while those with a high proliferative fraction or fast cell division rate may respond better to CS drugs.

scholarly journals Cell Cycle-Specific Disruption of the Preprophase Band of Microtubules in Fern Protonemata: Effects of Displacement of the Endoplasm by Centrifugation

1992 ◽  
Vol 101 (1) ◽  
pp. 93-98 ◽  
Author(s):  
TAKASHI MURATA ◽  
MASAMITSU WADA
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Plant Cells ◽  
Preprophase Band ◽  
Higher Plant ◽  
The Future ◽  
Prophase Nucleus ◽  
Original Region ◽  
Fern Protonemata

The preprophase band (PPB) of microtubules (MTs), which appears at the future site of cytokinesis prior to cell division in higher plant cells, disappears by metaphase. Recent studies have shown that displacement of the endoplasm from the PPB region by centrifugation delays the disappearance of the PPB. To study the role of the endoplasm in the cell cycle-specific disruption of the PPB, the filamentous protonemal cells of the fern Adiantum capilius-veneris L. were centrifuged twice so that the first centrifugation displaced the endoplasm from the site of the PPB and the second returned it to its original location. The endoplasm, including the nucleus of various stages of mitosis, could be returned by the second centrifugation to the original region of the PPB, which persists during mitosis in the centrifuged cells. When endoplasm with a prophase nucleus was returned to its original location, the PPB was not disrupted. When endoplasm with a prometa-phase telophase nucleus was similarly returned, the PPB was disrupted within 10 min of termination of centrifugation. In protonemal cells of Adiantum, a second PPB is often formed near the displaced nucleus after the first centrifugation. In cells in which the endoplasm was considered to have been returned to its original location at the prophase/prometaphase transition, the second PPB did not disappear even though the initial PPB was disrupted by the endoplasm. These results suggest that cell cycle-specific disruption of the PPB is regulated by some factor(s) in the endoplasm, which appears at prometaphase, i.e. the stage at which the PPB is disrupted in non-centrifuged cells.

scholarly journals p12DOC-1 Is a Novel Cyclin-Dependent Kinase 2-Associated Protein

2000 ◽  
Vol 20 (17) ◽  
pp. 6300-6307 ◽  
Author(s):  
Satoru Shintani ◽  
Hiroe Ohyama ◽  
Xue Zhang ◽  
Jim McBride ◽  
Kou Matsuo ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Ectopic Expression ◽  
Cell Division Cycle ◽  
Cyclin Dependent Kinase ◽  
Data Support ◽  
Normal Keratinocytes ◽  
Active Pool ◽  
Growth Suppressor

ABSTRACT Regulated cyclin-dependent kinase (CDK) levels and activities are critical for the proper progression of the cell division cycle. p12DOC-1 is a growth suppressor isolated from normal keratinocytes. We report that p12DOC-1 associates with CDK2. More specifically, p12DOC-1 associates with the monomeric nonphosphorylated form of CDK2 (p33CDK2). Ectopic expression of p12DOC-1 resulted in decreased cellular CDK2 and reduced CDK2-associated kinase activities and was accompanied by a shift in the cell cycle positions of p12DOC-1transfectants (↑ G1 and ↓ S). The p12DOC-1-mediated decrease of CDK2 was prevented if the p12DOC-1 transfectants were grown in the presence of the proteosome inhibitor clasto-lactacystin β-lactone, suggesting that p12DOC-1 may target CDK2 for proteolysis. A CDK2 binding mutant was created and was found to revert p12DOC-1-mediated, CDK2-associated cell cycle phenotypes. These data support p12DOC-1 as a specific CDK2-associated protein that negatively regulates CDK2 activities by sequestering the monomeric pool of CDK2 and/or targets CDK2 for proteolysis, reducing the active pool of CDK2.

The competence of cells for cell division and regeneration in tobacco explants depends on cellular location, cell cycle phase and ploidy level

Plant Science ◽  
1994 ◽  
Vol 103 (1) ◽  
pp. 81-91 ◽  
Author(s):  
Luud J.W. Gilissen ◽  
Marjo J. van Staveren ◽  
Johanna C. Hakkert ◽  
Marinus J.M. Smulders ◽  
Harrie A. Verhoeven ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Ploidy Level ◽  
Cell Cycle Phase ◽  
Cycle Phase ◽  
Cellular Location

scholarly journals Cell cycle-dependent recruitment of FtsN to the divisome in Escherichia coli

2021 ◽  
Author(s):  
Jaana Mannik ◽  
Sebastien Pichoff ◽  
Joseph Lutkenhaus ◽  
Jaan Mannik
Keyword(s):  
Escherichia Coli ◽  
Cell Cycle ◽  
Cell Division ◽  
Cell Cycle Checkpoint ◽  
Second Stage ◽  
Cycle Checkpoint ◽  
Z Ring ◽  
Lag Period ◽  
Cycle Dependent ◽  
Rate Limiting

Cell division in Escherichia coli starts with the formation of an FtsZ protofilament network in the middle of the cell, the Z ring. However, only after a considerable lag period do the cells start to form a midcell constriction. The basis of this cell cycle checkpoint is yet unclear. The onset of constriction is dependent upon the arrival of so-called late divisome proteins, among which, FtsN is the last arriving essential one. The timing and dependency of FtsN arrival to the divisome, along with genetic evidence, suggests it triggers cell division. In this study, we used high throughput fluorescence microscopy to quantitatively determine the arrival of FtsN and the early divisome protein ZapA to midcell at a single-cell level during the cell cycle. Our data show that recruitment of FtsN coincides with the initiation of constriction within experimental uncertainties and that the relative fraction of ZapA/FtsZ reaches its highest value at this event. We also find that FtsN is recruited to midcell in two distinct temporal stages with septal peptidoglycan synthesis starting in the first stage and accelerating in the second stage, during which the amount of ZapA/FtsZ in the midcell decreases. In the presence of FtsA*, recruitment of FtsN becomes concurrent with the formation of the Z-ring, but constriction is still delayed indicating FtsN recruitment is not rate limiting, at least under these conditions. Finally, our data support the recently proposed idea that ZapA/FtsZ and FtsN are part of physically separate complexes in midcell throughout the whole septation process.

scholarly journals Fission yeast cell cycle mutants and the logic of eukaryotic cell cycle control

2020 ◽  
Vol 31 (26) ◽  
pp. 2871-2873
Author(s):  
Paul Nurse
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Fission Yeast ◽  
Cell Cycle Control ◽  
Eukaryotic Cell ◽  
S Phase ◽  
Cyclin Dependent Kinases ◽  
Starting Point ◽  
Rate Limiting ◽  
Working Out

Cell cycle mutants in the budding and fission yeasts have played critical roles in working out how the eukaryotic cell cycle operates and is controlled. The starting point was Lee Hartwell’s 1970s landmark papers describing the first cell division cycle (CDC) mutants in budding yeast. These mutants were blocked at different cell cycle stages and so were unable to complete the cell cycle, thus defining genes necessary for successful cell division. Inspired by Hartwell’s work, I isolated CDC mutants in the very distantly related fission yeast. This started a program of searches for mutants in fission yeast that revealed a range of phenotypes informative about eukaryotic cell cycle control. These included mutants defining genes that were rate-limiting for the onset of mitosis and of the S-phase, that were responsible for there being only one S-phase in each cell cycle, and that ensured that mitosis only took place when S-phase was properly completed. This is a brief account of the discovery of these mutants and how they led to the identification of cyclin-dependent kinases as core to these cell cycle controls.

scholarly journals Plk is a functional homolog of Saccharomyces cerevisiae Cdc5, and elevated Plk activity induces multiple septation structures.

1997 ◽  
Vol 17 (6) ◽  
pp. 3408-3417 ◽  
Author(s):  
K S Lee ◽  
R L Erikson
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Cell Division ◽  
Specific Activity ◽  
Ectopic Expression ◽  
Sf9 Cells ◽  
Wild Type ◽  
C Terminus ◽  
M Phase

Plk is a mammalian serine/threonine protein kinase whose activity peaks at the onset of M phase. It is closely related to other mammalian kinases, Snk, Fnk, and Prk, as well as to Xenopus laevis Plx1, Drosophila melanogaster polo, Schizosaccharomyces pombe Plo1, and Saccharomyces cerevisiae Cdc5. The M phase of the cell cycle is a highly coordinated process which insures the equipartition of genetic and cellular materials during cell division. To enable understanding of the function of Plk during M phase progression, various Plk mutants were generated and expressed in Sf9 cells and budding yeast. In vitro kinase assays with Plk immunoprecipitates prepared from Sf9 cells indicate that Glu206 and Thr210 play equally important roles for Plk activity and that replacement of Thr210 with a negatively charged residue elevates Plk specific activity. Ectopic expression of wild-type Plk (Plk WT) complements the cell division defect associated with the cdc5-1 mutation in S. cerevisiae. The degree of complementation correlates closely with the Plk activity measured in vitro, as it is enhanced by a mutationally activated Plk, T210D, but is not observed with the inactive forms K82M, D194N, and D194R. In a CDC5 wild-type background, expression of Plk WT or T210D, but not of inactive forms, induced a sharp accumulation of cells in G1. Consistent with elevated Plk activity, this phenomenon was enhanced by the C-terminally deleted forms WT deltaC and T210D deltaC. Expression of T210D also induced a class of cells with unusually elongated buds which developed multiple septal structures. This was not observed with the C-terminally deleted form T210D deltaC, however. It appears that the C terminus of Plk is not required for the observed cell cycle influence but may be important for polarized cell growth and septal structure formation.

scholarly journals Development of double-positive thymocytes at single-cell resolution

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Young Li ◽  
Kun Li ◽  
Lianbang Zhu ◽  
Bin Li ◽  
Dandan Zong ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Flow Cytometry ◽  
T Cells ◽  
Single Cell ◽  
Developmental Stages ◽  
Immunofluorescent Staining ◽  
Cycle Phase ◽  
Specific Gene ◽  
Double Positive ◽  
Species Specific

Abstract Background T cells generated from thymopoiesis are essential for the immune system, and recent single-cell studies have contributed to our understanding of the development of thymocytes at the genetic and epigenetic levels. However, the development of double-positive (DP) T cells, which comprise the majority of thymocytes, has not been well investigated. Methods We applied single-cell sequencing to mouse thymocytes and analyzed the transcriptome data using Seurat. By applying unsupervised clustering, we defined thymocyte subtypes and validated DP cell subtypes by flow cytometry. We classified the cell cycle phases of each cell according to expression of cell cycle phase-specific genes. For immune synapse detection, we used immunofluorescent staining and ImageStream-based flow cytometry. We studied and integrated human thymocyte data to verify the conservation of our findings and also performed cross-species comparisons to examine species-specific gene regulation. Results We classified blast, rearrangement, and selection subtypes of DP thymocytes and used the surface markers CD2 and Ly6d to identify these subtypes by flow cytometry. Based on this new classification, we found that the proliferation of blast DP cells is quite different from that of double-positive cells and other cell types, which tend to exit the cell cycle after a single round. At the DP cell selection stage, we observed that CD8-associated immune synapses formed between thymocytes, indicating that CD8sp selection occurred among thymocytes themselves. Moreover, cross-species comparison revealed species-specific transcription factors (TFs) that contribute to the transcriptional differences of thymocytes from humans and mice. Conclusions Our study classified DP thymocyte subtypes of different developmental stages and provided new insight into the development of DP thymocytes at single-cell resolution, furthering our knowledge of the fundamental immunological process of thymopoiesis.

scholarly journals A Systematic Analysis Identifies Key Regulators Involved in Cell Proliferation and Potential Drugs for the Treatment of Human Lung Adenocarcinoma

2021 ◽  
Vol 11 ◽  
Author(s):  
Kai Wang ◽  
Man Zhang ◽  
Jiao Wang ◽  
Pan Sun ◽  
Jizhuang Luo ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Proliferation ◽  
Cell Division ◽  
Network Analysis ◽  
Lung Adenocarcinoma ◽  
Transcriptional Regulatory Network ◽  
Trichostatin A ◽  
Therapeutic Agents ◽  
Normal Lung ◽  
Specific Gene

Lung adenocarcinoma (LUAD) is one of the most common and malignant cancer types. Abnormal cell proliferation, exemplified by cell cycle and cell division dysregulation, is one of the most prominent hallmarks of cancer and is responsible for recurrence, metastasis, and resistance to cancer therapy. However, LUAD-specific gene regulation and clinical significance remain obscure. Here, by using both tissues and cells from LUAD and normal lung samples, 434 increased and 828 decreased genes of biological significance were detected, including 127 cell cycle-associated genes (95 increased and 32 decreased), 66 cell division-associated genes (56 increased and 10 decreased), and 81 cell proliferation-associated genes (34 increased and 47 decreased). Among them, 12 increased genes (TPX2, CENPF, BUB1, PLK1, KIF2C, AURKB, CDKN3, BUB1B, HMGA2, CDK1, ASPM, and CKS1B) and 2 decreased genes (TACC1 and MYH10) were associated with all the three above processes. Importantly, 2 (CDKN3 and CKS1B) out of the 11 increased genes (except HMGA2) are previously uncharacterized ones in LUAD and can potentially be prognostic markers. Moreover, PLK1 could be a promising therapeutic target for LUAD. Besides, protein–protein interaction network analysis showed that CDK1 and CDC20 were the hub genes, which might play crucial roles in cell proliferation of LUAD. Furthermore, transcriptional regulatory network analysis suggested that the transcription factor E2F1 could be a key regulator in controlling cell proliferation of LUAD via expression modulation of most cell cycle-, cell division-, and cell proliferation-related DEGs. Finally, trichostatin A, hycanthone, vorinostat, and mebeverine were identified as four potential therapeutic agents for LUAD. This work revealed key regulators contributing to cell proliferation in human LUAD and identified four potential therapeutic agents for treatment strategy.

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