scholarly journals Mammalian Rad9 Plays a Role in Telomere Stability, S- and G2-Phase-Specific Cell Survival, and Homologous Recombinational Repair

2006 ◽  
Vol 26 (5) ◽  
pp. 1850-1864 ◽  
Author(s):  
Raj K. Pandita ◽  
Girdhar G. Sharma ◽  
Andrei Laszlo ◽  
Kevin M. Hopkins ◽  
Scott Davey ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Survival ◽  
Cycle Phase ◽  
Specific Cell ◽  
Damage Repair ◽  
Homologous Recombinational Repair ◽  
Mammalian Homologue ◽  
G2 Phase ◽  
Checkpoint Genes ◽  
Kinetics Of

ABSTRACT The protein products of several rad checkpoint genes of Schizosaccharomyces pombe (rad1 +, rad3 +, rad9 +, rad17 +, rad26 +, and hus1 +) play crucial roles in sensing changes in DNA structure, and several function in the maintenance of telomeres. When the mammalian homologue of S. pombe Rad9 was inactivated, increases in chromosome end-to-end associations and frequency of telomere loss were observed. This telomere instability correlated with enhanced S- and G2-phase-specific cell killing, delayed kinetics of γ-H2AX focus appearance and disappearance, and reduced chromosomal repair after ionizing radiation (IR) exposure, suggesting that Rad9 plays a role in cell cycle phase-specific DNA damage repair. Furthermore, mammalian Rad9 interacted with Rad51, and inactivation of mammalian Rad9 also resulted in decreased homologous recombinational (HR) repair, which occurs predominantly in the S and G2 phases of the cell cycle. Together, these findings provide evidence of roles for mammalian Rad9 in telomere stability and HR repair as a mechanism for promoting cell survival after IR exposure.

Phosphatidylcholine catabolism in the MCF-7 cell cycle

2006 ◽  
Vol 84 (5) ◽  
pp. 737-744 ◽  
Author(s):  
Weiyang Lin ◽  
Gilbert Arthur
Keyword(s):  
Cell Cycle ◽  
S Phase ◽  
Specific Cell ◽  
Synchronized Cells ◽  
M Phase ◽  
G2 Phase ◽  
Cell Cycle Phases ◽  
Kinetics Of ◽  
Mcf 7

The catabolism of phosphatidylcholine (PtdCho) appears to play a key role in regulating the net accumulation of the lipid in the cell cycle. Current protocols for measuring the degradation of PtdCho at specific cell-cycle phases require prolonged periods of incubation with radiolabelled choline. To measure the degradation of PtdCho at the S and G2 phases in the MCF-7 cell cycle, protocols were developed with radiolabelled lysophosphatidylcholine (lysoPtdCho), which reduces the labelling period and minimizes the recycling of labelled components. Although most of the incubated lysoPtdCho was hydrolyzed to glycerophosphocholine (GroPCho) in the medium, the kinetics of the incorporation of label into PtdCho suggests that the labelled GroPCho did not contribute significantly to cellular PtdCho formation. A protocol which involved exposing the cells twice to hydroxyurea, was also developed to produce highly synchronized MCF-7 cells with a profile of G1:S:G2/M of 90:5:5. An analysis of PtdCho catabolism in the synchronized cells following labelling with lysoPtdCho revealed that there was increased degradation of PtdCho in early to mid-S phase, which was attenuated in the G2/M phase. The results suggest that the net accumulation of PtdCho in MCF-7 cells may occur in the G2 phase of the cell cycle.

scholarly journals Cell-cycle phase-dependence of drug-induced cycle progression delay.

1979 ◽  
Vol 27 (1) ◽  
pp. 470-473 ◽  
Author(s):  
W Göhde ◽  
M Meistrich ◽  
R Meyn ◽  
J Schumann ◽  
D Johnston ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Chromosomal Abnormalities ◽  
Cell Cycle Phase ◽  
Cycle Phase ◽  
Drug Induced ◽  
Phase Dependence ◽  
Cycle Progression ◽  
G2 Phase ◽  
Phase Progression ◽  
Pulse Cytophotometry

The effect of adriamycin on cell cycle phase progression of CHO cells synchronized into the various phases of the cell cycle by elutriation was investigated by high resolution pulse cytophotometry. Cells treated in all phases of the cell cycle showed delay in their subsequent progression. In addition to the wellknown block of cells in the G2-phase, a delay in passage of cells from G1 to S and a decreased rate of transit through the S-phase were observed. A broadening of the DNA distributions of the treated cells was observed after cell division indicating induction of chromosomal abnormalities.

DNA damage inhibits proteolysis of the B-type cyclin Clb5 in S. cerevisiae

1997 ◽  
Vol 110 (15) ◽  
pp. 1813-1820
Author(s):  
D. Germain ◽  
J. Hendley ◽  
B. Futcher
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Tyrosine Phosphorylation ◽  
Cell Cycle Progression ◽  
Cycle Phase ◽  
Cycle Progression ◽  
Ubiquitin Pathway ◽  
Cyclin Dependent Kinases ◽  
Transition Points ◽  
Checkpoint Genes

Cell cycle progression is mediated by waves of specific cyclin dependent kinases (CDKs) in all eukaryotes. Cyclins are degraded by the ubiquitin pathway of proteolysis. The recent identification of several components of the cyclin proteolysis machinery has highlighted both the importance of proteolysis at multiple transition points in the cell cycle and the involvement of other substrates degraded by the same machinery. In this study, we have investigated the effects of DNA damage on the cyclin proteolytic machinery in Saccharomyces cerevisiae. We find that the half-life of the B-type cyclin Clb5 is markedly increased following DNA damage while that of G1 cyclins is not. This effect is independent of cell cycle phase. Clb5 turnover requires p34CDC28 activity. Stabilisation of Clb5 correlates with an increase in tyrosine phosphorylation of p34CDC28, but stabilisation does not require this tyrosine phosphorylation. The stabilisation is independent of the checkpoint genes Mec1 and Rad53. These observations establish a new link between the regulation of proteolysis and DNA damage.

scholarly journals Measurement of cell-cycle phase-specific cell death using Hoechst 33342 and propidium iodide: preservation by ethanol fixation.

1988 ◽  
Vol 36 (9) ◽  
pp. 1147-1152 ◽  
Author(s):  
G Ciancio ◽  
A Pollack ◽  
M A Taupier ◽  
N L Block ◽  
G L Irvin
Keyword(s):  
Cell Cycle ◽  
Cell Death ◽  
Propidium Iodide ◽  
Cell Cycle Phase ◽  
Cytotoxic Agents ◽  
Cycle Phase ◽  
Specific Cell ◽  
Dead Cell ◽  
Hoechst 33342 ◽  
The Dead

We developed a rapid technique for preservation of Hoechst 33342/propidium iodide-stained cells, using ethanol as a fixative. Combined staining with these dyes makes possible analysis of cell-cycle phase-specific cell death. The technique relies on exclusion of propidium iodide from the viable cells, whereas Hoechst stains all of the cells. The bivariate histograms resulting from the flow cytometric analysis contain the equivalent of two single-parameter DNA histograms, one of the living and the other of the dead cell population. Preservation of staining involved addition of 25% ethanol in PBS after propidium iodide staining and before Hoechst staining. The separation between the living and the dead cell populations was maintained for over 3 days at 4 degrees C. This technique will be valuable for quantitative evaluation of the cell-cycle phase-specific effects of cytostatic or cytotoxic agents, particularly in situations where a lag period between staining and analysis is unavoidable.

Radiosensitive effect of gemcitabine on nasopharyngeal carcinoma CNE-1 cell line

2006 ◽  
Vol 24 (18_suppl) ◽  
pp. 20105-20105
Author(s):  
Y. Chen ◽  
X. Yu
Keyword(s):  
Cell Cycle ◽  
Nasopharyngeal Carcinoma ◽  
Cell Line ◽  
Carcinoma Cell ◽  
Clonogenic Assay ◽  
Flow Cytometric Analysis ◽  
Cell Cycle Phase ◽  
Cycle Phase ◽  
Flow Cytometric ◽  
Damage Repair

20105 Background: To observe the effect and mechanism of gemcitabine-induced radiosensitization on CNE-1 nasopharyngeal carcinoma cell line. Methods: The cell survival curves were obtained with clonogenic assay. The cell cycle phases were measured with flow cytometric analysis. Results: No cytotoxic effect was observed in 0.1 μM and 2 μM gemcitabine alone group. The radiosensitivities were observed in the groups treated with radiation and gemcitabine exposed in different consistencies and times. The SER were 1.35,1.82; 1.55 and 2.16 respectively. The G1 cell cycle phase block was observed in the two consistency groups after exposing to gemcitabine for 24 hours. Dq were rather lower in 2 μM groups especially that exposed for 24 hours. Conclusions: The radiosensitivity was obviously observed in the groups treated with two consistencies of gemcitabine. The effect was more obviously as the consistency and the exposing time increased. The block of cell cycle from G1 to S and the decrease of sublethal damage repair might be contributed to the mechanism. No significant financial relationships to disclose.

Effect of near ultraviolet and visible light on amoeba

1975 ◽  
Vol 19 (1) ◽  
pp. 117-126
Author(s):  
S. Chatterjee ◽  
S.K. Bhattacharjee
Keyword(s):  
Cell Cycle ◽  
Visible Light ◽  
S Phase ◽  
Nuclear Transplantation ◽  
Phase Cell ◽  
Cycle Phase ◽  
Leucine Incorporation ◽  
Repair System ◽  
Near Ultraviolet ◽  
G2 Phase

The near ultraviolet and visible light (VL) impinging at an intensity of 2–5 × 10(2) J s-1 m-2 for 2–5 h kills the mitotic and the early S-phase (0- to 15-min-old) amoebae. At the mid- and late S-period only a fraction of cells are killed by VL and G2 phase cells are quite resistant. Amoebae of all cell cycle stages show a delay in the first mitotic division. DNA synthesis, as measured by [3H]thymidine incorporation, is depressed in the VL-exposed early-S amoebae. A concurrent but temporary inhibition in [3H]leucine incorporation also occurs in these cells. However, no significant change in [3H]uridine incorporation has been found. To localize the site of lethal damage, nuclear transplantation studies were undertaken between the control amoebae and the amoebae treated with VL. The nucleus of a VL-exposed early S-phase cell recovers when transplanted immediately after VL exposure into an enucleate G2 cytoplasm but dies if grafted into an enucleat S-phase cytoplasm. The therapeutic effect of the G2 cytoplasm, although at a lower level, is also evident even when the treated early S-phase nucleus is implanted 20 h later, but not after 48 h, into the G2 cytoplasm. The amoeba cytoplasm shows resistance to VL-irradiation, can accept a control nucleus from any cell cycle stage, and function normally. The G2 nucleus also remains apparently unaffected to VL exposure and can survive when it is transfered to the control cytoplasm of any cell-cycle phase. All these findings are discussed in the light of the possible existence of a repair system against VL-induced damage in the G2-phase amoeba.

Insights into Nano-Photo-Thermal Therapy of Cancer: The Kinetics of Cell Death and Effect on Cell Cycle

2020 ◽  
Vol 20 (5) ◽  
pp. 612-621
Author(s):  
Mousa Tabei ◽  
Elham Zeinizade ◽  
Jaber Beik ◽  
S. Kamran Kamrava ◽  
Zahra Nasiri ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Death ◽  
Cancer Cells ◽  
Signaling Pathway ◽  
Flow Cytometric Analysis ◽  
Thermal Therapy ◽  
Normal Fibroblast ◽  
Cycle Phase ◽  
Flow Cytometric ◽  
Kinetics Of

Background: Despite considerable advances in nano-photo-thermal therapy (NPTT), there have been a few studies reporting in-depth kinetics of cell death triggered by such a new modality of cancer treatment. Objective: In this study, we aimed to (1) investigate the cell death pathways regulating the apoptotic responses to NPTT; and (2) ascertain the effect of NPTT on cell cycle progression. Methods: Folate conjugated gold nanoparticle (F-AuNP) was firstly synthesized, characterized and then assessed to determine its potentials in targeted NPTT. The experiments were conducted on KB nasopharyngeal cancer cells overexpressing folate receptors (FRs), as the model, and L929 normal fibroblast cells with a low level of FRs, as the control. Cytotoxicity was evaluated by MTT assay and the cell death mode (i.e., necrosis or apoptosis) was determined through AnnexinV/FITC-propidium iodide staining. Next, the gene expression profiles of some key apoptotic factors involved in the mitochondrial signaling pathway were investigated using RT-qPCR. Finally, cell cycle phase distribution was investigated at different time points post NPTT using flow cytometric analysis. Results: The obtained results showed that KB cell death following targeted NPTT was greater than that observed for L929 cells. The majority of KB cell death following NPTT was related to apoptosis. RT-qPCR analysis indicated that the elevated expression of Bax along with the depressed expression of Bcl-xL, Survivin and XIAP may involve in the regulation of apoptosis in response to NPTT. Flow cytometric analysis manifested that 16-24 hours after NPTT, the major proportion of KB cells was in the most radiosensitive phases of the cell cycle (G2/M). Conclusion: This study extended the understanding of the signaling pathway involved in the apoptotic response to NPTT. Moreover, the potential effect of NPTT on sensitizing cancer cells to subsequent radiation therapy was highlighted.

scholarly journals SCFSKP2 regulates APC/CCDH1-mediated degradation of CTIP to adjust DNA-end resection in G2-phase

2020 ◽  
Vol 11 (7) ◽  
Author(s):  
Fanghua Li ◽  
Emil Mladenov ◽  
Sharif Mortoga ◽  
George Iliakis
Keyword(s):  
Cell Cycle ◽  
Cell Survival ◽  
S Phase ◽  
Repair Pathway ◽  
End Joining ◽  
Alternative End Joining ◽  
G2 Phase ◽  
Dna End Resection ◽  
Cycle Dependent ◽  
End Resection

Abstract The cell cycle-dependent engagement of DNA-end resection at DSBs is regulated by phosphorylation of CTIP by CDKs, the central regulators of cell cycle transitions. Cell cycle transitions are also intimately regulated by protein degradation via two E3 ubiquitin ligases: SCFSKP2 and APC/CCDH1 complex. Although APC/CCDH1 regulates CTIP in G1– and G2-phase, contributions by SCFSKP2 have not been reported. We demonstrate that SCFSKP2 is a strong positive regulator of resection. Knockdown of SKP2, fully suppresses resection in several cell lines. Notably, this suppression is G2-phase specific and is not observed in S-phase or G1–phase cells. Knockdown of SKP2 inactivates SCFSKP2 causing APC/CCDH1 activation, which degrades CTIP. The stabilizing function of SCFSKP2 on CTIP promotes resection and supports gene conversion (GC), alternative end joining (alt-EJ) and cell survival. We propose that CDKs and SCFSKP2-APC/CCDH1 cooperate to regulate resection and repair pathway choice at DSBs in G2-phase.

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