Analyzing Cell Cycle Checkpoints in Response to Ionizing Radiation in Mammalian Cells

2014 ◽  
pp. 313-320 ◽  
Author(s):  
Bin Wang
Keyword(s):  
Cell Cycle ◽  
Ionizing Radiation ◽  
Mammalian Cells ◽  
Cell Cycle Checkpoints

Cell cycle progression and cell division are sensitive to hypoxia in Drosophila melanogaster embryos

2001 ◽  
Vol 280 (5) ◽  
pp. R1555-R1563 ◽  
Author(s):  
Robert M. Douglas ◽  
Tian Xu ◽  
Gabriel G. Haddad
Keyword(s):  
Cell Cycle ◽  
Drosophila Melanogaster ◽  
Mammalian Cells ◽  
Fluorescent Protein ◽  
Immunoblot Analysis ◽  
Embryonic Cell ◽  
Cell Cycle Checkpoints ◽  
Cycle Phase ◽  
Embryonic Cells

We and others recently demonstrated that Drosophila melanogaster embryos arrest development and embryonic cells cease dividing when they are deprived of O2. To further characterize the behavior of these embryos in response to O2 deprivation and to define the O2-sensitive checkpoints in the cell cycle, embryos undergoing nuclear cycles 3–13 were subjected to O2deprivation and examined by confocal microscopy under control, hypoxic, and reoxygenation conditions. In vivo, real-time analysis of embryos carrying green fluorescent protein-kinesin demonstrated that cells arrest at two major points of the cell cycle, either at the interphase (before DNA duplication) or at metaphase, depending on the cell cycle phase at which O2 deprivation was induced. Immunoblot analysis of embryos whose cell divisions are synchronized by inducible String (cdc25 homolog) demonstrated that cyclin B was degraded during low O2 conditions in interphase-arrested embryos but not in those arrested in metaphase. Embryos resumed cell cycle activity within ∼20 min of reoxygenation, with very little apparent change in cell cycle kinetics. We conclude that there are specific points during the embryonic cell cycle that are sensitive to the O2 level in D. melanogaster. Given the fact that O2deprivation also influences the growth and development of other species, we suggest that similar hypoxia-sensitive cell cycle checkpoints may also exist in mammalian cells.

scholarly journals Involvement of Brca1 in S-Phase and G2-Phase Checkpoints after Ionizing Irradiation

2001 ◽  
Vol 21 (10) ◽  
pp. 3445-3450 ◽  
Author(s):  
Bo Xu ◽  
Seong-tae Kim ◽  
Michael B. Kastan
Keyword(s):  
Cell Cycle ◽  
Mammalian Cells ◽  
Cellular Responses ◽  
S Phase ◽  
Cell Cycle Checkpoints ◽  
Genetic Damage ◽  
Ionizing Irradiation ◽  
Direct Role ◽  
G2 Phase ◽  
Definitive Role

ABSTRACT Cell cycle arrests in the G1, S, and G2phases occur in mammalian cells after ionizing irradiation and appear to protect cells from permanent genetic damage and transformation. Though Brca1 clearly participates in cellular responses to ionizing radiation (IR), conflicting conclusions have been drawn about whether Brca1 plays a direct role in cell cycle checkpoints. Normal Nbs1 function is required for the IR-induced S-phase checkpoint, but whether Nbs1 has a definitive role in the G2/M checkpoint has not been established. Here we show that Atm and Brca1 are required for both the S-phase and G2 arrests induced by ionizing irradiation while Nbs1 is required only for the S-phase arrest. We also found that mutation of serine 1423 in Brca1, a target for phosphorylation by Atm, abolished the ability of Brca1 to mediate the G2/M checkpoint but did not affect its S-phase function. These results clarify the checkpoint roles for each of these three gene products, demonstrate that control of cell cycle arrests must now be included among the important functions of Brca1 in cellular responses to DNA damage, and suggest that Atm phosphorylation of Brca1 is required for the G2/M checkpoint.

scholarly journals Checkpoint non-fidelity induces a complex landscape of lineage fitness after DNA damage

2018 ◽  
Author(s):  
Callum J. Campbell ◽  
Ashok R. Venkitaraman ◽  
Alessandro Esposito
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Cell Fate ◽  
Mammalian Cells ◽  
Cell Cycle Progression ◽  
Dna Lesions ◽  
Lineage Tracing ◽  
Cell Cycle Checkpoints ◽  
Complex Landscape ◽  
Cellular Dna

AbstractDNA damage in proliferating mammalian cells causes death1, senescence2 or continued survival, via checkpoints that monitor damage and regulate cell cycle progression, DNA repair and fate determination3. Cell cycle checkpoints facilitate tumour suppression by preventing the generation of proliferating mutated cells4, particularly by blocking passage of DNA lesions into replication and mitosis5. While checkpoint non-fidelity permits cells to carry genomic aberrations into subsequent cell cycle phases6, its long-term consequences on lineages descendant from damaged cells remains poorly characterised. Devising methods for microscopy-based lineage tracing, we unexpectedly demonstrate that transient DNA damage to single living cells bearing a negligent checkpoint induces heterogenous cell-fate outcomes in their descendant generations removed from the initial insult. After transiently damaged cells undergo an initial arrest, pairs of descendant cells without obvious cell-cycle abnormalities either divide or die in a seemingly stochastic way. Progeny of transiently damaged cells may die generations afterwards, creating considerable variability of lineage fitness that promotes overall persistence in a mutagenic environment. Descendants of damaged cells frequently form micronuclei, activating immunogenic signalling. Our findings reveal previously unrecognized, heterogenous effects of cellular DNA damage that manifest long afterwards in descendant cells. We suggest that these heterogenous descendant cell-fate responses may function physiologically to ensure the elimination and immune clearance of damaged cell lineages, but pathologically, may enable the prolonged survival of cells bearing mutagenic damage.

Ion channels and transporters in cancer. 1. Ion channels and cell proliferation in cancer

2011 ◽  
Vol 301 (2) ◽  
pp. C255-C265 ◽  
Author(s):  
Andrea Becchetti
Keyword(s):  
Cell Cycle ◽  
Cell Proliferation ◽  
Ion Channels ◽  
Mammalian Cells ◽  
Malignant Cell ◽  
Cell Cycle Checkpoints ◽  
Environmental Signals ◽  
Functional Flexibility ◽  
Research Fields ◽  
Functional Relations

Progress through the cell mitotic cycle requires precise timing of the intrinsic molecular steps and tight coordination with the environmental signals that maintain a cell into the proper physiological context. Because of their great functional flexibility, ion channels coordinate the upstream and downstream signals that converge on the cell cycle machinery. Both voltage- and ligand-gated channels have been implicated in the control of different cell cycle checkpoints in normal as well as neoplastic cells. Ion channels mediate the calcium signals that punctuate the mitotic process, the cell volume oscillations typical of cycling cells, and the exocytosis of autocrine or angiogenetic factors. Other functions of ion channels in proliferation are still matter of debate. These may or may not depend on ion transport, as the channel proteins can form macromolecular complexes with growth factor and cell adhesion receptors. Direct conformational coupling with the cytoplasmic regulatory proteins is also possible. Derangement or relaxed control of the above processes can promote neoplasia. Specific types of ion channels have turned out to participate in the different stages of the tumor progression, in which cell heterogeneity is increased by the selection of malignant cell clones expressing the ion channel types that better support unrestrained growth. However, a comprehensive mechanistic picture of the functional relations between ion channels and cell proliferation is yet not available, partly because of the considerable experimental challenges offered by studying these processes in living mammalian cells. No doubt, such studies will constitute one of the most fruitful research fields for the next generation of cell physiologists.

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