Changes in the subcellular localization of replication initiation proteins and cell cycle proteins during G1- to S-phase transition in mammalian cells

Chromosoma ◽  
1995 ◽  
Vol 103 (8) ◽  
pp. 517-527 ◽  
Author(s):  
Fran�oise Br�not-Bosc ◽  
Sunita Gupta ◽  
Robert L. Margolis ◽  
Rati Fotedar
Keyword(s):  
Phase Transition ◽  
Cell Cycle ◽  
Subcellular Localization ◽  
Mammalian Cells ◽  
S Phase ◽  
Replication Initiation ◽  
Cell Cycle Proteins ◽  
Replication Initiation Proteins

scholarly journals E2F Is Required To Prevent Inappropriate S-Phase Entry of Mammalian Cells

2000 ◽  
Vol 20 (1) ◽  
pp. 363-371 ◽  
Author(s):  
Song He ◽  
Brian L. Cook ◽  
Benjamin E. Deverman ◽  
Ulrich Weihe ◽  
Fan Zhang ◽  
...  
Keyword(s):  
Phase Transition ◽  
Cell Cycle ◽  
Mammalian Cells ◽  
Cell Types ◽  
S Phase ◽  
Critical Event ◽  
Cell Cycle Genes ◽  
Event Triggering ◽  
Critical Activity ◽  
Phase Entry

ABSTRACT E2F is a family of transcription factors that regulates the cell cycle. It is widely accepted that E2F-mediated transactivation of a set of genes is the critical activity that governs cellular progression through G1 into S phase. In contrast to this hypothesis, we demonstrate that E2F actually suppresses the onset of S phase in two cell types when the cells are arrested by gamma irradiation. Our findings indicate that in these cells, the critical event triggering progression from G0/G1 arrest into S phase is the release of E2F-mediated transrepression of cell cycle genes, not transactivation by E2F. Furthermore, our data suggest that E2F-mediated transactivation is not necessary for the G1/S-phase transition in these cells.

scholarly journals Regulation of DNA Replication Licensing and Re-Replication by Cdt1

2021 ◽  
Vol 22 (10) ◽  
pp. 5195
Author(s):  
Hui Zhang
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Dna Replication ◽  
Genome Stability ◽  
E3 Ligase ◽  
S Phase ◽  
Replication Initiation ◽  
Nuclear Antigen ◽  
Repair Synthesis ◽  
Ubiquitin E3 Ligase

In eukaryotic cells, DNA replication licensing is precisely regulated to ensure that the initiation of genomic DNA replication in S phase occurs once and only once for each mitotic cell division. A key regulatory mechanism by which DNA re-replication is suppressed is the S phase-dependent proteolysis of Cdt1, an essential replication protein for licensing DNA replication origins by loading the Mcm2-7 replication helicase for DNA duplication in S phase. Cdt1 degradation is mediated by CRL4Cdt2 ubiquitin E3 ligase, which further requires Cdt1 binding to proliferating cell nuclear antigen (PCNA) through a PIP box domain in Cdt1 during DNA synthesis. Recent studies found that Cdt2, the specific subunit of CRL4Cdt2 ubiquitin E3 ligase that targets Cdt1 for degradation, also contains an evolutionarily conserved PIP box-like domain that mediates the interaction with PCNA. These findings suggest that the initiation and elongation of DNA replication or DNA damage-induced repair synthesis provide a novel mechanism by which Cdt1 and CRL4Cdt2 are both recruited onto the trimeric PCNA clamp encircling the replicating DNA strands to promote the interaction between Cdt1 and CRL4Cdt2. The proximity of PCNA-bound Cdt1 to CRL4Cdt2 facilitates the destruction of Cdt1 in response to DNA damage or after DNA replication initiation to prevent DNA re-replication in the cell cycle. CRL4Cdt2 ubiquitin E3 ligase may also regulate the degradation of other PIP box-containing proteins, such as CDK inhibitor p21 and histone methylase Set8, to regulate DNA replication licensing, cell cycle progression, DNA repair, and genome stability by directly interacting with PCNA during DNA replication and repair synthesis.

scholarly journals E2F activity is regulated by cell cycle-dependent changes in subcellular localization.

1997 ◽  
Vol 17 (12) ◽  
pp. 7268-7282 ◽  
Author(s):  
R Verona ◽  
K Moberg ◽  
S Estes ◽  
M Starz ◽  
J P Vernon ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Subcellular Localization ◽  
Nuclear Localization ◽  
Mammalian Cells ◽  
Critical Role ◽  
Biological Properties ◽  
Dependent Manner ◽  
Restriction Point ◽  
Cycle Dependent ◽  
Almost All

E2F directs the cell cycle-dependent expression of genes that induce or regulate the cell division process. In mammalian cells, this transcriptional activity arises from the combined properties of multiple E2F-DP heterodimers. In this study, we show that the transcriptional potential of individual E2F species is dependent upon their nuclear localization. This is a constitutive property of E2F-1, -2, and -3, whereas the nuclear localization of E2F-4 is dependent upon its association with other nuclear factors. We previously showed that E2F-4 accounts for the majority of endogenous E2F species. We now show that the subcellular localization of E2F-4 is regulated in a cell cycle-dependent manner that results in the differential compartmentalization of the various E2F complexes. Consequently, in cycling cells, the majority of the p107-E2F, p130-E2F, and free E2F complexes remain in the cytoplasm. In contrast, almost all of the nuclear E2F activity is generated by pRB-E2F. This complex is present at high levels during G1 but disappears once the cells have passed the restriction point. Surprisingly, dissociation of this complex causes little increase in the levels of nuclear free E2F activity. This observation suggests that the repressive properties of the pRB-E2F complex play a critical role in establishing the temporal regulation of E2F-responsive genes. How the differential subcellular localization of pRB, p107, and p130 contributes to their different biological properties is also discussed.

scholarly journals Higher order genomic organization and regulatory compartmentalization for cell cycle control at the G1/S-phase transition

2018 ◽  
Vol 233 (10) ◽  
pp. 6406-6413 ◽  
Author(s):  
Prachi N. Ghule ◽  
David J. Seward ◽  
Andrew J. Fritz ◽  
Joseph R. Boyd ◽  
Andre J. van Wijnen ◽  
...  
Keyword(s):  
Phase Transition ◽  
Cell Cycle ◽  
Genomic Organization ◽  
Cell Cycle Control ◽  
Higher Order ◽  
S Phase

DNA precursor pools and ribonucleotide reductase activity: distribution between the nucleus and cytoplasm of mammalian cells

1985 ◽  
Vol 5 (12) ◽  
pp. 3443-3450
Author(s):  
J M Leeds ◽  
M B Slabaugh ◽  
C K Mathews
Keyword(s):  
Cell Cycle ◽  
Ribonucleotide Reductase ◽  
Cho Cells ◽  
Mammalian Cells ◽  
Plasma Membranes ◽  
Reductase Activity ◽  
Cell Activity ◽  
S Phase ◽  
Whole Cell ◽  
Ribonucleotide Reductase Activity

Nuclear and whole-cell deoxynucleoside triphosphate (dNTP) pools were measured in HeLa cells at different densities and throughout the cell cycle of synchronized CHO cells. Nuclei were prepared by brief detergent (Nonidet P-40) treatment of subconfluent monolayers, a procedure that solubilizes plasma membranes but leaves nuclei intact and attached to the plastic substratum. Electron microscopic examination of monolayers treated with Nonidet P-40 revealed protruding nuclei surrounded by cytoskeletal remnants. Control experiments showed that nuclear dNTP pool sizes were stable during the time required for isolation, suggesting that redistribution of nucleotides during the isolation procedure was minimal. Examination of HeLa whole-cell and nuclear dNTP levels revealed that the nuclear proportion of each dNTP was distinct and remained constant as cell density increased. In synchronized CHO cells, all four dNTP whole-cell pools increased during S phase, with the dCTP pool size increasing most dramatically. The nuclear dCTP pool did not increase as much as the whole-cell dCTP pool during S phase, lowering the relative nuclear dCTP pool. Although the whole-cell dNTP pools decreased after 30 h of isoleucine deprivation, nuclear pools did not decrease proportionately. In summary, nuclear dNTP pools in synchronized CHO cells maintained a relatively constant concentration throughout the cell cycle in the face of larger fluctuations in whole-cell dNTP pools. Ribonucleotide reductase activity was measured in CHO cells throughout the cell cycle, and although there was a 10-fold increase in whole-cell activity during S phase, we detected no reductase in nuclear preparations at any point in the cell cycle.

Cell cycle variations of dinucleoside polyphosphates in synchronized cultures of mammalian cells

1987 ◽  
Vol 7 (7) ◽  
pp. 2444-2450
Author(s):  
G Orfanoudakis ◽  
M Baltzinger ◽  
D Meyer ◽  
N Befort ◽  
J P Ebel ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Mammalian Cells ◽  
S Phase ◽  
Serum Deprivation ◽  
Specific Cell ◽  
Culture Cells ◽  
Mouse Embryo Fibroblasts ◽  
Atp Pool ◽  
Dinucleoside Polyphosphates ◽  
Synchronized Cultures

Zajdela hepatoma culture cells (ZHC) and mouse embryo fibroblasts (Swiss 3T3) were synchronized in G1 or S phase by serum deprivation and aphidicolin treatment, respectively, to study the variations in adenylyl nucleotide (Ap4X) pool size during the progress of the cell cycle. Only minor variations, which never exceeded a factor of 2, were observed when the Ap4X concentrations were expressed on a cellular basis. The variations were found to be strictly parallel to the ATP variations. Upon release from an aphidicolin block, the minor variations of Ap4X followed DNA synthesis and preceded cytokinesis. When the nucleotide content was compared with the amount of proteins, the faint specific cell cycle changes were almost completely damped when the cells were synchronized by serum deprivation, but remained practically unchanged in the case of aphidicolin synchronization. These results suggest that the observed variations could reflect the accumulation of some nucleotides before cell division. It is not clear yet whether the variation in Ap4X concentration is significant by itself or is simply a phenomenon resulting from changes in the ATP pool.

scholarly journals Evidence for DNA-PK-dependent and -independent DNA double-strand break repair pathways in mammalian cells as a function of the cell cycle.

1997 ◽  
Vol 17 (3) ◽  
pp. 1425-1433 ◽  
Author(s):  
S E Lee ◽  
R A Mitchell ◽  
A Cheng ◽  
E A Hendrickson
Keyword(s):  
Cell Cycle ◽  
Mammalian Cells ◽  
Cellular Response ◽  
Strand Break ◽  
S Phase ◽  
Dependent Manner ◽  
Severe Combined Immune Deficiency ◽  
Dsb Repair ◽  
G2 Checkpoint ◽  
G2 Phase

Mice homozygous for the scid (severe combined immune deficiency) mutation are defective in the repair of DNA double-strand breaks (DSBs) and are consequently very X-ray sensitive and defective in the lymphoid V(D)J recombination process. Recently, a strong candidate for the scid gene has been identified as the catalytic subunit of the DNA-dependent protein kinase (DNA-PK) complex. Here, we show that the activity of the DNA-PK complex is regulated in a cell cycle-dependent manner, with peaks of activity found at the G1/early S phase and again at the G2 phase in wild-type cells. Interestingly, only the deficit of the G1/early S phase DNA-PK activity correlated with an increased hypersensitivity to X-irradiation and a DNA DSB repair deficit in synchronized scid pre-B cells. Finally, we demonstrate that the DNA-PK activity found at the G2 phase may be required for exit from a DNA damage-induced G2 checkpoint arrest. These observations suggest the presence of two pathways (DNA-PK-dependent and -independent) of illegitimate mammalian DNA DSB repair and two distinct roles (DNA DSB repair and G2 checkpoint traversal) for DNA-PK in the cellular response to ionizing radiation.

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