scholarly journals Correlation between DNA synthesis in the second, third and fourth generations of spermatogonia and the occurrence of apoptosis in both spermatogonia and spermatocytes

Reproduction ◽  
2003 ◽  
pp. 661-668 ◽  
Author(s):  
J Blanco-Rodriguez ◽  
C Martinez-Garcia ◽  
A Porras
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Dna Synthesis ◽  
Functional Significance ◽  
Tunel Assay ◽  
Seminiferous Epithelium ◽  
Cell Cycle Checkpoints ◽  
Clear Correlation ◽  
Cellular Events ◽  
Dna Strand

In the seminiferous epithelium, both DNA synthesis and apoptosis occur at equivalent stages in various species, with apoptosis taking place mainly at the same stages as DNA replication in the second, third and fourth spermatogonial generations. As preservation of the cellular associations found at these stages may have some functional significance, it is important to determine whether there is a correlation between these cellular events. In this study, pairs of immunoperoxidase-stained adjacent testis sections from rats, mice, rabbits and cats in which either bromodeoxyuridine incorporated into the newly synthesized DNA strand (BrdU labelling) or DNA 3' end labelling of the apoptotic DNA fragments (TUNEL assay) were detected were compared. In addition, both events were analysed in double-labelled sections. These two methods revealed a clear correlation between the occurrence of DNA replication in the second to fourth generations of spermatogonia and most physiological apoptosis taking place in both spermatogonia and spermatocytes in the three different mammalian orders (Rodentia, Lagomorpha and Carnivora). This correlation may result from the synchronization of mitotic spermatogonial and meiotic spermatocyte cell cycle checkpoints operating at these stages.

Effect of inhibitors of DNA replication on early zebrafish embryos: evidence for coordinate activation of multiple intrinsic cell-cycle checkpoints at the mid-blastula transition

Zygote ◽  
1997 ◽  
Vol 5 (2) ◽  
pp. 153-175 ◽  
Author(s):  
Richard Ikegami ◽  
Alma K. Rivera-Bennetts ◽  
Deborah L. Brooker ◽  
Thomas D. Yager
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Dna Synthesis ◽  
Adaptive Response ◽  
Topoisomerase I ◽  
Topoisomerase Ii ◽  
Cell Cycle Checkpoints ◽  
Zebrafish Embryos ◽  
Replication Process ◽  
Inhibition Of Dna Synthesis

SummaryWe address the developmental activation, in the zebrafish embryo, of intrinsic cell-cycle checkpoints which monitor the DNA replication process and progression through the cell cycle. Eukaryotic DNA replication is probably carried out by a multiprotein complex containing numerous enzymes and accessory factors that act in concert to effect processive DNA synthesis (Applegren, N. et al. (1995) J. Cell. Biochem. 59, 91–107). We have exposed early zebrafish embryos to three chemical agents which are predicted to specifically inhibit the DNA polymerase α, topoisomerase I and topoisomerase II components of the DNA replication complex. We present four findings: (1) Before mid-blastula transition (MBT) an inhibition of DNA synthesis does not block cells from attempting to proceed through mitosis, implying the lack of functional checkpoints. (2) After MBT, the embryo displays two distinct modes of intrinsic checkpoint operation. One mode is a rapid and complete stop of cell division, and the other is an ‘adaptive’ response in which the cell cycle continues to operate, perhaps in a ‘repair’ mode, to generate daughter nuclei with few visible defects. (3) The embryo does not display a maximal capability for the ‘adaptive’ response until several hours after MBT, which is consistent with a slow rranscriptional control mechanism for checkpoint activation. (4) The slow activation of checkpoints at MBT provides a window of time during which inhibitors of DNA synthesis will induce cytogenetic lesions without killing the embryo. This could be useful in the design of a deletion-mutagenesis strategy.

scholarly journals Polycomb proteins control proliferation and transformation independently of cell cycle checkpoints by regulating DNA replication

2014 ◽  
Vol 5 (1) ◽  
Author(s):  
Andrea Piunti ◽  
Alessandra Rossi ◽  
Aurora Cerutti ◽  
Mareike Albert ◽  
Sriganesh Jammula ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Cell Cycle Checkpoints ◽  
Polycomb Proteins

scholarly journals DNA damage-induced cell cycle checkpoints and DNA strand break repair in development and tumorigenesis

Oncogene ◽  
1999 ◽  
Vol 18 (55) ◽  
pp. 7883-7899 ◽  
Author(s):  
Gopal K Dasika ◽  
Suh-Chin J Lin ◽  
Song Zhao ◽  
Patrick Sung ◽  
Alan Tomkinson ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Strand Break ◽  
Cell Cycle Checkpoints ◽  
Dna Strand Break ◽  
Break Repair ◽  
Dna Strand

scholarly journals Nonperiodic Activity of the Human Anaphase-Promoting Complex–Cdh1 Ubiquitin Ligase Results in Continuous DNA Synthesis Uncoupled from Mitosis

2000 ◽  
Vol 20 (20) ◽  
pp. 7613-7623 ◽  
Author(s):  
Claus Storgaard Sørensen ◽  
Claudia Lukas ◽  
Edgar R. Kramer ◽  
Jan-Michael Peters ◽  
Jiri Bartek ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Dna Replication ◽  
Dna Synthesis ◽  
Ubiquitin Ligase ◽  
Mammalian Cells ◽  
Kinase Inhibitor ◽  
Cyclin B1 ◽  
S Phase ◽  
Anaphase Promoting Complex

ABSTRACT Ubiquitin-proteasome-mediated destruction of rate-limiting proteins is required for timely progression through the main cell cycle transitions. The anaphase-promoting complex (APC), periodically activated by the Cdh1 subunit, represents one of the major cellular ubiquitin ligases which, in Saccharomyces cerevisiae andDrosophila spp., triggers exit from mitosis and during G1 prevents unscheduled DNA replication. In this study we investigated the importance of periodic oscillation of the APC-Cdh1 activity for the cell cycle progression in human cells. We show that conditional interference with the APC-Cdh1 dissociation at the G1/S transition resulted in an inability to accumulate a surprisingly broad range of critical mitotic regulators including cyclin B1, cyclin A, Plk1, Pds1, mitosin (CENP-F), Aim1, and Cdc20. Unexpectedly, although constitutively assembled APC-Cdh1 also delayed G1/S transition and lowered the rate of DNA synthesis during S phase, some of the activities essential for DNA replication became markedly amplified, mainly due to a progressive increase of E2F-dependent cyclin E transcription and a rapid turnover of the p27Kip1 cyclin-dependent kinase inhibitor. Consequently, failure to inactivate APC-Cdh1 beyond the G1/S transition not only inhibited productive cell division but also supported slow but uninterrupted DNA replication, precluding S-phase exit and causing massive overreplication of the genome. Our data suggest that timely oscillation of the APC-Cdh1 ubiquitin ligase activity represents an essential step in coordinating DNA replication with cell division and that failure of mechanisms regulating association of APC with the Cdh1 activating subunit can undermine genomic stability in mammalian cells.

scholarly journals Identification of an Arginine-Rich Motif in Human Papillomavirus Type 1 E1^E4 Protein Necessary for E4-Mediated Inhibition of Cellular DNA Synthesis In Vitro and in Cells

2008 ◽  
Vol 82 (18) ◽  
pp. 9056-9064 ◽  
Author(s):  
Sally Roberts ◽  
Sarah R. Kingsbury ◽  
Kai Stoeber ◽  
Gillian L. Knight ◽  
Phillip H. Gallimore ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Dna Synthesis ◽  
Host Cell ◽  
S Phase ◽  
Human Papillomaviruses ◽  
Soluble Form ◽  
Cellular Dna ◽  
In Cells

ABSTRACT Productive infections by human papillomaviruses (HPVs) are restricted to nondividing, differentiated keratinocytes. HPV early proteins E6 and E7 deregulate cell cycle progression and activate the host cell DNA replication machinery in these cells, changes essential for virus synthesis. Productive virus replication is accompanied by abundant expression of the HPV E4 protein. Expression of HPV1 E4 in cells is known to activate cell cycle checkpoints, inhibiting G2-to-M transition of the cell cycle and also suppressing entry of cells into S phase. We report here that the HPV1 E4 protein, in the presence of a soluble form of the replication-licensing factor (RLF) Cdc6, inhibits initiation of cellular DNA replication in a mammalian cell-free DNA replication system. Chromatin-binding studies show that E4 blocks replication initiation in vitro by preventing loading of the RLFs Mcm2 and Mcm7 onto chromatin. HPV1 E4-mediated replication inhibition in vitro and suppression of entry of HPV1 E4-expressing cells into S phase are both abrogated upon alanine replacement of arginine 45 in the full-length E4 protein (E1^E4), implying that these two HPV1 E4 functions are linked. We hypothesize that HPV1 E4 inhibits competing host cell DNA synthesis in replication-activated suprabasal keratinocytes by suppressing licensing of cellular replication origins, thus modifying the phenotype of the infected cell in favor of viral genome amplification.

scholarly journals RB Reversibly Inhibits DNA Replication via Two Temporally Distinct Mechanisms

2004 ◽  
Vol 24 (12) ◽  
pp. 5404-5420 ◽  
Author(s):  
Steven P. Angus ◽  
Christopher N. Mayhew ◽  
David A. Solomon ◽  
Wesley A. Braden ◽  
Michael P. Markey ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Dna Synthesis ◽  
Cellular Proliferation ◽  
Negative Regulator ◽  
Proliferating Cells ◽  
Factor C ◽  
Replication Factors ◽  
Multiple Replication

ABSTRACT The retinoblastoma (RB) tumor suppressor is a critical negative regulator of cellular proliferation. Repression of E2F-dependent transcription has been implicated as the mechanism through which RB inhibits cell cycle progression. However, recent data have suggested that the direct interaction of RB with replication factors or sites of DNA synthesis may contribute to its ability to inhibit S phase. Here we show that RB does not exert a cis-acting effect on DNA replication. Furthermore, the localization of RB was distinct from replication foci in proliferating cells. While RB activation strongly attenuated the RNA levels of multiple replication factors, their protein expression was not diminished coincident with cell cycle arrest. During the first 24 h of RB activation, components of the prereplication complex, initiation factors, and the clamp loader complex (replication factor C) remained tethered to chromatin. In contrast, the association of PCNA and downstream components of the processive replication machinery was specifically disrupted. This signaling from RB occurred in a manner dependent on E2F-mediated transcriptional repression. Following long-term activation of RB, we observed the attenuation of multiple replication factors, the complete cessation of DNA synthesis, and impaired replicative capacity in vitro. Therefore, functional distinctions exist between the “chronic” RB-mediated arrest state and the “acute” arrest state. Strikingly, attenuation of RB activity reversed both acute and chronic replication blocks. Thus, continued RB action is required for the maintenance of two kinetically and functionally distinct modes of replication inhibition.

scholarly journals Evidence that the cell cycle is a series of uncoupled, memoryless phases

2018 ◽  
Author(s):  
Hui Xiao Chao ◽  
Randy I. Fakhreddin ◽  
Hristo K. Shimerov ◽  
Rashmi J. Kumar ◽  
Gaorav P. Gupta ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Cell Cycle Progression ◽  
Phase 1 ◽  
Cell Cycle Phase ◽  
Cell Cycle Checkpoints ◽  
Cycle Phase ◽  
Erlang Distribution ◽  
Cycle Progression ◽  
Gap Phase

The cell cycle is canonically described as a series of 4 phases: G1 (gap phase 1), S (DNA synthesis), G2 (gap phase 2), and M (mitosis). Various models have been proposed to describe the durations of each phase, including a two-state model with fixed S-G2-M duration and random G1 duration1,2; a “stretched” model in which phase durations are proportional3; and an inheritance model in which sister cells show correlated phase durations2,4. A fundamental challenge is to understand the quantitative laws that govern cell-cycle progression and to reconcile the evidence supporting these different models. Here, we used time-lapse fluorescence microscopy to quantify the durations of G1, S, G2, and M phases for thousands of individual cells from three human cell lines. We found no evidence of correlation between any pair of phase durations. Instead, each phase followed an Erlang distribution with a characteristic rate and number of steps. These observations suggest that each cell cycle phase is memoryless with respect to previous phase durations. We challenged this model by perturbing the durations of specific phases through oncogene activation, inhibition of DNA synthesis, reduced temperature, and DNA damage. Phase durations remained uncoupled in individual cells despite large changes in durations in cell populations. To explain this behavior, we propose a mathematical model in which the independence of cell-cycle phase durations arises from a large number of molecular factors that each exerts a minor influence on the rate of cell-cycle progression. The model predicts that it is possible to force correlations between phases by making large perturbations to a single factor that contributes to more than one phase duration, which we confirmed experimentally by inhibiting cyclin-dependent kinase 2 (CDK2). We further report that phases can show coupling under certain dysfunctional states such as in a transformed cell line with defective cell cycle checkpoints. This quantitative model of cell cycle progression explains the paradoxical observation that phase durations are both inherited and independent and suggests how cell cycle progression may be altered in disease states.

scholarly journals Protein phosphatase 2A (PP2A) promotes anaphase entry after DNA replication stress in budding yeast

2021 ◽  
Author(s):  
Cory Haluska ◽  
Fengzhi Jin ◽  
Yanchang Wang
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Dna Synthesis ◽  
Protein Phosphatase ◽  
Budding Yeast ◽  
Replication Stress ◽  
S Phase ◽  
Viability Loss ◽  
Phosphatase 2A ◽  
Dna Replication Stress

DNA replication stress activates the S-phase checkpoint that arrests the cell cycle, but it is poorly understood how cells recover from this arrest. Cyclin-dependent kinase (CDK) and Protein Phosphatase 2A (PP2A) are key cell cycle regulators, and Cdc55 is a regulatory subunit of PP2A in budding yeast. We found that yeast cells lacking functional PP2ACdc55 showed slow growth in the presence of hydroxyurea (HU), a DNA synthesis inhibitor, without obvious viability loss. Moreover, PP2A mutants exhibited delayed anaphase entry and sustained levels of anaphase inhibitor Pds1 after HU treatment. A DNA damage checkpoint Chk1 phosphorylates and stabilizes Pds1. We showed that chk1Δ and mutation of the Chk1 phosphorylation sites in Pds1 largely restored efficient anaphase entry in PP2A mutants after HU treatment. In addition, deletion of SWE1 that encodes the inhibitory kinase for CDK or mutation of the Swe1 phosphorylation site in CDK ( cdc28F19) also suppressed the anaphase entry delay in PP2A mutants after HU treatment. Our genetic data suggest that Swe1/CDK acts upstream of Pds1. Surprisingly, cdc55Δ showed significant suppression to the viability loss of S-phase checkpoint mutants during DNA synthesis block. Together, our results uncover a PP2A-Swe1-CDK-Chk1-Pds1 axis that promotes recovery from DNA replication stress.

scholarly journals Human Exonuclease 1 (EXO1) Regulatory Functions in DNA Replication with Putative Roles in Cancer

2018 ◽  
Vol 20 (1) ◽  
pp. 74 ◽  
Author(s):  
Guido Keijzers ◽  
Daniela Bakula ◽  
Michael Petr ◽  
Nils Madsen ◽  
Amanuel Teklu ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Repair ◽  
Dna Replication ◽  
Replication Fork ◽  
Cellular Transformation ◽  
Cell Cycle Checkpoints ◽  
Replication Process ◽  
Exonuclease 1 ◽  
Repair Pathways ◽  
Regulatory Functions

Human exonuclease 1 (EXO1), a 5′→3′ exonuclease, contributes to the regulation of the cell cycle checkpoints, replication fork maintenance, and post replicative DNA repair pathways. These processes are required for the resolution of stalled or blocked DNA replication that can lead to replication stress and potential collapse of the replication fork. Failure to restart the DNA replication process can result in double-strand breaks, cell-cycle arrest, cell death, or cellular transformation. In this review, we summarize the involvement of EXO1 in the replication, DNA repair pathways, cell cycle checkpoints, and the link between EXO1 and cancer.

A human nuclear protein with sequence homology to a family of early S phase proteins is required for entry into S phase and for cell division

1994 ◽  
Vol 107 (1) ◽  
pp. 253-265 ◽  
Author(s):  
I.T. Todorov ◽  
R. Pepperkok ◽  
R.N. Philipova ◽  
S.E. Kearsey ◽  
W. Ansorge ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Amino Acid ◽  
Dna Replication ◽  
Dna Synthesis ◽  
Mammalian Cells ◽  
Nuclear Protein ◽  
Amino Acid Level ◽  
S Phase ◽  
Significant Similarity

Molecular cloning and characterisation of a human nuclear protein designated BM28 is reported. On the amino acid level this 892 amino acid protein, migrating on SDS-gels as a 125 kDa polypeptide, shares areas of significant similarity with a recently defined family of early S phase proteins. The members of this family, the Saccharomyces cerevisiae Mcm2p, Mcm3p, Cdc46p/Mcm5p, the Schizosaccharomyces pombe Cdc21p and the mouse protein P1 are considered to be involved in the onset of DNA replication. The highest similarity was found with Mcm2p (42% identity over the whole length and higher than 75% over a conservative region of 215 amino acid residues), suggesting that BM28 could represent the human homologue of the S. cerevisiae MCM2. Using antibodies raised against the recombinant BM28 the corresponding antigen was found to be localised in the nuclei of various mammalian cells. Microinjection of anti-BM28 antibody into synchronised mouse NIH3T3 or human HeLa cells presents evidence for the involvement of the protein in cell cycle progression. When injected in G1 phase the anti-BM28 antibody inhibits the onset of subsequent DNA synthesis as tested by the incorporation of bromodeoxyuridine. Microinjection during the S phase had no effect on DNA synthesis, but inhibits cell division. The data suggest that the nuclear protein BM28 is required for two events of the cell cycle, for the onset of DNA replication and for cell division.

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