scholarly journals Deficiencies in DNA replication and cell-cycle progression in polyamine-depleted HeLa cells

1992 ◽  
Vol 281 (1) ◽  
pp. 87-93 ◽  
Author(s):  
R A Koza ◽  
E J Herbst
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Dna Polymerase ◽  
Hela Cells ◽  
Control Point ◽  
Control Cell ◽  
Alpha Activity ◽  
S Phase ◽  
Cell Nuclei ◽  
Dna Polymerase Alpha

Synchronized HeLa cells depleted of polyamines by alpha-difluoromethylornithine exhibited substantially decreased DNA synthesis, and proliferation ceased after the release of the cells into S phase. Nuclei from these cells synthesized 70-80% less DNA than did nuclei from control cells. Extraction of isolated nuclei with 0.3 M-KCl decreased DNA synthesis by about 60%, which was recovered almost completely in control cell nuclei by reconstitution with the salt extracts of these nuclei. On the other hand, salt extracts of polyamine-depleted nuclei restored only 50% of DNA synthesis in extracted control nuclei. Salt extracts of control cell nuclei contained twice the DNA polymerase alpha activity of polyamine-depleted nuclear extracts. Extracts of cell lysates of both control and polyamine-depleted HeLa cells exhibited similar DNA polymerase alpha activity, suggesting that uptake of the enzyme or its retention by the nuclei of polyamine-depleted cells was decreased. Polyamine-depleted nuclei also showed altered phosphorylation of a 31 kDa protein as compared with control nuclei. Almost normal DNA synthesis, cell proliferation, DNA polymerase alpha activity and nuclear protein phosphorylation were restored in polyamine-depleted cells grown in medium supplemented with 20 microM-spermidine at least 10-12 h before S phase. Cultures in which proliferation was blocked by alpha-difluoromethylornithine did not exhibit synchronous growth after the block was removed. Thus it may be concluded that HeLa cells depleted of polyamines are not inhibited at a single control point in the cell cycle, but are arrested at diverse sites throughout G1 phase.

scholarly journals Involvement of deoxyribonucleic acid polymerase β in nuclear deoxyribonucleic acid synthesis

1978 ◽  
Vol 173 (1) ◽  
pp. 309-314 ◽  
Author(s):  
T R Butt ◽  
W M Wood ◽  
E L McKay ◽  
R L P Adams
Keyword(s):  
Dna Synthesis ◽  
Dna Polymerase ◽  
Deoxyribonucleic Acid ◽  
Nuclear Dna ◽  
Dna Polymerase Beta ◽  
Cell Nuclei ◽  
High Molecular Weight Dna ◽  
Dna Polymerase Alpha ◽  
Polymerase Beta

The effects on DNA synthesis in vitro in mouse L929-cell nuclei of differential extraction of DNA polymerases alpha and beta were studied. Removal of all measurable DNA polymerase alpha and 20% of DNA polymerase beta leads to a 40% fall in the replicative DNA synthesis. Removal of 70% of DNA polymerase beta inhibits replicative synthesis by 80%. In all cases the nuclear DNA synthesis is sensitive to N-ethylmaleimide and aCTP (arabinosylcytosine triphosphate), though less so than DNA polymerase alpha. Addition of deoxyribonuclease I to the nuclear incubation leads to synthesis of high-molecular-weight DNA in a repair reaction. This occurs equally in nuclei from non-growing or S-phase cells. The former nuclei lack DNA polymerase alpha and the reaction reflects the sensitivity of DNA polymerase beta to inhibiton by N-ethylmaleimide and aCTP.

scholarly journals Effect of drugs on deoxyribonucleic acid synthesis in isolated mammalian cell nuclei. Comparison with partially purified deoxyribonucleic acid polymerases

1979 ◽  
Vol 178 (3) ◽  
pp. 621-626 ◽  
Author(s):  
J F Burke ◽  
P M Duff ◽  
C K Pearson
Keyword(s):  
Dna Synthesis ◽  
Dna Polymerase ◽  
Deoxyribonucleic Acid ◽  
Acid Synthesis ◽  
Cell Nuclei ◽  
Isolated Nuclei ◽  
Dna Polymerase Alpha ◽  
Polymerase Beta ◽  
Deoxyribonucleic Acid Synthesis

In order to ascertain the identity of the DNA-dependent DNA polymerase responsible for the observed DNA synthesis in nuclei isolated from baby-hamster kidney (BHK-21/C13) cells a comparative study was carried out on the effects of some drugs, reported to influence DNA synthesis, on DNA synthesis catalysed by these nuclei and by partially purified DNA polymerase-alpha and -beta. In all cases DNA synthesis by isolated nuclei and polymerase-alpha was inhibited to similar extents by N-ethylmaleimide, p-hydroxymercuribenzoate, novobiocin, heparin and phosphonoacetic acid; polymerase-beta was much less affected by these compounds. Ethidium bromide inhibited all DNA synthesis to similar extents, although at low concentrations (about 2 microgram/ml) synthesis in isolated nuclei was stimulated. The results are discussed in relation to the proposal that DNA polymerase-alpha catalyses the covalent extension of Okazaki fragments that these nuclei carry out in vitro.

The induction of DNA synthesis in the chick red cell nucleus in heterokaryons during the first cell cycle after fusion with HeLa cells

1975 ◽  
Vol 18 (3) ◽  
pp. 455-490
Author(s):  
R.T. Johnson ◽  
A.M. Mullinger
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Hela Cells ◽  
S Phase ◽  
Red Cells ◽  
Red Cell ◽  
Embryonic Chick ◽  
Cell Cycles ◽  
Phase Protein ◽  
Different Parts

Induction of DNA synthesis in embryonic chick red cells has been examined during the first and second cell cycles after fusion with HeLa cells synchronized in different parts of G1 and S-phase. The data indicate that: (i) the younger the embryonic blood the more rapidly the red cells are induced into DNA synthesis; (ii) the greater the ratio of HeLa to chick nuclei in the heterokaryon, the more rapidly the induction occurs; (iii) DNA synthesis in the chick nucleus can continue after the HeLa nucleus has left S-phase and entered either G2 or mitosis; (iv) the induction potential of late S-phase HeLa is somewhat lower than that of early or mid S-phase cells; (v) less than 10% of the chick DNA is replicated during the first cycle after fusion and only a small proportion (15%) of the chick nuclei approach the 4C value of DNA during the second cycle after fusion; (vi) the newly synthesized DNA is associated either with the condensed regions of the nucleus or with the boundaries between condensed and non-condensed regions; (vii) the chick chromosomes at the first and second mitosis after fusion are in the form of PCC prematurely condensed chromosomes); they are never fully replicated and are often fragmentary; (viii) DNA synthesis in the chick nuclei is accompanied by an influx of protein (both G1 and S-phase protein) from the HeLa component of the heterokaryon.

scholarly journals Cell cycle-dependent phosphorylation and dephosphorylation of the yeast DNA polymerase alpha-primase B subunit.

1995 ◽  
Vol 15 (2) ◽  
pp. 883-891 ◽  
Author(s):  
M Foiani ◽  
G Liberi ◽  
G Lucchini ◽  
P Plevani
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Dna Polymerase ◽  
Posttranslational Modifications ◽  
S Phase ◽  
Dna Polymerase Alpha ◽  
B Subunit ◽  
Initiation Of Dna Replication ◽  
Cycle Dependent

The yeast DNA polymerase alpha-primase B subunit functions in initiation of DNA replication. This protein is present in two forms, of 86 and 91 kDa, and the p91 polypeptide results from cell cycle-regulated phosphorylation of p86. The B subunit present in G1 arises by dephosphorylation of p91 while cells are exiting from mitosis, becomes phosphorylated in early S phase, and is competent and sufficient to initiate DNA replication. The B subunit transiently synthesized as a consequence of periodic transcription of the POL12 gene is phosphorylated no earlier than G2. Phosphorylation of the B subunit does not require execution of the CDC7-dependent step and ongoing DNA synthesis. We suggest that posttranslational modifications of the B subunit might modulate the role of DNA polymerase alpha-primase in DNA replication.

scholarly journals Aphidicolin does not inhibit DNA repair synthesis in ultraviolet-irradiated HeLa cells. A radioautographic study

1981 ◽  
Vol 199 (2) ◽  
pp. 453-455 ◽  
Author(s):  
N Hardt ◽  
G Pedrali-Noy ◽  
F Focher ◽  
S Spadari
Keyword(s):  
Dna Repair ◽  
Dna Replication ◽  
Dna Synthesis ◽  
Dna Polymerase ◽  
Hela Cells ◽  
Nuclear Dna ◽  
Detectable Effect ◽  
Repair Synthesis ◽  
Dna Polymerase Alpha ◽  
Dna Repair Synthesis

A radioautographic examination of nuclear DNA synthesis in unirradiated and u.v.-irradiated HeLa cells, in the presence and in the absence of aphidicolin, showed that aphidicolin inhibits nuclear DNA replication and has no detectable effect on DNA repair synthesis. Although the results establish that in u.v.-irradiated HeLa cells most of the DNA repair synthesis is not due to DNA polymerase alpha, they do not preclude a significant role for this enzyme in DNA repair processes.

Evidence that a critical threshold of DNA polymerase-alpha activity may be required for the initiation of DNA synthesis in mammalian cell heterokaryons

1982 ◽  
Vol 113 (1) ◽  
pp. 141-151 ◽  
Author(s):  
William R. Pendergrass ◽  
Anthony C. Saulewicz ◽  
Glenna C. Burmer ◽  
Peter S. Rabinovitch ◽  
Thomas H. Norwood ◽  
...  
Keyword(s):  
Dna Synthesis ◽  
Mammalian Cell ◽  
Dna Polymerase ◽  
Alpha Activity ◽  
Critical Threshold ◽  
Dna Polymerase Alpha

scholarly journals Mutational Effect of Fission Yeast Polα on Cell Cycle Events

1998 ◽  
Vol 9 (8) ◽  
pp. 2107-2123 ◽  
Author(s):  
Dipa Bhaumik ◽  
Teresa S.-F. Wang
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Dna Polymerase ◽  
Kinase Activity ◽  
S Phase ◽  
Catalytic Function ◽  
Physical Presence ◽  
Initiation Of Dna Replication ◽  
Mutant Cells ◽  
Mutational Effect

Polα is the principal DNA polymerase for initiation of DNA replication and also functions in postinitiation DNA synthesis. In this study, we investigated the cell cycle responses induced by mutations inpolα +. Germinating spores carrying either a deletion of polα +(polαΔ) or a structurally intact but catalytically dead polα mutation proceed to inappropriate mitosis with no DNA synthesis. This suggests that the catalytic function, and not the physical presence of Polα, is required to generate the signal that prevents the cells from entering mitosis prematurely. Cells with apolαts allele arrest the cell cycle near the hydroxyurea arrest point, but, surprisingly, polαts incdc20 (polε mutant) background arrested with a cdc phenoytpe, not a polαts-like phenotype. At 25°C, replication perturbation caused by polαts alleles induces Cds1 kinase activity and requires the checkpoint Rads, Cds1, and Rqh1, but not Chk1, to maintain cell viability. At 36°C, replication disruption caused by polαts alleles induces the phosphorylation of Chk1; however, mutant cells arrest with heterogeneous cell sizes with a population of the cells entering aberrant mitosis. Together, our results indicate that the initiation DNA structure synthesized by Polα is required to bring about the S phase to mitosis checkpoint, whereas replication defects of different severity caused by polαts mutations induce differential downstream kinase responses.

DNA polymerase alpha, a component of the replication initiation complex, is essential for the checkpoint coupling S phase to mitosis in fission yeast

1995 ◽  
Vol 108 (9) ◽  
pp. 3109-3118 ◽  
Author(s):  
G. D'Urso ◽  
B. Grallert ◽  
P. Nurse
Keyword(s):  
Dna Synthesis ◽  
Dna Polymerase ◽  
S Phase ◽  
Replication Initiation ◽  
Direct Immunofluorescence ◽  
Temperature Sensitive ◽  
Checkpoint Control ◽  
Initiation Complex ◽  
Dna Polymerase Alpha ◽  
Checkpoint Signal

Genetic analysis in the yeast Schizosaccharomyces pombe has shown that three genes cdc18, cut5, and cdt1, are essential for DNA synthesis and also for the checkpoint control that couples completion of DNA replication to the onset of mitosis. To test whether assembly of the replication initiation complex is an important element in the checkpoint control pathway we have investigated if DNA polymerase alpha (pol1), a component of the initiation complex, is essential for the S-phase checkpoint control. We show that germinating S. pombe spores disrupted for the pol1 gene enter mitosis despite defects in DNA synthesis. This is shown by monitoring septation index, DNA content, and by direct immunofluorescence of mitotic spindles using antibodies to alpha-tubulin. In addition we have isolated six temperature sensitive mutants in the pol1 gene that cause cell cycle arrest when grown at the nonpermissive temperature. Our experiments support a model in which DNA polymerase alpha, in addition to being part of the initiation complex, is required for a checkpoint signal that is activated as cells traverse START, and is essential to prevent mitosis until S phase has been completed. In contrast, proteins responsible for the elongation of DNA may not be necessary for this checkpoint signal.

scholarly journals Poly(ADP-ribose) Polymerase Activity Prevents Signaling Pathways for Cell Cycle Arrest after DNA Methylating Agent Exposure

2005 ◽  
Vol 280 (16) ◽  
pp. 15773-15785 ◽  
Author(s):  
Julie K. Horton ◽  
Donna F. Stefanick ◽  
Jana M. Naron ◽  
Padmini S. Kedar ◽  
Samuel H. Wilson
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Cell Cycle Arrest ◽  
Signaling Pathways ◽  
Dna Polymerase ◽  
S Phase ◽  
Dna Polymerase Β ◽  
Cycle Arrest ◽  
Parp Activity ◽  
Inhibition Of Dna Synthesis

Mouse fibroblasts, deficient in DNA polymerase β, are hypersensitive to monofunctional DNA methylating agents such as methyl methanesulfonate (MMS). Both wild-type and, in particular, repair-deficient DNA polymerase β null cells are highly sensitized to the cytotoxic effects of MMS by 4-amino-1,8-naphthalimide (4-AN), an inhibitor of poly(ADP-ribose) polymerase (PARP) activity. Experiments with synchronized cells suggest that exposure during S-phase of the cell cycle is required for the 4-AN effect. 4-AN elicits a similar extreme sensitization to the thymidine analog, 5-hydroxymethyl-2′-deoxyuridine, implicating the requirement for an intermediate of DNA repair. In PARP-1-expressing fibroblasts treated with a combination of MMS and 4-AN, a complete inhibition of DNA synthesis is apparent after 4 h, and by 24 h, all cells are arrested in S-phase of the cell cycle. Continuous incubation with 4-AN is required to maintain the cell cycle arrest. Caffeine, an inhibitor of the upstream checkpoint kinases ATM (ataxia telangiectasia-mutated) and ATR (ATM and Rad3-related), has no effect on the early inhibition of DNA synthesis, but cells are no longer able to maintain the block after 8 h. Instead, the addition of caffeine leads to arrest of cells in G2/M rather than S-phase after 24 h. Analysis of signaling pathways in cell extracts reveals an activation of Chk1 after treatment with MMS and 4-AN, which can be suppressed by caffeine. Our results suggest that inhibition of PARP activity results in sensitization to MMS through maintenance of an ATR and Chk1-dependent S-phase checkpoint.

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