scholarly journals Topoisomerase inhibitors can selectively interfere with different stages of simian virus 40 DNA replication.

1986 ◽  
Vol 6 (12) ◽  
pp. 4221-4227 ◽  
Author(s):  
R M Snapka
Keyword(s):  
Dna Replication ◽  
Sister Chromatid ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Sister Chromatid Exchanges ◽  
Replication Forks ◽  
Dna Breaks ◽  
Rapid Reversal ◽  
Chromatid Exchanges

I have found that antineoplastic drugs which are known to be inhibitors of mammalian DNA topoisomerases have pronounced and selective effects on simian virus 40 DNA replication. Ellipticine, 4'-(9-acridinylamino)methanesulfon-m-aniside, and Adriamycin blocked decatenation of newly replicated simian virus 40 daughter chromosomes in vivo. The arrested decatenation intermediates produced by these drugs contained single-strand DNA breaks. Ellipticine in particular produced these catenated dimers rapidly and efficiently. Removal of the drug resulted in rapid reversal of the block and completion of decatenation. The demonstration that these drugs interfere with decatenation suggests that they may exert their cytotoxic and antineoplastic effects by preventing the separation of newly replicated cellular chromosomes. Camptothecin rapidly breaks replication forks in growing Cairns structures. It is likely that the target of camptothecin is the "swivel" topoisomerase required for DNA replication and that it is located at or very near the replication fork in vivo. Evidence is presented that many of the broken Cairns structures are in fact half-completed sister chromatid exchanges. One pathway for the resolution of these structures is completion of the sister chromatid exchange to produce a circular head-to-tail dimer.

Topoisomerase inhibitors can selectively interfere with different stages of simian virus 40 DNA replication

1986 ◽  
Vol 6 (12) ◽  
pp. 4221-4227
Author(s):  
R M Snapka
Keyword(s):  
Dna Replication ◽  
Sister Chromatid ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Sister Chromatid Exchanges ◽  
Replication Forks ◽  
Dna Breaks ◽  
Rapid Reversal ◽  
Chromatid Exchanges

I have found that antineoplastic drugs which are known to be inhibitors of mammalian DNA topoisomerases have pronounced and selective effects on simian virus 40 DNA replication. Ellipticine, 4'-(9-acridinylamino)methanesulfon-m-aniside, and Adriamycin blocked decatenation of newly replicated simian virus 40 daughter chromosomes in vivo. The arrested decatenation intermediates produced by these drugs contained single-strand DNA breaks. Ellipticine in particular produced these catenated dimers rapidly and efficiently. Removal of the drug resulted in rapid reversal of the block and completion of decatenation. The demonstration that these drugs interfere with decatenation suggests that they may exert their cytotoxic and antineoplastic effects by preventing the separation of newly replicated cellular chromosomes. Camptothecin rapidly breaks replication forks in growing Cairns structures. It is likely that the target of camptothecin is the "swivel" topoisomerase required for DNA replication and that it is located at or very near the replication fork in vivo. Evidence is presented that many of the broken Cairns structures are in fact half-completed sister chromatid exchanges. One pathway for the resolution of these structures is completion of the sister chromatid exchange to produce a circular head-to-tail dimer.

scholarly journals PRESENCE OF A BASE LINE LEVEL OF SISTER CHROMATID EXCHANGES IN SOMATIC CELLS OF DROSOPHILA MELANOGASTER IN VIVO AND IN VITRO

Genetics ◽  
1982 ◽  
Vol 100 (2) ◽  
pp. 259-278
Author(s):  
Hideo Tsuji
Keyword(s):  
Drosophila Melanogaster ◽  
Sister Chromatid ◽  
Ganglion Cells ◽  
Sister Chromatid Exchanges ◽  
Base Line ◽  
Cell Cycles ◽  
Chromatid Exchanges ◽  
Third Instar Larvae

ABSTRACT Sister chromatid exchanges (SCEs) under in vivo and in vitro conditions were examined in ganglion cells of third-instar larvae of Drosophila melanogaster (Oregon-R). In the in vivo experiment, third-instar larvae were fed on synthetic media containing 5-bromo-2′-deoxyuridine (BrdUrd). After two cell cycles, ganglia were dissected and treated with colchicine. In the in vitro experiment, the ganglia were also incubated in media containing BrdUrd for two cell cycles, and treated with colchicine. SCEs were scored in metaphase stained with Hoechst 33258 plus Giemsa. The frequencies of SCEs stayed constant in the range of 25-150 vg/ml and 0.25-2.5 vg/ml of BrdUrd in vivo and in vitro, respectively. SCEs gradually increased at higher concentrations, strongly suggesting that at least a fraction of the detected SCEs are spontaneous. The constant levels of SCE frequency were estimated, on the average, at 0.103 per cell per two cell cycles for females and 0.101 for males in vivo and at 0.096 for females and 0.091 for males in vitro. No difference was found in the SCE frequency between sexes at any of the BrdUrd concentrations. The analysis for the distribution of SCEs within chromosomes revealed an extraordinarily high proportion of the SCEs at the junctions between euchromatin and heterochromatin; the remaining SCEs were preferentially localized in the euchromatic regions of the chromosomes and in the heterochromatic Y chromosome. These results were largely inconsistent with those of Gatti et al. (1979).

Distribution of sister chromatid exchanges on the mouse chromosomes in vivo with reference to the replication properties of the X chromosome

1984 ◽  
Vol 26 (2) ◽  
pp. 152-157
Author(s):  
S. M. Singh ◽  
D. L. Reimer
Keyword(s):  
Bone Marrow ◽  
X Chromosome ◽  
Sister Chromatid ◽  
Bone Marrow Cells ◽  
Relative Length ◽  
Chromosome Length ◽  
Sister Chromatid Exchanges ◽  
Chromatid Exchanges ◽  
Marrow Cells

Frequency of sister chromatid exchanges (SCE) were recorded separately for different chromosomes from bone marrow cells of female mice of the two genetic strains (C3H/S and C57BL/6J). SCEs were evaluated following different doses of 5-bromo-2′deoxyuridine (BrdU) as nine hourly i.p. injections. The SCE per cell increased with increasing BrdU doses which was slightly higher in C3H/S than in the C57BL/6J. SCEs per cell were variable at every treatment – strain combination, possibly reflecting the heterogeneous nature of the bone marrow cells. In general, there is a positive correlation between SCE per chromosome and the relative chromosome length. Total SCEs on one of the large chromosomes (most likely the X chromosome), however, are significantly higher than expected on the basis of relative length alone. Most of this increase is attributable to one of the homologues of this chromosome, which is not in synchrony with the rest of the chromosomes and may represent the late-replicating X. These results when viewed in the light of replication properties of the heterochromatinized X, suggest a direct involvement of DNA replication in SCE formation and may argue against the replication point as the sole site for the SCEs.Key words: sister chromatid exchange, BrdU, recombination, replication, X chromosome.

Induction of Sister Chromatid Exchanges with Gossypol Acetate in Mouse Spermatogonial Cells In Vivo

1984 ◽  
pp. 817-818
Author(s):  
R. L. Wang ◽  
M. M. Wang ◽  
Q. Lu ◽  
H. Z. Zhing ◽  
Y. L. Yao ◽  
...  
Keyword(s):  
Sister Chromatid ◽  
Sister Chromatid Exchanges ◽  
Chromatid Exchanges

Method of mapping DNA replication origins

1985 ◽  
Vol 5 (1) ◽  
pp. 85-92
Author(s):  
L D Spotila ◽  
J A Huberman
Keyword(s):  
Dna Replication ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Replication Forks ◽  
Replication Origins ◽  
Chromosomal Dna ◽  
Dna Restriction Fragments ◽  
Dna Restriction ◽  
Dna Replication Origins

We have developed a method which allows determination of the direction in which replication forks move through segments of chromosomal DNA for which cloned probes are available. The method is based on the facts that DNA restriction fragments containing replication forks migrate more slowly through agarose gels than do non-fork-containing fragments and that the extent of retardation of the fork-containing fragments is a function of the extent of replication. The procedure allows the identification of DNA replication origins as sites from which replication forks diverge. In this paper we demonstrate the feasibility of this procedure, with simian virus 40 DNA as a model, and we discuss its applicability to other systems.

scholarly journals Absence of BLM leads to accumulation of chromosomal DNA breaks during both unperturbed and disrupted S phases

2004 ◽  
Vol 165 (6) ◽  
pp. 801-812 ◽  
Author(s):  
Wenhui Li ◽  
Soo-Mi Kim ◽  
Joon Lee ◽  
William G. Dunphy
Keyword(s):  
Dna Replication ◽  
Chromosomal Abnormalities ◽  
Sister Chromatid Exchanges ◽  
Chromosomal Dna ◽  
Dna Breaks ◽  
Egg Extracts ◽  
Xenopus Egg ◽  
Xenopus Egg Extracts ◽  
Chromatid Exchanges ◽  
Chromosomal Defects

Bloom's syndrome (BS), a disorder associated with genomic instability and cancer predisposition, results from defects in the Bloom's helicase (BLM) protein. In BS cells, chromosomal abnormalities such as sister chromatid exchanges occur at highly elevated rates. Using Xenopus egg extracts, we have studied Xenopus BLM (Xblm) during both unperturbed and disrupted DNA replication cycles. Xblm binds to replicating chromatin and becomes highly phosphorylated in the presence of DNA replication blocks. This phosphorylation depends on Xenopus ATR (Xatr) and Xenopus Rad17 (Xrad17), but not Claspin. Xblm and Xenopus topoisomerase IIIα (Xtop3α) interact in a regulated manner and associate with replicating chromatin interdependently. Immunodepletion of Xblm from egg extracts results in accumulation of chromosomal DNA breaks during both normal and perturbed DNA replication cycles. Disruption of the interaction between Xblm and Xtop3α has similar effects. The occurrence of DNA damage in the absence of Xblm, even without any exogenous insult to the DNA, may help to explain the genesis of chromosomal defects in BS cells.

Sign in / Sign up

Export Citation Format

Share Document