Chromosome segregation from cell hybrids.II. Do differences in parental cell growth rates and phase times determine direction of loss?

1986 ◽  
Vol 28 (5) ◽  
pp. 735-743 ◽  
Author(s):  
Jennifer A. Marshall Graves ◽  
Jaclyn M. Wrigley
Keyword(s):  
Cell Cycle ◽  
Chromosome Segregation ◽  
Chinese Hamster ◽  
Parental Cell ◽  
S Phase ◽  
Chromosome Loss ◽  
Parent Cell ◽  
Cycle Times ◽  
Cell Hybrids ◽  
The One

The hypothesis that the direction of chromosome segregation in cell hybrids is determined by the interaction of parent cell cycles, or S-phase times, predicts that the segregant parent will always be the one with the longer cycle, or the longer S phase, and that late replicating chromosomes will be more frequently lost. We have tested this hypothesis by studying cell cycle parameters of mouse, Chinese hamster, and platypus parent cells and by observing chromosome loss and replication patterns in hybrids between them. Two types of hybrids have been studied: mouse–hamster hybrids showed gradual segregation, in one or other direction, of 10–60% chromosomes, while rodent–platypus hybrids (which could be selected under conditions optimal for either parent cell) showed rapid and extreme segregation of platypus chromosomes. We found no correlation between the direction of segregation and the relative lengths of parental cycle times, or phase times, nor between sequence of replication and frequency with which segregant chromosomes are lost. We therefore conclude that the direction and extent of segregation is not directly determined by the interaction of parental cycle or phase times.Key words: cell hybrids, chromosome loss, cell cycle, S phase.

Chromosome segregation from cell hybrids. I. The effect of parent cell ploidy on segregation from mouse – Chinese hamster hybrids

1984 ◽  
Vol 26 (5) ◽  
pp. 557-563 ◽  
Author(s):  
Jennifer A. Marshall Graves
Keyword(s):  
Chromosome Number ◽  
Chromosome Segregation ◽  
Chinese Hamster ◽  
Chromosome Loss ◽  
Parent Cell ◽  
Cell Hybrids ◽  
Parental Factor ◽  
Species Combination ◽  
Mouse Cells ◽  
Input Ratio

To determine whether the dosage of some parental factor influences the direction and extent of chromosome segregation, I have constructed hybrids between polyploid series of mouse and Chinese hamster lines. The input ratio of mouse: hamster chromosomes varied from 3.3 (in hybrids between diploid hamster and polyploid mouse cells) and 0.9 (in hybrids between polyploid hamster and near-diploid mouse cells). Mouse chromosomes were retained and hamster chromosomes were lost from all hybrids with input ratios ≥ 1.3; the extent of hamster chromosome loss increased from 25 to 60% as the proportion of mouse chromosomes was increased. Reverse segregation was observed in hybrids in which the ratio was 0.9; hybrids between polyploid hamster and diploid mouse cells retained most hamster chromosomes and lost 52% of mouse chromosomes. I conclude that the direction and extent of chromosome segregation from these hybrids depends on the dosage of some factor contained in the parent cells; because the volumes of polyploid cells are proportional to chromosome number, this factor could be chromosomal, nuclear, or cytoplasmic. Dosage differences should therefore be considered when comparing chromosome segregation from hybrids with cells of the same species combination, but which might differ in chromosome number (e.g., diploid lines and established lines), or cell volume (e.g., cells from different tissues).Key words: cell hybrids, mouse – hamster, segregation, chromosome loss, ploidy.

Chromosome segregation from cell hybrids. VII. Reverse segregation from karyoplast hybrids suggests control by cytoplasmic factors

Genome ◽  
1992 ◽  
Vol 35 (3) ◽  
pp. 537-540 ◽  
Author(s):  
Jennifer A. Marshall Graves ◽  
Iole Barbieri
Keyword(s):  
Chromosome Segregation ◽  
Human Cell ◽  
Chinese Hamster ◽  
Segregation Pattern ◽  
Chromosome Loss ◽  
Human Chromosomes ◽  
Cell Hybrids ◽  
Cytoplasmic Factors

Using human and Chinese hamster established lines as cell parents, we constructed hamster–human cell hybrids and human cell – hamster karyoplast hybrids. The cell hybrids retained one or two sets of hamster chromosomes and lost most of the human chromosomes. The karyoplast hybrids, however, retained a full set of human chromosomes and lost most of the Chinese hamster chromosomes. This reverse segregation pattern implies that cytoplasmic factors are major determinants of the direction of chromosome segregation.Key words: cell hybrids, chromosome loss, cytoplasmic factors, reverse segregation.

scholarly journals Cell-cycle kinetics and ultraviolet light survival in UV-1, a Chinese hamster ovary cell mutant defective in post-replication recovery

1982 ◽  
Vol 57 (1) ◽  
pp. 261-275
Author(s):  
A. Collins ◽  
C. Waldren
Keyword(s):  
Cell Cycle ◽  
Thymidine Incorporation ◽  
Excision Repair ◽  
Lethal Dose ◽  
Chinese Hamster ◽  
S Phase ◽  
Ovary Cell ◽  
Parent Cell ◽  
Inhibition Of Dna Synthesis ◽  
I Cells

UV-I, an ultraviolet-sensitive mutant of CHO-KI, is abnormally slow to recover from the inhibition of DNA synthesis caused by u.v. irradiation. When synchronized UV-I cells are irradiated in G1, their movement into S phase is unaltered, but thymidine incorporation is depressed (compared with that in the parent cell similarly treated). When irradiated in S phase, again incorporation is more depressed, and S phase suffers a greater delay in UV-I than in the parent cell. UV-I and its parent have similar capacities for excision repair of u.v.-induced damage inflicted in G1, and so enter S phase with similar amounts of unrepaired damage. The single-cell survival was measured after irradiation at different points in the cell cycle. The mutant and parent cells have similar values of D0 (mean lethal dose) except in mitosis, when the parent cell shows markedly greater resistance to u.v. irradiation. Dq (quasi-threshold dose) is fairly constant for the parent cell, but in UV-I it falls to a minimum in S phase. The responses of UV-I to u.v. irradiation are generally consistent with its known defect in the process of post-replication recovery, i.e. the ability to join up the abnormally small DNA fragments synthesized on a u.v.-damaged template.

scholarly journals The Role of Cdh1p in Maintaining Genomic Stability in Budding Yeast

Genetics ◽  
2003 ◽  
Vol 165 (2) ◽  
pp. 489-503 ◽  
Author(s):  
Karen E Ross ◽  
Orna Cohen-Fix
Keyword(s):  
Cell Cycle ◽  
Chromosome Segregation ◽  
Spindle Assembly Checkpoint ◽  
Chromosome Loss ◽  
Cyclin Dependent Kinase ◽  
Anaphase Promoting Complex ◽  
Growth Defects ◽  
Genes Encoding ◽  
Specificity Factor

Abstract Cdh1p, a substrate specificity factor for the cell cycle-regulated ubiquitin ligase, the anaphase-promoting complex/cyclosome (APC/C), promotes exit from mitosis by directing the degradation of a number of proteins, including the mitotic cyclins. Here we present evidence that Cdh1p activity at the M/G1 transition is important not only for mitotic exit but also for high-fidelity chromosome segregation in the subsequent cell cycle. CDH1 showed genetic interactions with MAD2 and PDS1, genes encoding components of the mitotic spindle assembly checkpoint that acts at metaphase to prevent premature chromosome segregation. Unlike cdh1Δ and mad2Δ single mutants, the mad2Δ cdh1Δ double mutant grew slowly and exhibited high rates of chromosome and plasmid loss. Simultaneous deletion of PDS1 and CDH1 caused extensive chromosome missegregation and cell death. Our data suggest that at least part of the chromosome loss can be attributed to kinetochore/spindle problems. Our data further suggest that Cdh1p and Sic1p, a Cdc28p/Clb inhibitor, have overlapping as well as nonoverlapping roles in ensuring proper chromosome segregation. The severe growth defects of both mad2Δ cdh1Δ and pds1Δ cdh1Δ strains were rescued by overexpressing Swe1p, a G2/M inhibitor of the cyclin-dependent kinase, Cdc28p/Clb. We propose that the failure to degrade cyclins at the end of mitosis leaves cdh1Δ mutant strains with abnormal Cdc28p/Clb activity that interferes with proper chromosome segregation.

Segregation of recessive phenotypes in somatic cell hybrids: role of mitotic recombination, gene inactivation, and chromosome nondisjunction

1981 ◽  
Vol 1 (4) ◽  
pp. 336-346
Author(s):  
C E Campbell ◽  
R G Worton
Keyword(s):  
Somatic Cell ◽  
Chinese Hamster ◽  
Mitotic Recombination ◽  
Chinese Hamster Cell ◽  
Gene Inactivation ◽  
Chromosome Loss ◽  
Resistance Locus ◽  
Chromosome 2 ◽  
Somatic Cell Hybrids ◽  
Cell Hybrids

Somatic cell hybrids heterozygous at the emetine resistance locus (emtr/emt+) or the chromate resistance locus (chrr/chr+) are known to segregate the recessive drug resistance phenotype at high frequency. We have examined mechanisms of segregation in Chinese hamster cell hybrids heterozygous at these two loci, both of which map to the long arm of Chinese hamster chromosome 2. To follow the fate of chromosomal arms through the segregation process, our hybrids were also heterozygous at the mtx (methotrexate resistance) locus on the short arm of chromosome 2 and carried cytogenetically marked chromosomes with either a short-arm deletion (2p-) or a long-arm addition (2q+). Karyotype and phenotype analysis of emetine- or chromate-resistant segregants from such hybrids allowed us to distinguish four potential segregation mechanisms: (i) loss of the emt+- or chr+-bearing chromosome; (ii) mitotic recombination between the centromere and the emt or chr loci, giving rise to homozygous resistant segregants; (iii) inactivation of the emt+ or chr+ alleles; and (iv) loss of the emt+- or chr+-bearing chromosome with duplication of the homologous chromosome carrying the emtr or chrr allele. Of 48 independent segregants examined, only 9 (20%) arose by simple chromosome loss. Two segregants (4%) were consistent with a gene inactivation mechanism, but because of their rarity, other mechanisms such as mutation or submicroscopic deletion could not be excluded. Twenty-one segregants (44%) arose by either mitotic recombination or chromosome loss and duplication; the two mechanisms were not distinguishable in that experiment. Finally, in hybrids allowing these two mechanisms to be distinguished, 15 segregants (31%) arose by chromosome loss and duplication, and none arose by mitotic recombination.

Morphology and behaviour of dinoflagellate chromosomes during the cell cycle and mitosis

2000 ◽  
Vol 113 (7) ◽  
pp. 1231-1239 ◽  
Author(s):  
Y. Bhaud ◽  
D. Guillebault ◽  
J. Lennon ◽  
H. Defacque ◽  
M.O. Soyer-Gobillard ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Cell Cycle ◽  
Confocal Microscopy ◽  
Nuclear Envelope ◽  
Chromosome Segregation ◽  
Morphological Changes ◽  
S Phase ◽  
Chromosome Behaviour ◽  
Double Number ◽  
Do So

The morphology and behaviour of the chromosomes of dinoflagellates during the cell cycle appear to be unique among eukaryotes. We used synchronized and aphidicolin-blocked cultures of the dinoflagellate Crypthecodinium cohnii to describe the successive morphological changes that chromosomes undergo during the cell cycle. The chromosomes in early G(1) phase appeared to be loosely condensed with numerous structures protruding toward the nucleoplasm. They condensed in late G(1), before unwinding in S phase. The chromosomes in cells in G(2) phase were tightly condensed and had a double number of arches, as visualised by electron microscopy. During prophase, chromosomes elongated and split longitudinally, into characteristic V or Y shapes. We also used confocal microscopy to show a metaphase-like alignment of the chromosomes, which has never been described in dinoflagellates. The metaphase-like nucleus appeared flattened and enlarged, and continued to do so into anaphase. Chromosome segregation occurred via binding to the nuclear envelope surrounding the cytoplasmic channels and microtubule bundles. Our findings are summarized in a model of chromosome behaviour during the cell cycle.

Cloning of a human S-phase cell cycle gene: use of transient expression for screening

1987 ◽  
Vol 7 (2) ◽  
pp. 775-779
Author(s):  
A Fainsod ◽  
G Diamond ◽  
M Marcus ◽  
F H Ruddle
Keyword(s):  
Cell Cycle ◽  
Genomic Library ◽  
Chinese Hamster ◽  
Chinese Hamster Cell ◽  
S Phase ◽  
Phase Cell ◽  
Cell Cycle Gene ◽  
Temperature Sensitive ◽  
Specific Cell ◽  
Restrictive Temperature

We report here the cloning of a human cell cycle gene capable of complementing a temperature-sensitive (ts) S-phase cell cycle mutation in a Chinese hamster cell line. Cloning was performed as follows. A human genomic library in phage lambda containing 600,000 phages was screened with labeled cDNA synthesized from an mRNA fraction enriched for the specific cell cycle gene message. Plaques containing DNA inserts which hybridized to the cDNA were picked, and their DNAs were assayed for transient complementation in DNA transformation experiments. The transient complementation assay we developed is suitable for most cell cycle genes and indeed for many genes whose products are required for cell proliferation. Of 845 phages screened, 1 contained an insert active in transient complementation of the ts cell cycle mutation. Introduction of this phage into the ts cell cycle mutant also gave rise to stable transformants which grew normally at the restrictive temperature for the ts mutant cells.

scholarly journals The Human Cytomegalovirus UL82 Gene Product (pp71) Accelerates Progression through the G1 Phase of the Cell Cycle

2003 ◽  
Vol 77 (6) ◽  
pp. 3451-3459 ◽  
Author(s):  
Robert F. Kalejta ◽  
Thomas Shenk
Keyword(s):  
Cell Cycle ◽  
Human Cytomegalovirus ◽  
Cell Cycle Progression ◽  
Protein Product ◽  
S Phase ◽  
Quiescent Cells ◽  
A Cell ◽  
Infected Cells ◽  
The One ◽  
Infectious Cycle

ABSTRACT As viruses are reliant upon their host cell to serve as proper environments for their replication, many have evolved mechanisms to alter intracellular conditions to suit their own needs. For example, human cytomegalovirus induces quiescent cells to enter the cell cycle and then arrests them in late G1, before they enter the S phase, a cell cycle compartment that is presumably favorable for viral replication. Here we show that the protein product of the human cytomegalovirus UL82 gene, pp71, can accelerate the movement of cells through the G1 phase of the cell cycle. This activity would help infected cells reach the late G1 arrest point sooner and thus may stimulate the infectious cycle. pp71 also induces DNA synthesis in quiescent cells, but a pp71 mutant protein that is unable to induce quiescent cells to enter the cell cycle still retains the ability to accelerate the G1 phase. Thus, the mechanism through which pp71 accelerates G1 cell cycle progression appears to be distinct from the one that it employs to induce quiescent cells to exit G0 and subsequently enter the S phase.

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