Paternal chromosome loss and metabolic crisis contribute to hybrid inviability in Xenopus

Abstract Spontaneous and double-strand break (DSB)-induced allelic recombination in yeast was investigated in crosses between ura3 heteroalleles inactivated by an HO site and a +1 frameshift mutation, with flanking markers defining a 3.4-kbp interval. In some crosses, nine additional phenotypically silent RFLP mutations were present at ∼100-bp intervals. Increasing heterology from 0.2 to 1% in this interval reduced spontaneous, but not DSB-induced, recombination. For DSB-induced events, 75% were continuous tract gene conversions without a crossover in this interval; discontinuous tracts and conversions associated with a crossover each comprised ∼7% of events, and 10% also converted markers in unbroken alleles. Loss of heterozygosity was seen for all markers centromere distal to the HO site in 50% of products; such loss could reflect gene conversion, break-induced replication, chromosome loss, or G2 crossovers. Using telomere-marked strains we determined that nearly all allelic DSB repair occurs by gene conversion. We further show that most allelic conversion results from mismatch repair of heteroduplex DNA. Interestingly, markers shared between the sparsely and densely marked interval converted at higher rates in the densely marked interval. Thus, the extra markers increased gene conversion tract lengths, which may reflect mismatch repair-induced recombination, or a shift from restoration- to conversion-type repair.

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The Role of Cdh1p in Maintaining Genomic Stability in Budding Yeast

Genetics ◽

10.1093/genetics/165.2.489 ◽

2003 ◽

Vol 165 (2) ◽

pp. 489-503 ◽

Cited By ~ 1

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.

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Mutational Analysis of the Drosophila Sister-Chromatid Cohesion Protein ORD and Its Role in the Maintenance of Centromeric Cohesion

Genetics ◽

10.1093/genetics/146.4.1319 ◽

1997 ◽

Vol 146 (4) ◽

pp. 1319-1331 ◽

Cited By ~ 1

Author(s):

Sharon E Bickel ◽

Dudley W Wyman ◽

Terry L Orr-Weaver

Keyword(s):

Sister Chromatid ◽

Mutational Analysis ◽

Germ Line ◽

Sister Chromatid Cohesion ◽

Chromosome Loss ◽

Male And Female ◽

Chromatid Cohesion ◽

Random Segregation ◽

Kinetochore Function ◽

Segregation Of Chromosomes

The ord gene is required for proper segregation of all chromosomes in both male and female Drosophila meiosis. Here we describe the isolation of a null ord allele and examine the consequences of ablating ord function. Cytologically, meiotic sister-chromatid cohesion is severely disrupted in flies lacking ORD protein. Moreover, the frequency of missegregation in genetic tests is consistent with random segregation of chromosomes through both meiotic divisions, suggesting that sister cohesion may be completely abolished. However, only a slight decrease in viability is observed for ord null flies, indicating that ORD function is not essential for cohesion during somatic mitosis. In addition, we do not observe perturbation of germ-line mitotic divisions in flies lacking ORD activity. Our analysis of weaker ord alleles suggests that ORD is required for proper centromeric cohesion after arm cohesion is released at the metaphase I/anaphase I transition. Finally, although meiotic cohesion is abolished in the ord null fly, chromosome loss is not appreciable. Therefore, ORD activity appears to promote centromeric cohesion during meiosis II but is not essential for kinetochore function during anaphase.

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ALTERED FIDELITY OF MITOTIC CHROMOSOME TRANSMISSION IN CELL CYCLE MUTANTS OF S. CEREVISIAE

Genetics ◽

10.1093/genetics/110.3.381 ◽

1985 ◽

Vol 110 (3) ◽

pp. 381-395

Author(s):

Leland H Hartwell ◽

David Smith

Keyword(s):

Cell Cycle ◽

Gene Product ◽

Mitotic Chromosome ◽

Mitotic Recombination ◽

Chromosome Loss ◽

Temperature Sensitive ◽

Repair Pathway ◽

Dna Metabolism ◽

Temperature Sensitive Mutants ◽

Chromosome Transmission

ABSTRACT Thirteen of 14 temperature-sensitive mutants deficient in successive steps of mitotic chromosome transmission (cdc2, 4, 5, 6, 7, 8, 9, 13, 14, 15, 16, 17 and 20) from spindle pole body separation to a late stage of nuclear division exhibited a dramatic increase in the frequency of chromosome loss and/or mitotic recombination when they were grown at their maximum permissive temperatures. The increase in chromosome loss and/or recombination is likely to be due to the deficiency of functional gene product rather than to an aberrant function of the mutant gene product since the mutant alleles are, with one exception, recessive to the wild-type allele for this phenotype. The generality of this result suggests that a delay in almost any stage of chromosome replication or segregation leads to a decrease in the fidelity of mitotic chromosome transmission. In contrast, temperature-sensitive mutants defective in the control step of the cell cycle (cdc28), in cytokinesis (cdc3) or in protein synthesis (ils1) did not exhibit increased recombination or chromosome loss.—Based upon previous results with mutants and DNA-damaging agents in a variety of organisms, we suggest that the induction of mitotic recombination in certain mutants is due to the action of a repair pathway upon nicks or gaps left in the DNA. This interpretation is supported by the fact that the induced recombination is dependent upon the RAD52 gene product, an essential component in the recombinogenic DNA repair pathway. Gene products whose deficiency leads to induced recombination are, therefore, strong candidates for proteins that function in DNA metabolism. Among the mutants that induce recombination are those known to be defective in some aspect of DNA replication (cdc2, 6, 8, 9) as well as some mutants defective in the G2 (cdc13 and 17) and M (cdc5 and 14) phases of the mitotic cycle. We suggest that special aspects of DNA metabolism may be occurring in G2 and M in order to prepare the chromosomes for proper segregation.

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Cytogenetic Findings in Primary Non-Small Cell Lung Cancer

Tumori Journal ◽

10.1177/030089169408000214 ◽

1994 ◽

Vol 80 (2) ◽

pp. 151-156

Author(s):

Elvira D'Alessandro ◽

Maria Luisa Lo Re ◽

Roberto Crisci ◽

Claudio Ligas ◽

Giorgio Furio Coloni

Keyword(s):

Lung Cancer ◽

Small Cell Lung Cancer ◽

Cell Lung Cancer ◽

Small Cell ◽

Chromosome Loss ◽

Small Cell Lung ◽

Primary Nsclc ◽

Cytogenetic Analyses ◽

Triploid Clone

Non-small cell lung cancer (NSCLC) shows a complex cytogenetic heterogeneity and up to now no particular chromosomal aberration seems to characterize its malignant evolution. We therefore performed cytogenetic analyses of 20 primary NSCLC, 8 adenocarcinomas and 12 squamous cell carcinomas on direct preparations or short-term cultures. Only 1 case was analyzed after long-term culture. Results were obtained from 11 samples and clonal rearrangements were found in 3 cases, a diploid and a near-triploid clone with several aberrations such as i (9q), rob (14; 15) and rob (21; 21) in 1 case, a near-triploid clone in 1 case, and Y chromosome loss in 1 case. Other aberrations found were sporadic, but + 7 aneuploidy and translocations involving 1p were detected in 2 and 3 samples respectively. Although to date it has been very difficult to recognize primary changes in NSCLC, nevertheless a literature review and our results indicate that i(9q) and robertsonian translocations are relevant findings.

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