Search results for "Mitosis"
showing 10 items of 156 documents
Methylation Reprogramming and Chromosomal Aneuploidy in In Vivo Fertilized and Cloned Rabbit Preimplantation Embryos1
2004
Active demethylation of the paternal genome but not of the maternal genome occurs in fertilized mouse, rat, pig, and bovine zygotes. To study whether this early demethylation wave is important for embryonic development, we have analyzed the global methylation patterns of both in vivo-fertilized and cloned rabbit embryos. Anti-5-methylcytosine immunofluorescence of in vivo-fertilized rabbit embryos revealed that the equally high methylation levels of the paternal and maternal genomes are largely maintained from the zygote up to the 16-cell stage. The lack of detectable methylation changes in rabbit preimplantation embryos suggests that genome-wide demethylation is not an obligatory requireme…
Expression of the kinetochore protein Hec1 during the cell cycle in normal and cancer cells and its regulation by the pRb pathway.
2010
Highly Expressed in Cancer protein 1 (Hec1) is a subunit of the Ndc80 complex, a constituent of the mitotic kinetochore. HEC1 has been shown to be overexpressed in many cancers, suggesting that HEC1 upregulation is involved in the generation and/or maintenance of the tumour phenotype. However, the regulation of Hec1 expression in normal and tumour cells and the molecular alterations promoting accumulation of this protein in cancer cells are still unknown. Here we show that elevated Hec1 protein levels are characteristic of transformed cell lines of different origins and that kinetochore recruitment of this protein is also increased in cancer cell lines in comparison with normal human cells.…
Nuclear and Cytoplasmic Survivin: Molecular Mechanism, Prognostic, and Therapeutic Potential.
2007
Abstract Survivin's proposed dual role as an apoptosis inhibitor and a mitotic effector positioned it in the front line of cancer research. Notably, survivin is detected as a cytoplasmic and nuclear protein in cancer patients, which stimulated numerous studies to investigate and to speculate on the functional and prognostic significance of its dynamic localization. Recent evidence shows that the direct interaction of survivin with the nuclear export receptor Crm1 is critically involved in its intracellular localization and cancer-relevant functions. Here, we review our current understanding of the Crm1/survivin interface and discuss its potential prognostic and therapeutic relevance. [Cance…
Transformation of Aspergillus parasiticus using autonomously replicating plasmids from Aspergillus nidulans.
1994
A genetic transformation system for the aflatoxin-producing fungus Aspergillus parasiticus using two autonomously replicating plasmids from A. nidulans (ARp1 and pDHG25) is reported. Transformation frequencies using the plasmid pDHG25 were from 5 x 10(2) to 2.5 x 10(4) transformants per 10(6) viable protoplasts and microgram DNA. The stability of the plasmids in the transformants was also studied. This transformation system offers a new opportunity to clone genes related to aflatoxin production using appropriate aflatoxin-defective mutants.
Functional Inactivation of pRB Results in Aneuploid Mammalian Cells After Release From a Mitotic Block
2002
AbstractThe widespread chromosome instability observed in tumors and in early stage carcinomas suggests that aneuploidy could be a prerequisite for cellular transformation and tumor initiation. Defects in tumor suppressers and genes that are part of mitotic checkpoints are likely candidates for the aneuploid phenotype. By using flow cytometric, cytogenetic, immunocytochemistry techniques we investigated whether pRB deficiency could drive perpetual aneuploidy in normal human and mouse fibroblasts after mitotic checkpoint challenge by microtubule-destabilizing drugs. Both mouse and human pRB-deficient primary fibroblasts resulted, upon release from a mitotic block, in proliferating aneuploid …
The bacterial cytolethal distending toxin (CDT) triggers a G2 cell cycle checkpoint in mammalian cells without preliminary induction of DNA strand br…
1999
The bacterial cytolethal distending toxin (CDT) was previously shown to arrest the tumor-derived HeLa cell line in the G2-phase of the cell cycle through inactivation of CDK1, a cyclin-dependent kinase whose state of activation determines entry into mitosis. We have analysed the effects induced in HeLa cells by CDT, in comparison to those induced by etoposide, a prototype anti-tumoral agent that triggers a G2 cell cycle checkpoint by inducing DNA damage. Both CDT and etoposide inhibit cell proliferation and induces the formation of enlarged mononucleated cells blocked in G2. In both cases, CDK1 from arrested cells could be re-activated both in vitro by dephosphorylation by recombinant Cdc25…
Chromosomal instability, reproductive cell death and apoptosis induced by O6-methylguanine in Mex−, Mex+ and methylation-tolerant mismatch repair com…
1998
O6-Methylguanine (O6-MeG) is induced in DNA by methylating environmental carcinogens and various cytostatic drugs. It is repaired by O6-methylguanine-DNA methyltransferase (MGMT). If not repaired prior to replication, the lesion generates gene mutations and leads to cell death, sister chromatid exchanges (SCEs), chromosomal aberrations and malignant transformation. To address the question of how O6-MeG is transformed into genotoxic effects, isogenic Chinese hamster cell lines either not expressing MGMT (phenotypically Mex-), expressing MGMT (Mex+) or exhibiting the tolerance phenotype (Mex-, methylation resistant) were compared as to their clastogenic response. Mex- cells were more sensitiv…
Genomic instability induced by α-pinene in Chinese hamster cell line.
2012
Here, we report the effects of exposure of mammalian cells to α-pinene, a bicyclic monoterpene used in insecticides, solvents and perfumes. Morphological analysis, performed in V79-Cl3 cells exposed for 1 h to increasing concentrations (25 up to 50 μM) of α-pinene, indicated a statistically significant increase in micronucleated and multinucleated cell frequencies; apoptotic cells were seen at 40 and 50 μM. This monoterpene caused genomic instability by interfering with mitotic process; in fact, 50% of cells (versus 19% of control cells) showed irregular mitosis with multipolar or incorrectly localised spindles. Cytogenetic analysis demonstrated high-frequency hypodiploid metaphases as well…
Detection of cytokeratin dynamics by time-lapse fluorescence microscopy in living cells.
1999
To monitor the desmosome-anchored cytokeratin network in living cells fusion protein HK13-EGFP consisting of human cytokeratin 13 and the enhanced green fluorescent protein was stably expressed in vulvar carcinoma-derived A-431 cells. It is shown for A-431 subclone AK13-1 that HK13-EGFP emits strong fluorescence in fixed and living cells, being part of an extended cytoplasmic intermediate filament network that is indistinguishable from that of parent A-431 cells. Biochemical, immunological and ultrastructural analyses demonstrate that HK13-EGFP behaves identically to the endogenous cytokeratin 13 and is therefore a reliable in vivo tag for this polypeptide and the structures formed by it. T…
γ-Tubulin in Barley and Tobacco: Sequence Relationship and RNA Expression Patterns in Developing Leaves during Mitosis and Post-Mitotic Growth
2002
gamma-Tubulin is typically associated with microtubule organising centres, such as the centrosome, and appears to mediate microtubule nucleation. Centrosomes are usually not found in higher plants, but active genes homologous to gamma-tubulin have been identified in the plant kingdom, including the angiosperms Arabidopsis, maize and rice. We have isolated and characterised gamma-tubulin cDNA sequences of two further angiosperm species, barley and tobacco. Sequence comparison revealed a phylogenetic tree with distinct clusters corresponding to the systematic position of the species. Furthermore, domains, thought to be exposed in the folded protein and to be candidates for interaction with as…