Search results for "Mitosis"
showing 10 items of 156 documents
Microtubules and the First Cell Cycle in Cultured Mesophyll Protoplasts of Nicotiana
1990
When a protoplast is excised and cultured in vitro, an organized pattern of cell divisions must be reestablished to permit organogenesis, including plant regeneration. However, in a number of species protoplasts have proved to be very recalcitrant with regard to cell division and/or plant regeneration. In an attempt to find means to overcome the regeneration problem in recalcitrant species we are investigating the processes leading to cell division and morphogenesis in mesophyll protoplasts of the model system Nicotiana. Of particular interest are the initiation of the cell cycle and the coordination of progress through the cycles as a prerequisite for subsequent morphogenesis. Mesophyll pr…
Three-dimensional structure of the anaphase-promoting complex.
2001
The anaphase-promoting complex (APC) is a cell cycle-regulated ubiquitin-protein ligase, composed of at least 11 subunits, that controls progression through mitosis and G1. Using cryo-electron microscopy and angular reconstitution, we have obtained a three-dimensional model of the human APC at a resolution of 24 A. The APC has a complex asymmetric structure 140 A x 140 A x 135 A in size, in which an outer protein wall surrounds a large inner cavity. We discuss the possibility that this cavity represents a reaction chamber in which ubiquitination reactions take place, analogous to the inner cavities formed by other protein machines such as the 26S proteasome and chaperone complexes. This cag…
Pterostilbene-induced tumor cytotoxicity: a lysosomal membrane permeabilization-dependent mechanism.
2012
The phenolic phytoalexin resveratrol is well known for its health-promoting and anticancer properties. Its potential benefits are, however, limited due to its low bioavailability. Pterostilbene, a natural dimethoxylated analog of resveratrol, presents higher anticancer activity than resveratrol. The mechanisms by which this polyphenol acts against cancer cells are, however, unclear. Here, we show that pterostilbene effectively inhibits cancer cell growth and stimulates apoptosis and autophagosome accumulation in cancer cells of various origins. However, these mechanisms are not determinant in cell demise. Pterostilbene promotes cancer cell death via a mechanism involving lysosomal membrane …
CD40 ligation protects bronchial epithelium against oxidant-induced caspase-independent cell death.
2006
KEYWORDS CLASSIFICATION: 7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide;Antigens,CD40;Apoptosis;Bronchi;cytology;Caspases;Cell Cycle;Cell Death;Cell Line,Transformed;Cell Survival;Cell Transformation,Viral;Cytoprotection;drug effects;Epithelial Cells;Humans;Italy;mechanisms of carcinogenesis;metabolism;Oxidants;pharmacology;physiology;Research;Simian virus 40;toxicity;Transcription Factor AP-1. CD40 and its ligand regulate pleiotropic biological responses, including cell proliferation, differentiation, and apoptosis. In many inflammatory lung diseases, tissue damage by environmental or endogenous oxidants plays a major role in disease pathogenesis. As the epithelial barrier is a major t…
p38α deficiency and oxidative stress cause cytokinesis failure in hepatocytes.
2015
Cytokinesis is the last step in mitosis and it implies re-organization of the actin cytoskeleton. Its failure is one of the major mechanisms of polyploidy and binucleation in mammals. Our aims were 1) to assess the role of redox-sensitive p38α MAPK in cytokinesis by studying the liver of wild type mice or liver-specific p38α knock-out mice; 2) to assess the role of oxidative stress associated with hepatocyte isolation on cytokinesis. When p38α was down-regulated in hepatocytes, MK2 phosphorylation on threonine 334 was completely abrogated. Activation of MNK-1, required for abscission of the intercellular bridge, was diminished. Key proteins of the RhoA pathway (phospho-PRK2, nuclear phospho…
Connecting temporal identity to mitosis: the regulation of Hunchback in Drosophila neuroblast lineages.
2006
Both in vertebrates and invertebrates, neural stem cells generate different cell types at different times during development. It has been suggested that this process depends on temporal identity transitions of neural progenitors, but the underlying mechanism has not been resolved, yet. Recently, Drosophila neuroblasts (NBs) have been shown to be an excellent model system to investigate this subject. Here, changes in temporal identity are regulated by sequential and transient expression of transcription factors in the NB, such as Hunchback (Hb) and Kruppel (Kr). The temporal expression profile is maintained in the progeny. Hb is expressed first and thus defines the earliest identity in a giv…
Functional distinction between Cln1p and Cln2p cyclins in the control of the Saccharomyces cerevisiae mitotic cycle.
2004
Abstract Cln1p and Cln2p are considered as equivalent cyclins on the basis of sequence homology, regulation, and functional studies. Here we describe a functional distinction between the Cln1p and Cln2p cyclins in the control of the G1/S transition. Inactivation of CLN2, but not of CLN1, leads to a larger-than-normal cell size, whereas overexpression of CLN2, but not of CLN1, results in smaller-than-normal cells. Furthermore, mild ectopic expression of CLN2, but not of CLN1, suppresses the lethality of swi4swi6 and cdc28 mutant strains. In the absence of Cln1p, the kinetics of budding, initiation of DNA replication, and activation of the Start-transcription program are not affected; by cont…
DNA damage causes TP53-dependent coupling of self-renewal and senescence pathways in embryonal carcinoma cells.
2013
Recent studies have highlighted an apparently paradoxical link between self-renewal and senescence triggered by DNA damage in certain cell types. In addition, the finding that TP53 can suppress senescence has caused a re-evaluation of its functional role in regulating these outcomes. To investigate these phenomena and their relationship to pluripotency and senescence, we examined the response of the TP53-competent embryonal carcinoma (EC) cell line PA-1 to etoposide-induced DNA damage. Nuclear POU5F1/OCT4A and P21CIP1 were upregulated in the same cells following etoposide-induced G 2M arrest. However, while accumulating in the karyosol, the amount of OCT4A was reduced in the chromatin fract…
The role of telomeres and telomerase in the senescence of postmitotic cells
2020
Senescence is a process related to the stopping of divisions and changes leading the cell to the SASP phenotype. Permanent senescence of many SASP cells contributes to faster aging of the body and development of age-related diseases due to the release of pro-inflammatory factors. Both mitotically active and non-dividing cells can undergo senescence as a result of activation of different molecular pathways. Telomeres, referred to as the molecular clock, direct the dividing cell into the aging pathway when reaching a critical length. In turn, the senescence of postmitotic cells depends not on the length of telomeres, but their functionality. Dysfunctional telomeres are responsible for trigger…
Rat CNS neurons are not yet programmed to shorten their chromatin repeat length at the end of fetal neurogenesis.
1986
Neurons from rat fetal cerebral hemispheres were grown in a synthetic medium (Maat medium), as previously described, for different periods of time. The repeat length of their chromatin was determined by micrococcal nuclease digestion and compared with that of neurons isolated from postnatal rat brain of corresponding ages. In contrast to the in vivo situation, we found that neurons, dissociated at the 16th gestational day and cultured in vitro, did not undergo the shortening of their chromatin repeat, thus indicating that, at the end of their mitotic cycles, they are not yet programmed to this event. © 1986.