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Metaphase

About: Metaphase is a research topic. Over the lifetime, 6925 publications have been published within this topic receiving 291590 citations. The topic is also known as: GO:0007091 & mitotic metaphase/anaphase transition.


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Journal ArticleDOI
TL;DR: In late metaphase, when all kinetochores are attached to spindle microtubules and the spindle assembly checkpoint is satisfied, Nup98 and Rae1 are released from these complexes, thereby allowing for prompt ubiquitination of securin by APC/CCdh1.
Abstract: Orderly progression through mitosis is regulated by the anaphase-promoting complex/cyclosome (APC/C), a large multiprotein E3 ubiquitin ligase that targets key mitotic regulators for destruction by the proteasome. APC/C has two activating subunits, Cdc20 and Cdh1. The well-established view is that Cdc20 activates APC/C from the onset of mitosis through the metaphase-anaphase transition, and that Cdh1 does so from anaphase through G1. Recent work, however, indicates that Cdh1 also activates APC/C in early mitosis and that this APC/C pool targets the anaphase inhibitor securin. To prevent premature degradation of securin, the nuclear transport factors Nup98 and Rae1 associate with APC/C(Cdh1)-securin complexes. In late metaphase, when all kinetochores are attached to spindle microtubules and the spindle assembly checkpoint is satisfied, Nup98 and Rae1 are released from these complexes, thereby allowing for prompt ubiquitination of securin by APC/C(Cdh1). This, and other mechanisms by which the catalytic activity of APC/C is tightly regulated to ensure proper timing of degradation of each of its mitotic substrates, are highlighted.

102 citations

Journal ArticleDOI
TL;DR: The regularly occurring secondary constrictions on metaphase chromosomes of mammalian cells prove to be nucleolus organizers as expected, and electron micrographs of the organizer region show that the nucleolu organizer at metaphase is not a constriction.
Abstract: The regularly occurring secondary constrictions on metaphase chromosomes of mammalian cells prove to be nucleolus organizers as expected The expression of nucleolus organizers as secondary constrictions, however, varies from cell to cell and from tissue to tissue, including cultivation in vitro Electron micrographs of the organizer region show that the nucleolus organizer at metaphase is not a constriction The width of the organizer area is the same as the condensed chromosomal arms; but the filaments, which are the major components of this region, show a diameter of 50–70 A The condensed chromosome arms consist of filaments 150–200 A in diameter In some mammalian species, structures similar to the nucleolus organizer are located at the end of chromosomes These may be terminal nucleolus organizers

102 citations

Journal ArticleDOI
TL;DR: The function of Siah1a during mammalian development is analyzed to reveal novel roles in growth, viability, and fertility and suggests that Siah 1a may be part of a novel E3 complex acting late in the first meiotic division.
Abstract: The mammalian Siah genes encode highly conserved proteins containing a RING domain. As components of E3 ubiquitin ligase complexes, Siah proteins facilitate the ubiquitination and degradation of diverse protein partners including beta-catenin, N-CoR, and DCC. We used gene targeting in mice to analyze the function of Siah1a during mammalian development and reveal novel roles in growth, viability, and fertility. Mutant animals have normal weights at term but are postnatally growth retarded, despite normal levels of pituitary growth hormone. Embryonic fibroblasts isolated from mutant animals grow normally. Most animals die before weaning, and few survive beyond 3 months. Serum gonadotropin levels are normal in Siah1a mutant mice; however, females are subfertile and males are sterile due to a block in spermatogenesis. Although spermatocytes in mutant mice display normal meiotic prophase and meiosis I spindle formation, they accumulate at metaphase to telophase of meiosis I and subsequently undergo apoptosis. The requirement of Siah1a for normal progression beyond metaphase I suggests that Siah1a may be part of a novel E3 complex acting late in the first meiotic division.

102 citations

Journal Article
TL;DR: Flow cytometric techniques developed to assay lymphocyte stimulation as reflected by the increase in the cell transcriptional activity and cell progression through the cell cycle may also prove to be useful in recognizing and quantitating noncycling cells in other cell systems.
Abstract: Flow cytometric techniques have been developed to assay lymphocyte stimulation as reflected by the increase in the cell transcriptional activity and cell progression through the cell cycle. The metachromatic fluorescent dye, acridine orange, is used to (a) stain DNA and RNA differentially in individual cells, and (b) stain nuclear chromatin after removal of cellular RNA BY RNase and cell pretreatment at acidic pH. Stimulated cells with diploid DNA content (G1) have an increased content of stainable RNA that makes it possible to distinguish them from nonstimulated (G0) cells. G0 cells can also be distinguished from G1 cells based on differences in stainability of their nuclear chromatin after treatment with acid. Mitotic indices can be scored automatically, inasmuch as the metaphase chromatin stains differently than does chromatin in the interphase cells. Altogether, the numbers of cells in the G0, G1, S, G2, and M phases may be obtained rapidly and with great accuracy. The cell transciptional activity can be correlated with changes in nuclear chromatin (e.g., during the transition from G0 to G1). The two independent techniques may also prove to be useful in recognizing and quantitating noncycling cells in other cell systems. The possible mechanisms responsible for differential stainability of nuclear chromatin in cells at different phases of the cell cycle are discussed.

102 citations

Journal ArticleDOI
TL;DR: Improved techniques for fluorescence in situ hybridisation and the amplification and labelling of sorted chromosomes using degenerate oligonucleotide-primed PCR have led to the widespread use of chromosome painting both for the resolution of complex chromosome aberrations and for the study of karyotype evolution by cross-species reciprocal chromosome painting.
Abstract: Chromosome sorting from fluid suspensions of metaphase chromosomes using a fluorescence-activated cell sorter has been used for a number of years to produce chromosome-specific genomic libraries and other reagents for chromosome mapping. Improved techniques for fluorescence in situ hybridisation and the amplification and labelling of sorted chromosomes using degenerate oligonucleotide-primed PCR have led to the widespread use of chromosome painting both for the resolution of complex chromosome aberrations and for the study of karyotype evolution by cross-species reciprocal chromosome painting. The chromosomes of a large number of different species have been sorted and used to make chromosome-specific paints and already new data challenging results of earlier phylogenetic studies have been obtained. Sorted chromosomes provide the resource for multicolour chromosome analysis of all chromosomes simultaneously. Such reagents are now available for all human and mouse chromosomes and are proving particularly useful in the analysis of cancer chromosomes.

102 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202373
2022116
202182
202087
2019113
201888