Topic
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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TL;DR: It is shown that displacement of human cohesin from early mitotic chromosomes requires dissociation of Smc3 from Scc1 but no opening of the other two gates, and proposed that the use of differently regulated gates for loading and release facilitates unidirectionality of DNA's entry into and exit from the cohesIn ring.
Abstract: Faithful transmission of chromosomes during eukaryotic cell division requires sister chromatids to be paired from their generation in S phase until their separation in M phase. Cohesion is mediated by the cohesin complex, whose Smc1, Smc3 and Scc1 subunits form a tripartite ring that entraps both DNA double strands. Whereas centromeric cohesin is removed in late metaphase by Scc1 cleavage, metazoan cohesin at chromosome arms is displaced already in prophase by proteolysis-independent signalling. Which of the three gates is triggered by the prophase pathway to open has remained enigmatic. Here, we show that displacement of human cohesin from early mitotic chromosomes requires dissociation of Smc3 from Scc1 but no opening of the other two gates. In contrast, loading of human cohesin onto chromatin in telophase occurs through the Smc1–Smc3 hinge. We propose that the use of differently regulated gates for loading and release facilitates unidirectionality of DNA's entry into and exit from the cohesin ring.
118 citations
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TL;DR: To obtain optimal specific fluorescence and very low aspecific background staining, several modifications of the in situ hybridization and the immunocytochemical procedure proved to be essential for optimal results.
118 citations
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TL;DR: The results suggest that CKII may play significant roles in cell division control by shifting its localization between the cytoplasm and nucleus.
Abstract: We have developed specific antibodies to synthetic peptide antigens that react with the individual subunits of casein kinase II (CKII). Using these antibodies, we studied the localization of CKII in asynchronous HeLa cells by immunofluorescence and immunoelectron microscopy. Further studies were done on HeLa cells arrested at the G1/S transition by hydroxyurea treatment. Our results indicate that the CKII alpha and beta subunits are localized in the cytoplasm during interphase and are distributed throughout the cell during mitosis. Further electron microscopic investigation revealed that CKII alpha subunit is associated with spindle fibers during metaphase and anaphase. In contrast, the CKII alpha' subunit is localized in the nucleus during G1 and in the cytoplasm during S. Taken together, our results suggest that CKII may play significant roles in cell division control by shifting its localization between the cytoplasm and nucleus.
117 citations
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TL;DR: The results show a distinct redistribution of AKAP95 during mitosis, suggesting that the interaction between AKAP 95 and RIIalpha may be cell cycle-dependent.
117 citations
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TL;DR: An Arabidopsis mutant, named tardy asynchronous meiosis (tam), that exhibits a phenotype of delayed and asynchronous cell divisions during male meiosis is described, suggesting that the TAM protein positively regulates cell cycle progression, perhaps by promoting the G2/M transition.
Abstract: Male meiosis in higher organisms features synchronous cell divisions in a large number of cells. It is not clear how this synchrony is achieved, nor is it known whether the synchrony is linked to the regulation of cell cycle progression. Here, we describe an Arabidopsis mutant, named tardy asynchronous meiosis ( tam ), that exhibits a phenotype of delayed and asynchronous cell divisions during male meiosis. In Arabidopsis, two nuclear divisions occur before simultaneous cytokinesis yields a tetrad of haploid cells. In tam , cell divisions are delayed, resulting in the formation of abnormal intermediates, most frequently dyad meiotic products, or in rare cases, dyad pollen (two gametophytes within one exine wall). Temperature-shift experiments showed that the percentage of the abnormal intermediates increased at 27°C. Analysis of tam and the tam / quartet1 double mutant showed that most of these abnormal intermediates could continue through the normal rounds of cell divisions and form functional pollen, though at a slower than normal pace. The asynchrony of cell division started at the G2/M transition, with cells entering metaphase at different time points, during both meiosis I and II. In addition, chromosome condensation defects and mis-segregation were sometimes observed in tam . These observations suggest that the TAM protein positively regulates cell cycle progression, perhaps by promoting the G2/M transition. We speculate that there is a signal, perhaps TAM, that couples the normal pace of cell cycle progression with the synchrony of cell division during male meiosis.
117 citations