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.
Papers published on a yearly basis
Papers
More filters
••
TL;DR: The authors' data support catalytic models of checkpoint activation where Mad1 and Bub1 are mainly resident, Mad2 free of Mad1, BubR1 andbub3 free of Bub1, CDC20, and Mps1 dynamically exchange as part of the diffuse wait-anaphase signal; and Mad2 interacts with Cdc20 at unattached kinetochores.
375 citations
••
TL;DR: Nocodazole has very little effect on interphase metabolism, and following drug release, cells return to a normal cell cycle.
374 citations
••
TL;DR: Results imply that centromeric cohesion, one of the hallmarks of mitotic chromosomes, is not an intrinsically stable property, because it can easily be destroyed by mitotic kinases, which are kept in check by shugoshin.
Abstract: Cohesion between sister chromatids is essential for their bi-orientation on mitotic spindles. It is mediated by a multisubunit complex called cohesin. In yeast, proteolytic cleavage of cohesin's α kleisin subunit at the onset of anaphase removes cohesin from both centromeres and chromosome arms and thus triggers sister chromatid separation. In animal cells, most cohesin is removed from chromosome arms during prophase via a separase-independent pathway involving phosphorylation of its Scc3-SA1/2 subunits. Cohesin at centromeres is refractory to this process and persists until metaphase, whereupon its α kleisin subunit is cleaved by separase, which is thought to trigger anaphase. What protects centromeric cohesin from the prophase pathway? Potential candidates are proteins, known as shugoshins, that are homologous to Drosophila MEI-S332 and yeast Sgo1 proteins, which prevent removal of meiotic cohesin complexes from centromeres at the first meiotic division. A vertebrate shugoshin-like protein associates with centromeres during prophase and disappears at the onset of anaphase. Its depletion by RNA interference causes HeLa cells to arrest in mitosis. Most chromosomes bi-orient on a metaphase plate, but precocious loss of centromeric cohesin from chromosomes is accompanied by loss of all sister chromatid cohesion, the departure of individual chromatids from the metaphase plate, and a permanent cell cycle arrest, presumably due to activation of the spindle checkpoint. Remarkably, expression of a version of Scc3-SA2 whose mitotic phosphorylation sites have been mutated to alanine alleviates the precocious loss of sister chromatid cohesion and the mitotic arrest of cells lacking shugoshin. These data suggest that shugoshin prevents phosphorylation of cohesin's Scc3-SA2 subunit at centromeres during mitosis. This ensures that cohesin persists at centromeres until activation of separase causes cleavage of its α kleisin subunit. Centromeric cohesion is one of the hallmarks of mitotic chromosomes. Our results imply that it is not an intrinsically stable property, because it can easily be destroyed by mitotic kinases, which are kept in check by shugoshin.
374 citations
••
TL;DR: The data reveal that the primary role of the centrosome in somatic cells is not to form the spindle but instead to ensure cytokinesis and subsequent cell cycle progression.
Abstract: When centrosomes are destroyed during prophase by laser microsurgery, vertebrate somatic cells form bipolar acentrosomal mitotic spindles (Khodjakov, A., R.W. Cole, B.R. Oakley, and C.L. Rieder. 2000. Curr. Biol. 10:59-67), but the fate of these cells is unknown. Here, we show that, although these cells lack the radial arrays of astral microtubules normally associated with each spindle pole, they undergo a normal anaphase and usually produce two acentrosomal daughter cells. Relative to controls, however, these cells exhibit a significantly higher (30-50%) failure rate in cytokinesis. This failure correlates with the inability of the spindle to properly reposition itself as the cell changes shape. Also, we destroyed just one centrosome during metaphase and followed the fate of the resultant acentrosomal and centrosomal daughter cells. Within 72 h, 100% of the centrosome-containing cells had either entered DNA synthesis or divided. By contrast, during this period, none of the acentrosomal cells had entered S phase. These data reveal that the primary role of the centrosome in somatic cells is not to form the spindle but instead to ensure cytokinesis and subsequent cell cycle progression.
367 citations
••
TL;DR: It is reported that H3 phosphorylation occurs at Ser28, as well as at Ser10 during mitosis, at least in mammals, and Aurora B was recently demonstrated to be responsible for Ser10 phosphorylated in S. cerevisiae, Drosophila and Xenopus egg extract.
Abstract: BACKGROUND: Histone H3 (H3) phosphorylation plays important roles in mitotic chromosome condensation We reported that H3 phosphorylation occurs at Ser28, as well as at Ser10 during mitosis, at least in mammals Aurora B was recently demonstrated to be responsible for Ser10 phosphorylation in S cerevisiae, C elegans, Drosophila and Xenopus egg extract RESULTS: We compared the distribution of Aurora-B with that of H3 phosphorylation Aurora-B was primarily localized in the heterochromatin of late G2 phase cells, where only Ser10 phosphorylation was observed The treatment of such cells with calyculin A induced Ser28 phosphorylation in the Aurora-B-localized area During prophase to metaphase, Aurora-B was distributed in condensing chromosomes where Ser10 and Ser28 were phosphorylated Aurora-B can phosphorylate H3-Ser10 and -Ser28 in nucleosomes in vitro Transfection of a dominant-negative mutant of Aurora-B resulted in a reduction of H3 phosphorylation, not only at Ser10 but also Ser28, during mitosis CONCLUSIONS: With regard to mitotic chromosome condensation, Aurora-B directly phosphorylated H3, not only at Ser10 but also at Ser28 The level of Ser28 phosphorylation is diminished to undetectable levels by PP1 phosphatase prior to entry into mitosis
365 citations