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.

CENP-meta, an Essential Kinetochore Kinesin Required for the Maintenance of Metaphase Chromosome Alignment in Drosophila

Abstract: CENP-meta has been identified as an essential, kinesin-like motor protein in Drosophila. The 257-kD CENP-meta protein is most similar to the vertebrate kinetochore-associated kinesin-like protein CENP-E, and like CENP-E, is shown to be a component of centromeric/kinetochore regions of Drosophila chromosomes. However, unlike CENP-E, which leaves the centromere/kinetochore region at the end of anaphase A, the CENP-meta protein remains associated with the centromeric/kinetochore region of the chromosome during all stages of the Drosophila cell cycle. P-element–mediated disruption of the CENP-meta gene leads to late larval/pupal stage lethality with incomplete chromosome alignment at metaphase. Complete removal of CENP-meta from the female germline leads to lethality in early embryos resulting from defects in metaphase chromosome alignment. Real-time imaging of these mutants with GFP-labeled chromosomes demonstrates that CENP-meta is required for the maintenance of chromosomes at the metaphase plate, demonstrating that the functions required to establish and maintain chromosome congression have distinguishable requirements.

Shugoshin protects cohesin complexes at centromeres

Abstract: The different regulation of sister chromatid cohesion at centromeres and along chromosome arms is obvious during meiosis, because centromeric cohesion, but not arm cohesion, persists throughout anaphase of the first division. A protein required to protect centromeric cohesin Rec8 from separase cleavage has been identified and named shugoshin (or Sgo1) after shugoshin (‘guardian spirit’ in Japanese). It has become apparent that shugoshin shows marginal homology with Drosophila Mei-S332 and several uncharacterized proteins in other eukaryotic organisms. Because Mei-S332 is a protein previously shown to be required for centromeric cohesion in meiosis, it is now established that shugoshin represents a conserved protein family defined as a centromeric protector of Rec8 cohesin complexes in meiosis. The regional difference of sister chromatid cohesion is also observed during mitosis in vertebrates; the cohesion is much more robust at the centromere at metaphase, where it antagonizes the pulling force of spindle microtubules that attach the kinetochores from opposite poles. The human shugoshin homologue (hSgo1) is required to protect the centromeric localization of the mitotic cohesin, Scc1, until metaphase. Bub1 plays a crucial role in the localization of shugoshin to centromeres in both fission yeast and humans.

Zytologische studien an allium schoenoprasum

Abstract: In this study, chromosome painting technique was performed to analyse the abnormal karyotypes of two carriers. Chromosome 18 and 7 specific libraries, which were generated by chromosome microdissection technique, were used as probe pools to hybridize the carriers^ metaphase chromosomes respectively. Unlabled human genomic DNA was used to inhibit the hybridization of sequences in the library that bind to mutiple chromosomes. Structure abnormality was detected clearly in metaphase. Combined with the banding chromosomes, we concluded that their karytypes were 46, XY, t (3; 18) (q21; q21) and 46, XX, dir ins (1; 7) (p3104; q34q36). Chromosome painting, as a direct and concise method in analysing chromosome structure abnormality, is an important complement and development of chromosome banding technique, and has important application in genetic counselling and prenatal diagnosis.

Metaphase Chromosome Tethering Is Necessary for the DNA Synthesis and Maintenance of oriP Plasmids but Is Insufficient for Transcription Activation by Epstein-Barr Nuclear Antigen 1

Abstract: Epstein-Barr Virus (EBV) infects resting B cells, within which it establishes latency as a stable, circular episome with only two EBV components, the cis element oriP and the latently expressed protein EBNA1. It is believed that EBNA1's ability to tether oriP episomes to metaphase chromosomes is required for its stable replication. We created fusions between the DNA-binding domain (DBD) of EBNA1 and the cellular chromatin-binding proteins HMGA1a and HMG1 to determine the minimal requirements for stable maintenance of an oriP-based episome. These two proteins differ in that HMGA1a can associate with metaphase chromosomes but HMG1 cannot. Interestingly, coinciding with metaphase chromosome association, HMGA1a-DBD but not HMG1-DBD supported both the transient replication and stable maintenance of oriP plasmids, with efficiencies quantitatively similar to that of EBNA1. However, HMGA1a-DBD activated transcription from EBNA1-dependent episomal reporter to only 20% of the level of EBNA1. Furthermore, EBNA1 but not HMGA1a-DBD activated transcription from a chromosomally integrated EBNA1-dependent transcription reporter. This indicates that EBNA1 possesses functional domains that support transcription activation independent of its ability to tether episomal oriP plasmids to cellular chromosomes. We provide evidence that metaphase chromosome tethering is a fundamental requirement for maintenance of an oriP plasmid but is insufficient for EBNA1 to activate transcription.

Polyribosome disaggregation during metaphase.

Abstract: Polyribosomes as examined by both sucrose-gradient analysis and electron microscopy disaggregate during metaphase in both normal HeLa cells and those arrested in metaphase by treatment with colchicine.