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The FEBS Journal Jul 2015In meiosis, homologous chromosomes face the obstacle of finding, holding onto and segregating away from their partner chromosome. There is increasing evidence, in a... (Review)
Review
In meiosis, homologous chromosomes face the obstacle of finding, holding onto and segregating away from their partner chromosome. There is increasing evidence, in a diverse range of organisms, that centromere-centromere interactions that occur in late prophase are an important mechanism in ensuring segregation fidelity. Centromere pairing appears to initiate when homologous chromosomes synapse in meiotic prophase. Structural proteins of the synaptonemal complex have been shown to help mediate centromere pairing, but how the structure that maintains centromere pairing differs from the structure of the synaptonemal complex along the chromosomal arms remains unknown. When the synaptonemal complex proteins disassemble from the chromosome arms in late prophase, some of these synaptonemal complex components persist at the centromeres. In yeast and Drosophila these centromere-pairing behaviors promote the proper segregation of chromosome partners that have failed to become linked by chiasmata. Recent studies of mouse spermatocytes have described centromere pairing behaviors that are similar in several respects to what has been described in the fly and yeast systems. In humans, chromosomes that fail to experience crossovers in meiosis are error-prone and are a major source of aneuploidy. The finding that centromere pairing is a conserved phenomenon raises the possibility that it may play a role in promoting the segregation fidelity of non-exchange chromosome pairs in humans.
Topics: Animals; Centromere; Chromosome Pairing; Chromosome Segregation; Humans; Meiosis; Synaptonemal Complex
PubMed: 25817724
DOI: 10.1111/febs.13280 -
Cell Cycle (Georgetown, Tex.) Oct 2016
Topics: Cell Cycle Proteins; Chromosomal Proteins, Non-Histone; Chromosome Pairing; Chromosomes; Meiosis; Synaptonemal Complex
PubMed: 27359070
DOI: 10.1080/15384101.2016.1204853 -
EMBO Reports Apr 2002The nuclear accumulation of active M-phase promoting factor (MPF) during prophase is thought to be essential for coordinating M-phase events in vertebrate cells. The...
The nuclear accumulation of active M-phase promoting factor (MPF) during prophase is thought to be essential for coordinating M-phase events in vertebrate cells. The protein phosphatase Cdc25C, an activator of MPF, enters the nucleus to keep MPF active in the nucleus during prophase. However, the molecular mechanisms that control nuclear translocation of Cdc25C during prophase are unknown. We show that phosphorylation of a serine residue (Ser198) in a nuclear export signal sequence of human Cdc25C occurs during prophase and promotes nuclear localization of Cdc25C. We also show that Polo-like kinase 1 (Plk1) is responsible for this phosphorylation and that constitutively active Plk1 promotes nuclear localization of Cdc25C. Remarkably, a mutant Cdc25C in which Ser198 is replaced by alanine remains in the cytoplasm when wild-type Cdc25C accumulates in the nucleus during prophase. These results suggest that Plk1 phosphorylates Cdc25C on Ser198 and regulates nuclear translocation of Cdc25C during prophase.
Topics: Cell Cycle Proteins; Cell Nucleus; Cyclin B; Cyclin B1; HeLa Cells; Humans; Phosphorylation; Prophase; Protein Kinases; Protein Serine-Threonine Kinases; Protein Transport; Proto-Oncogene Proteins; Serine; cdc25 Phosphatases; Polo-Like Kinase 1
PubMed: 11897663
DOI: 10.1093/embo-reports/kvf069 -
Proceedings of the National Academy of... Aug 1996A physical connection between homologs is required for reductional segregation at the first division of meiosis. This connection is usually provided by one or a few... (Review)
Review
A physical connection between homologs is required for reductional segregation at the first division of meiosis. This connection is usually provided by one or a few well-spaced crossovers. A speculative overview of processes leading to formation of these crossovers is presented.
Topics: Animals; Biological Evolution; Cell Cycle; Chromosomes; Crossing Over, Genetic; Humans; Meiosis; Mitosis; Plants; Prophase; Recombination, Genetic; Saccharomyces cerevisiae; Synaptonemal Complex
PubMed: 8710842
DOI: 10.1073/pnas.93.16.8167 -
Nature Plants Dec 2023The synaptonemal complex (SC) is a proteinaceous structure that forms between homologous chromosomes during meiosis prophase. The SC is widely conserved across species,...
The synaptonemal complex (SC) is a proteinaceous structure that forms between homologous chromosomes during meiosis prophase. The SC is widely conserved across species, but its structure and roles during meiotic recombination are still debated. While the SC central region is made up of transverse filaments and central element proteins in mammals and fungi, few central element proteins have been identified in other species. Here we report the identification of two coiled-coil proteins, SCEP1 and SCEP2, that form a complex and localize at the centre of the Arabidopsis thaliana SC. In scep1 and scep2 mutants, chromosomes are aligned but not synapsed (the ZYP1 transverse filament protein is not loaded), crossovers are increased compared with the wild type, interference is lost and heterochiasmy is strongly reduced. We thus report the identification of two plant SC central elements, and homologues of these are found in all major angiosperm clades.
Topics: Animals; Synaptonemal Complex; Prophase; Arabidopsis; Arabidopsis Proteins; Meiosis; Mammals
PubMed: 37973938
DOI: 10.1038/s41477-023-01558-y -
Nature Structural & Molecular Biology May 2016The synaptonemal complex (SC) is a meiosis-specific scaffold that links homologous chromosomes from end to end during meiotic prophase and is required for the formation... (Review)
Review
The synaptonemal complex (SC) is a meiosis-specific scaffold that links homologous chromosomes from end to end during meiotic prophase and is required for the formation of meiotic crossovers. Assembly of SC components is regulated by a combination of associated nonstructural proteins and post-translational modifications, such as SUMOylation, which together coordinate the timing between homologous chromosome pairing, double-strand-break formation and recombination. In addition, transcriptional and translational control mechanisms ensure the timely disassembly of the SC after crossover resolution and before chromosome segregation at anaphase I.
Topics: Animals; Chromosome Pairing; Chromosome Segregation; Humans; Meiosis; Protein Processing, Post-Translational; Synaptonemal Complex
PubMed: 27142324
DOI: 10.1038/nsmb.3208 -
Zhongguo Shi Yan Xue Ye Xue Za Zhi Dec 2004Chfr, a mitotic stress checkpoint gene, regulates a prophase delay in cells exposed to agents that disrupt microtubules, such as nocodazole and taxol. Chfr expression... (Review)
Review
Chfr, a mitotic stress checkpoint gene, regulates a prophase delay in cells exposed to agents that disrupt microtubules, such as nocodazole and taxol. Chfr expression was ubiquitious in normal human tissues. It is very high conserved between human and mice. Preliminary sutdies indicated that Chfr expression was cell cycle regulated and it dependent on its ubiqitin ligase activity. The direct target of the Chfr pathway was Polo-like kinase 1 (Plk1). Ubiquitination of Plk1 by Chfr delayed the activation of the Cdc25C phosphatase and the inactivation of the Weel kinase, leading to a delay in Cdc 2 activation. The chfr gene was inactivated owing to lack of expression or by mutation in some human cancer cell lines examined. Normal primary cells and tumour cell lines that express wild-type chfr exhibited delayed entry into metaphase when centrosome separation was inhibited by mitotic stress. In contrast, the tumour cell lines that had lost chfr function entered metaphase without delay. Ecotopic expression of wild-type chfr restored the cell cycle delay and increased the ability of the cells to survive mitotic stress. Thus, chfr defines a checkpoint that delays entry into metaphase in response to mitotic stress. The progress of research on structure of Chfr gene and effects of Chfr protein was reviewed.
Topics: Cell Cycle; Cell Cycle Proteins; Humans; Metaphase; Mitosis; Neoplasm Proteins; Neoplasms; Poly-ADP-Ribose Binding Proteins; Prophase; Protein Serine-Threonine Kinases; Protein-Tyrosine Kinases; Proto-Oncogene Proteins; Ubiquitin-Protein Ligases; Polo-Like Kinase 1
PubMed: 15631682
DOI: No ID Found -
Molecular Biology of the Cell Oct 2007In higher eukaryotic cells, microtubules within metaphase and anaphase spindles undergo poleward flux, the slow, poleward movement of tubulin subunits through the...
In higher eukaryotic cells, microtubules within metaphase and anaphase spindles undergo poleward flux, the slow, poleward movement of tubulin subunits through the spindle microtubule lattice. Although a number of studies have documented this phenomenon across a wide range of model systems, the possibility of poleward flux before nuclear envelope breakdown (NEB) has not been examined. Using a mammalian cell line expressing photoactivatable green fluorescent protein (GFP)-tubulin, we observe microtubule motion, both toward and away from centrosomes, at a wide range of rates (0.5-4.5 microm/min) in prophase cells. Rapid microtubule motion in both directions is dynein dependent. In contrast, slow microtubule motion, which occurs at rates consistent with metaphase flux, is insensitive to inhibition of dynein but sensitive to perturbation of Eg5 and Kif2a, two proteins with previously documented roles in flux. Our results demonstrate that microtubules in prophase cells are unexpectedly dynamic and that a subpopulation of these microtubules shows motion that is consistent with flux. We propose that the marked reduction in rate and directionality of microtubule motion from prophase to metaphase results from changes in microtubule organization during spindle formation.
Topics: Animals; Dyneins; Kinesins; Microtubules; Movement; Nuclear Envelope; Prometaphase; Prophase; Pyrimidines; Swine; Thiones
PubMed: 17671163
DOI: 10.1091/mbc.e07-05-0420 -
Human Genetics May 1990Observations at the electron microscope (EM) level have been made on 1883 primary spermatocytes from 40 chromosomally normal subfertile men and 566 spermatocytes from 10... (Comparative Study)
Comparative Study
Observations at the electron microscope (EM) level have been made on 1883 primary spermatocytes from 40 chromosomally normal subfertile men and 566 spermatocytes from 10 fertile controls, using the technique of microspreading. Spermatocytes of infertile men in general showed greater indications of degeneration including higher levels of background silver deposition, nucleolar organising region - XY associations, fragmentation of synaptonemal complexes and overproduction of XY excrescences. A few oligospermic men also showed an immature morphology of the XY pair and/or a reduced extent of XY synapsis. Dissociation of the sex chromosome axes at prophase was found to occur with a much lower frequency than that recorded for separated X and Y chromosomes at metaphase I. In a single spermatocyte, synaptonemal complex formation was observed between Xqter and Yqter, a situation that could enable rare XqYq interchange. A proteinaceous stalked body exists on the Y axis towards its non-pairing end; this structure might have a functional relationship with the gene for spermatogenesis, (AZF), located at the euchromatin/heterochromatin interface. Compared with human oocytes, spermatocytes show fewer anomalies of synapsis, i.e. asynapsed segments or whole axes, non-homologous associations, interchanges, interlocks. These latter data agree well with findings from the mouse.
Topics: Adult; Aged; Aged, 80 and over; Chromosomes, Human; Female; Humans; Infertility, Male; Male; Meiosis; Microscopy, Electron; Middle Aged; Oocytes; Prophase; Sex Chromosomes; Spermatocytes; Synaptonemal Complex
PubMed: 2338341
DOI: 10.1007/BF00210808 -
Cell Biology International Reports Aug 1992
Review
Topics: Animals; Drosophila; Male; Prophase; Rats; Spermatocytes; Synaptonemal Complex
PubMed: 1446349
DOI: 10.1016/s0309-1651(05)80019-0