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PLoS Genetics 2012the synaptonemal complex (SC) links two meiotic prophase chromosomal events: homolog pairing and crossover recombination. SC formation involves the multimeric assembly...
the synaptonemal complex (SC) links two meiotic prophase chromosomal events: homolog pairing and crossover recombination. SC formation involves the multimeric assembly of coiled-coil proteins (Zip1 in budding yeast) at the interface of aligned homologous chromosomes. However, SC assembly is indifferent to homology and thus is normally regulated such that it occurs only subsequent to homology recognition. Assembled SC structurally interfaces with and influences the level and distribution of interhomolog crossover recombination events. Despite its involvement in dynamic chromosome behaviors such as homolog pairing and recombination, the extent to which SC, once installed, acts as an irreversible tether or maintains the capacity to remodel is not clear. Experiments presented here reveal insight into the dynamics of the full-length SC in budding yeast meiotic cells. We demonstrate that Zip1 continually incorporates into previously assembled synaptonemal complex during meiotic prophase. Moreover, post-synapsis Zip1 incorporation is sufficient to rescue the sporulation defect triggered by SCs built with a mutant version of Zip1, Zip1-4LA. Post-synapsis Zip1 incorporation occurs initially with a non-uniform spatial distribution, predominantly associated with Zip3, a component of the synapsis initiation complex that is presumed to mark a subset of crossover sites. A non-uniform dynamic architecture of the SC is observed independently of (i) synapsis initiation components, (ii) the Pch2 and Pph3 proteins that have been linked to Zip1 regulation, and (iii) the presence of a homolog. Finally, the rate of SC assembly and SC central region size increase in proportion to Zip1 copy number; this and other observations suggest that Zip1 does not exit the SC structure to the same extent that it enters. Our observations suggest that, after full-length assembly, SC central region exhibits little global turnover but maintains differential assembly dynamics at sites whose distribution is patterned by a recombination landscape.
Topics: Biological Transport; Cell Cycle Checkpoints; Centromere; Chromosome Pairing; Chromosomes; Nuclear Proteins; Phosphoprotein Phosphatases; Prophase; Protein Binding; Protein Subunits; Saccharomycetales; Synaptonemal Complex
PubMed: 23071451
DOI: 10.1371/journal.pgen.1002993 -
Developmental Cell Mar 2004Pairing of homologous chromosomes is important for homologous recombination and correct chromosome segregation during meiosis. It has been proposed that telomere... (Comparative Study)
Comparative Study
Pairing of homologous chromosomes is important for homologous recombination and correct chromosome segregation during meiosis. It has been proposed that telomere clustering, nuclear oscillation, and recombination during meiotic prophase facilitate homologous chromosome pairing in fission yeast. Here we examined the contributions of these chromosomal events to homologous chromosome pairing, by directly observing the dynamics of chromosomal loci in living cells of fission yeast. Homologous loci exhibited a dynamic process of association and dissociation during the time course of meiotic prophase. Lack of nuclear oscillation reduced association frequency for both centromeric and arm regions of the chromosome. Lack of telomere clustering or recombination reduced association frequency at arm regions, but not significantly at centromeric regions. Our results indicate that homologous chromosomes are spatially aligned by oscillation of telomere-bundled chromosomes and physically linked by recombination at chromosome arm regions; this recombination is not required for association of homologous centromeres.
Topics: Cell Nucleus; Chromosome Pairing; Chromosomes, Fungal; Gene Expression Regulation, Fungal; Green Fluorescent Proteins; Histones; In Situ Hybridization, Fluorescence; Karyometry; Luminescent Proteins; Meiosis; Metaphase; Mutation; Prophase; Reverse Transcriptase Polymerase Chain Reaction; Schizosaccharomyces; Schizosaccharomyces pombe Proteins; Telomere; Time Factors
PubMed: 15030757
DOI: 10.1016/s1534-5807(04)00059-0 -
Developmental Cell Dec 2010Accurate segregation of chromosomes during cell division is accomplished through the assembly of a bipolar microtubule-based structure called the mitotic spindle. Work... (Review)
Review
Accurate segregation of chromosomes during cell division is accomplished through the assembly of a bipolar microtubule-based structure called the mitotic spindle. Work over the past two decades has identified a core regulator of spindle bipolarity, the microtubule motor protein kinesin-5. However, an increasing body of evidence has emerged demonstrating that kinesin-5-independent mechanisms driving bipolar spindle assembly exist as well. Here, we discuss different pathways that promote initial centrosome separation and bipolar spindle assembly.
Topics: Animals; Biomechanical Phenomena; Cell Division; Centrosome; Humans; Kinesins; Kinetochores; Microtubules; Models, Biological; Molecular Motor Proteins; Nuclear Envelope; Prophase; Spindle Apparatus
PubMed: 21145497
DOI: 10.1016/j.devcel.2010.11.011 -
The Journal of Cell Biology Oct 1999We have used microinjection and time-lapse video microscopy to study the role of cyclin A in mitosis. We have injected purified, active cyclin A/cyclin-dependent kinase...
We have used microinjection and time-lapse video microscopy to study the role of cyclin A in mitosis. We have injected purified, active cyclin A/cyclin-dependent kinase 2 (CDK2) into synchronized cells at specific points in the cell cycle and assayed its effect on cell division. We find that cyclin A/CDK2 will drive G2 phase cells into mitosis within 30 min of microinjection, up to 4 h before control cells enter mitosis. Often this premature mitosis is abnormal; the chromosomes do not completely condense and daughter cells fuse. Remarkably, microinjecting cyclin A/CDK2 into S phase cells has no effect on progress through the following G2 phase or mitosis. In complementary experiments we have microinjected the amino terminus of p21(Cip1/Waf1/Sdi1) (p21N) into cells to inhibit cyclin A/CDK2 activity. We find that p21N will prevent S phase or G2 phase cells from entering mitosis, and will cause early prophase cells to return to interphase. These results suggest that cyclin A/CDK2 is a rate-limiting component required for entry into mitosis, and for progress through mitosis until late prophase. They also suggest that cyclin A/CDK2 may be the target of the recently described prophase checkpoint.
Topics: CDC2-CDC28 Kinases; Cyclin A; Cyclin-Dependent Kinase 2; Cyclin-Dependent Kinases; HeLa Cells; Humans; Microinjections; Microscopy, Video; Mitosis; Prophase; Protein Serine-Threonine Kinases
PubMed: 10525536
DOI: 10.1083/jcb.147.2.295 -
The Journal of Cell Biology Oct 2005The arrest of meiotic prophase in mouse oocytes within antral follicles requires the G protein G(s) and an orphan member of the G protein-coupled receptor family, GPR3.... (Comparative Study)
Comparative Study
The arrest of meiotic prophase in mouse oocytes within antral follicles requires the G protein G(s) and an orphan member of the G protein-coupled receptor family, GPR3. To determine whether GPR3 activates G(s), the localization of Galpha(s) in follicle-enclosed oocytes from Gpr3(+/+) and Gpr3(-/-) mice was compared by using immunofluorescence and Galpha(s)GFP. GPR3 decreased the ratio of Galpha(s) in the oocyte plasma membrane versus the cytoplasm and also decreased the amount of Galpha(s) in the oocyte. Both of these properties indicate that GPR3 activates G(s). The follicle cells around the oocyte are also necessary to keep the oocyte in prophase, suggesting that they might activate GPR3. However, GPR3-dependent G(s) activity was similar in follicle-enclosed and follicle-free oocytes. Thus, the maintenance of prophase arrest depends on the constitutive activity of GPR3 in the oocyte, and the follicle cell signal acts by a means other than increasing GPR3 activity.
Topics: Animals; Cells, Cultured; Female; GTP-Binding Protein alpha Subunits, Gs; Green Fluorescent Proteins; Immunohistochemistry; Meiosis; Mice; Mice, Knockout; Oocytes; Ovarian Follicle; Prophase; Receptors, G-Protein-Coupled
PubMed: 16247026
DOI: 10.1083/jcb.200506194 -
Tanpakushitsu Kakusan Koso. Protein,... Jun 2004
Review
Topics: Adenosine Triphosphatases; Animals; Aurora Kinases; Cell Cycle Proteins; Cell Nucleus; Centromere; Chromatin; Chromosomal Proteins, Non-Histone; Chromosomes; Cyclin B1; Cyclin-Dependent Kinases; DNA-Binding Proteins; Drosophila Proteins; Fungal Proteins; Histones; Humans; Microtubules; Multiprotein Complexes; Nuclear Proteins; Phosphorylation; Prophase; Protein Serine-Threonine Kinases; Spindle Apparatus; Tubulin; Cohesins
PubMed: 15209214
DOI: No ID Found -
The Journal of Cell Biology Aug 1998When vertebrate somatic cells are selectively irradiated in the nucleus during late prophase (<30 min before nuclear envelope breakdown) they progress normally through...
Entry into mitosis in vertebrate somatic cells is guarded by a chromosome damage checkpoint that reverses the cell cycle when triggered during early but not late prophase.
When vertebrate somatic cells are selectively irradiated in the nucleus during late prophase (<30 min before nuclear envelope breakdown) they progress normally through mitosis even if they contain broken chromosomes. However, if early prophase nuclei are similarly irradiated, chromosome condensation is reversed and the cells return to interphase. Thus, the G2 checkpoint that prevents entry into mitosis in response to nuclear damage ceases to function in late prophase. If one nucleus in a cell containing two early prophase nuclei is selectively irradiated, both return to interphase, and prophase cells that have been induced to returned to interphase retain a normal cytoplasmic microtubule complex. Thus, damage to an early prophase nucleus is converted into a signal that not only reverses the nuclear events of prophase, but this signal also enters the cytoplasm where it inhibits e.g., centrosome maturation and the formation of asters. Immunofluorescent analyses reveal that the irradiation-induced reversion of prophase is correlated with the dephosphorylation of histone H1, histone H3, and the MPM2 epitopes. Together, these data reveal that a checkpoint control exists in early but not late prophase in vertebrate cells that, when triggered, reverses the cell cycle by apparently downregulating existing cyclin-dependent kinase (CDK1) activity.
Topics: Animals; Antibodies, Monoclonal; Cell Cycle; Cell Nucleus; Cells, Cultured; Chromosomes; Dipodomys; Epitopes; Fluorescent Antibody Technique; Histones; Interphase; Kidney; Lasers; Microscopy, Video; Mitosis; Nuclear Envelope; Phosphoproteins; Prophase; Rats
PubMed: 9722613
DOI: 10.1083/jcb.142.4.1013 -
Current Topics in Developmental Biology 1998
Review
Topics: Animals; Cell Division; Chromosomes; G2 Phase; Gametogenesis; Mammals; Meiosis; Prophase; Sex Characteristics
PubMed: 9352191
DOI: 10.1016/s0070-2153(08)60179-9 -
The Journal of Biophysical and... Jul 1956The prophase chromosomes of the first meiotic division in pigeon, cat, and man contain a central structure or core consisting of a pair of dense fibrils (450 A) that are...
The prophase chromosomes of the first meiotic division in pigeon, cat, and man contain a central structure or core consisting of a pair of dense fibrils (450 A) that are parallel to one another and equidistant from a delicate linear region of increased density midway between them. These parallel strands are present early in prophase and the chromosomes seem to arise by congregation and organization of the chromatin granules around them. They have not been observed in mitosis or in other stages of meiosis.
Topics: Animals; Cats; Chromosomes; Humans; Male; Meiosis; Mitosis; Prophase; Spermatocytes; Vertebrates
PubMed: 13357504
DOI: 10.1083/jcb.2.4.403 -
Cell Motility and the Cytoskeleton 1990
Review
Topics: Anaphase; Animals; Microtubules; Plankton; Prophase; Schizosaccharomyces; Spindle Apparatus
PubMed: 2198114
DOI: 10.1002/cm.970160203