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Oócitos aparentemente maduros injetados em telófase I apresentam piores resultados de reprodução assistida; Apparently matured oocytes injected in telophase I have worse outcomes from assisted reproduction

Dib, Luciana Azôr; Araújo, Maria Cristina Picinato Medeiros de; Giorgenon, Roberta Cristina; Ferriani, Rui Alberto; Navarro, Paula Andrea de Albuquerque Sales
Fonte: Federação Brasileira das Sociedades de Ginecologia e Obstetrícia Publicador: Federação Brasileira das Sociedades de Ginecologia e Obstetrícia
Tipo: Artigo de Revista Científica
POR
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OBJETIVO: Avaliar o estágio de maturação nuclear de oócitos com o primeiro corpúsculo polar (CP) visível de pacientes inférteis submetidas à estimulação ovariana para injeção intracitoplasmática de espermatozoide (ICSI) e comparar os resultados da injeção intracitoplasmática de espermatozoide entre os oócitos em telófase I (TI) e metáfase II (MII), e entre aqueles em metáfase II com e sem fuso celular visível. MÉTODOS: Estudo prospectivo que incluiu 106 pacientes inférteis submetidas à injeção intracitoplasmática de espermatozoide. Foram incluídas pacientes com idade menor ou igual a 38 anos, hormônio folículo estimulante (FSH) basal menor que 10 mIU/mL e índice de massa corpórea (IMC) menor que 30 kg/m². Foram excluídas pacientes com doenças sistêmicas, com qualquer infecção ativa, tabagistas ou que fizeram uso de medicações hormonais e anti-inflamatórias hormonais e não hormonais nos últimos dois meses, previamente à programação para o procedimento de reprodução assistida. Os oócitos com extrusão do primeiro corpúsculo polar foram avaliados pela microscopia de polarização, imediatamente antes da realização da injeção intracitoplasmática de espermatozoide, e caracterizados quanto ao estágio de maturação nuclear (telófase I ou metáfase II). Os oócitos em metáfase II foram avaliados de acordo com a presença ou não do fuso meiótico. Foram analisadas as taxas de fertilização...

Análise não invasiva do fuso celular de oócitos e os resultados dos procedimentos de reprodução assistida em mulheres inférteis com endometriose; Living human oocytes with first polar body extrusion from patients with moderate and severe endometriosis contain a higher percentage of telophase I oocytes.

Dib, Luciana Azôr
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 01/03/2010 PT
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Introdução: Apesar de controverso, questiona-se um papel deletério da endometriose nos resultados de procedimentos de reprodução assistida, o que pode estar relacionado ao comprometimento da qualidade oocitária. Para que o oócito maduro esteja preparado para a fertilização, é necessário que o fuso meiótico mantenha a sua integridade e funcionabilidade. Objetivos: Comparar a presença e localização do fuso meiótico e o estágio de maturação nuclear de oócitos com o primeiro corpúsculo polar (CP) visível de pacientes inférteis sem e com endometriose. Comparar os resultados de Injeção Intracitoplasmática de espermatozóides (ICSI) entre os oócitos em telófase I e metáfase II, e entre aqueles com e sem fuso celular visível, nos grupos analisados. Metodologia: Estudo prospectivo e controlado com pacientes inférteis, submetidas à estimulação ovariana para realização de ICSI, selecionadas consecutivamente e divididas em dois grupos: Controle (fator tubário e/ou masculino) e Endometriose (subdividido em endometriose mínima e leve I/II versus moderada e severa III/IV). Os oócitos com extrusão do primeiro CP foram avaliados pela microscopia de polarização imediatamente antes da realização da ICSI e caracterizados quanto à presença/localização do fuso celular em relação ao primeiro CP e ao estágio de maturação nuclear (telófase I ou metáfase II). Foram analisados as taxas de fertilização...

Contribution to the validation of the anaphase-telophase test: aneugenic and clastogenic effects of cadmium sulfate, potassium dichromate and nickel chloride in Chinese hamster ovary cells

Seoane,A.I.; Dulout,F.N.
Fonte: Sociedade Brasileira de Genética Publicador: Sociedade Brasileira de Genética
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/1999 EN
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There is increasing evidence that aneuploidy during mitosis may be a factor in the etiology of somatic malignancy. The analysis of alterations in anaphase-telophase of mitosis is a useful test for evaluating the aneuploidogenic and clastogenic ability of chemicals. Several metals have been found to be carcinogenic to humans and animals. However, the underlying mechanisms remain unclear. In the present study the aneugenic and clastogenic abilities of cadmium sulfate, potassium dichromate and nickel chloride were analyzed using the anaphase-telophase test. Chinese hamster ovary (CHO) cells cultured for two cycles were treated with the desired compound for 8 h before cell harvesting. The frequency of cells with chromatin bridges, lagging chromosomes and lagging chromosomal fragments was scored. The mitotic index was determined by counting the number of mitotic cells per 1,000 cells on each coverslip and was expressed as a percentage of the number of mitotic plates. Statistical comparisons were done using the "G" method. Correlation and regression analyses were performed to evaluate variations of the mitotic index. Chromium and cadmium were clastogenic and aneugenic and increased the frequencies of the three types of aberrations scored; nickel had only aneugenic activity because it increased the frequency of lagging chromosomes. These results indicate that the anaphase-telophase test is sufficiently sensitive to detect dose-response relationships that can distinguish clastogenic and/or aneugenic activities and that the results obtained using the anaphase-telophase test were similar to those obtained by chromosome counting.

Asymmetric Division in Fucoid Zygotes Is Positioned by Telophase Nuclei

Bisgrove, Sherryl R.; Henderson, David C.; Kropf, Darryl L.
Fonte: American Society of Plant Biologists Publicador: American Society of Plant Biologists
Tipo: Artigo de Revista Científica
Publicado em /04/2003 EN
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The relative contributions of cell polarity and nuclear position in specifying the plane of asymmetric division in fucoid zygotes were investigated. In zygotes developing normally, telophase nuclei were positioned parallel to the polar growth axis, and the division plane bisected both axes. To assess division plane specification, the colinearity of the nuclear and growth axes was uncoupled by treatment with pharmacological agents. Spatial correlations between the growth axis, telophase nuclei, and the division plane were analyzed in the treated zygotes. In all cases, cytokinesis was oriented transverse to the telophase mitotic array and was less well aligned with the growth axis. Telophase nuclei also played a predominant role in positioning the division plane in polyspermic zygotes. Microtubules from the telophase nuclei interdigitated throughout the plane of subsequent cytokinesis, and we speculate that they specify the division plane. Morphological markers of the division plane were not observed before telophase; the earliest division marker detected was a plate of actin that assembled in the zone of microtubule overlap late in telophase. These findings are consistent with division plane specification at cytoplast boundaries.

The Swi5 Transcription Factor of Saccharomyces Cerevisiae Has a Role in Exit from Mitosis through Induction of the Cdk-Inhibitor Sic1 in Telophase

Toyn, J. H.; Johnson, A. L.; Donovan, J. D.; Toone, W. M.; Johnston, L. H.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/1997 EN
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Deactivation of the B cyclin kinase (Cdc28/Clb) drives the telophase to G1 cell cycle transition. Here we investigate one of the control pathways that contributes to kinase deactivation, involving the cell cycle-regulated production of the cdk inhibitor Sic1. We show that the cell cycle timing of SIC1 expression depends on the transcription factor Swi5, and that Swi5-dependent SIC1 expression begins during telophase. In contrast to Swi5, the related transcription factor Ace2, which can also induce SIC1 expression, is not active during telophase. The functional consequence of Swi5-regulated SIC1 expression in vivo is that both sic1Δ and swi5Δ strains have identical mitotic exit-related phenotypes. First, both are synthetically lethal with dbf2Δ, resulting in cell cycle arrest in telophase. Second, both are hypersensitive to overexpression of the B cyclin CLB2. Thus, Swi5-dependent activation of the SIC1 gene contributes to the deactivation of the B cyclin kinase, and hence exit from mitosis.

Mammalian nuclei become licensed for DNA replication during late telophase

Dimitrova, Daniela S.; Prokhorova, Tatyana A.; Blow, J. Julian; Todorov, Ivan T.; Gilbert, David M.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/01/2002 EN
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Mcm 2–7 are essential replication proteins that bind to chromatin in mammalian nuclei during late telophase. Here, we have investigated the relationship between Mcm binding, licensing of chromatin for replication, and specification of the dihydrofolate reductase (DHFR) replication origin. Approximately 20% of total Mcm3 protein was bound to chromatin in Chinese hamster ovary (CHO) cells during telophase, while an additional 25% bound gradually and cumulatively throughout G1-phase. To investigate the functional significance of this binding, nuclei prepared from CHO cells synchronized at various times after metaphase were introduced into Xenopus egg extracts, which were either immunodepleted of Mcm proteins or supplemented with geminin, an inhibitor of the Mcm-loading protein Cdt1. Within 1 hour after metaphase, coincident with completion of nuclear envelope formation, CHO nuclei were fully competent to replicate in both of these licensing-defective extracts. However, sites of initiation of replication in each of these extracts were found to be dispersed throughout the DHFR locus within nuclei isolated between 1 to 5 hours after metaphase, but became focused to the DHFR origin within nuclei isolated after 5 hours post-metaphase. Importantly...

Some flow cytofluorimetric studies of the nuclear ploidy of mouse hepatocytes. II. Early changes in nuclear ploidy of mouse hepatocytes following carbon tetrachloride administration: evidence for polyploid nuclei arrested in telophase.

Steele, P. R.; Yim, A. P.; Herbertson, B. M.; Watson, J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1981 EN
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Mature mice have a large proportion of their hepatocyte nuclei in polyploid states (tetraploid and octaploid), and this is more prominent in females. We measured nuclear ploidy distribution cytometrically using ethidium bromide-stained hepatocyte nuclei liberated by in situ collagenase perfusion of the liver via the portal vein. After s.c. administration of 0.2 ml carbon tetrachloride the ploidy distributions of 8-month-old female mice changed from a control of 35% 2N, 45% 4N, and 20% 8N to 54% 2N, 45% 4N and 1% 8N at 6 h, and 65% 2N, 35% 4N and 0% 8N at 24 h. By 72 h 92% of the nuclei were diploid. These changes preceded any changes in mitotic index and S-phase index (3H-TdR autoradiographs). Histology confirmed the loss of higher-ploid nuclei but without mitotic figures or selective cell necrosis to account for the observations. Cleaved nuclei were prominent in sections of liver examined 3 h after CCl4 administration and suggested division of polypoid nuclei that had undergone prior segregation of chromatids and had presumably been arrested in telophase.

ELECTRON MICROSCOPIC STUDIES OF MITOSIS IN AMEBAE : II. The Giant Ameba Pelomyxa carolinensis

Roth, L. E.; Daniels, E. W.
Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 01/01/1962 EN
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Dividing nuclei from the giant ameba Pelomyxa carolinensis were fixed in osmium tetroxide solutions buffered with veronal acetate to pH 8.0. If divalent cations (0.002 M calcium, magnesium, or strontium as chlorides) were added to the fixation solution, fibrils that are 14 mµ in diameter and have a dense cortex are observed in the spindle. If the divalent ions were omitted, oriented particles of smaller size are present and fibrils are not obvious. The stages of mitosis were observed and spindle components compared. Fibrils fixed in the presence of calcium ions are not so well defined in early metaphase as later, but otherwise have the same diameter in the late metaphase, anaphase, and early telophase. Fibrils are surrounded by clouds of fine material except in early telophase, when they are formed into tight bundles lying in the cytoplasm unattached to nuclei. Metaphase and anaphase fibrils fixed without calcium ions are less well defined and are not observably different from each other. The observations are consistent with the concept that spindle fibrils are composed of polymerized, oriented protein molecules that are in equilibrium with and bathed in non-oriented molecules of the same protein. Partially formed spindle fibrils and ribosome-like particles were observed in the mixoplasm when the nuclear envelope had only small discontinuities. Remnants of the envelope are visible throughout division and are probably incorporated into the new envelope in the telophase. Ribosome-like particles are numerous in the metaphase and anaphase spindle but are not seen in the telophase nucleus...

TELOPHASE SEGREGATION OF CHROMOSOMES AND AMITOSIS

Molè-Bajer, J.
Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 01/04/1965 EN
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Cases of "distributive c-mitosis" (the term does not mean that colchicine has been used) in plant endosperm are described, in which the chromosomes of metaphase type (two-chromatid chromosomes) are distributed at random because of phragmoplast activity in a process similar to non-disjunction. There is some evidence that chromosmal fibres can be formed within the phragmoplast under special circumstances; during "distributive c-mitosis" some kinetochores show active movements due to cooperation with chromosomal fibres formed in the phragmoplast; while other chromosomes, as indicated by their arrangements and shape, are moved without any activity of kinetochores. Some components of the phragmoplast have the fastest movements occurring in mitosis. Some cases are described in which the phragmoplast divides telophase and interphase nuclei into two or more groups and moves the pieces a considerable distance apart. In a similar way, the phragmoplast may divide newly formed restitution nuclei. This phenomenon leads to a reduction of chromosome numbers, and the course of the process itself is reminiscent of amitosis.

Accumulation of adrenocorticotropin secretory granules in the midbody of telophase AtT20 cells: evidence that secretory granules move anterogradely along microtubules

Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 01/04/1987 EN
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During the cell cycle the distribution of the ACTH-containing secretory granules in AtT20 cells, as revealed by immunofluorescence labeling and electron microscopy of thin sections, undergoes a cycle of changes. In interphase cells the granules are concentrated in the Golgi region, where they form, and also at the tips of projections from the cells, where they accumulate. These projections contain many microtubules extending to their tips. During metaphase and anaphase the granules are randomly distributed in the cytoplasm of the rounded-up mitotic cells. On entry into telophase there is a rapid and striking redistribution of the granules, which accumulate in large numbers in the midbody as it develops during cytokinesis. This accumulation of secretory granules in the midbody is dependent upon the presence of microtubules. The changing pattern of distribution of the secretory granules during the cell cycle fulfills the predictions of a model envisaging first that secretory granules associate with and move along interphase microtubules in a net anterograde direction away from the centrioles, and secondly that they do not associate with microtubules of the mitotic spindle during metaphase and anaphase.

Interzone microtubule behavior in late anaphase and telophase spindles

Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 01/08/1987 EN
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We have studied microtubule behavior in late anaphase and telophase spindles of PtK1 cells, using fluoresceinated tubulin (DTAF-tubulin), microinjection, and laser microbeam photobleaching. We present the results of two novel tests which add to the evidence that DTAF-tubulin closely mimics the behavior of native tubulin in vivo. (a) Microinjected DTAF-tubulin was as effective as injected native tubulin in promoting division of taxol-dependent mitotic mutant cells that had been deprived of taxol. (b) Microinjected colchicine-DTAF-tubulin complex was similar to injected colchicine-native tubulin complex in causing depolymerization of spindles. Immediately after microinjection of DTAF-tubulin into wild-type cells during late anaphase or telophase, fluorescence incorporation by microtubules was seen in chromosomal half- spindles and just behind the chromosomes, but there was no fluorescence incorporation near the middle of the interzone. Over the next few minutes, tubulin fluorescence accumulated at the center of the interzone (the equator), becoming progressively more intense. In other experiments, cells were microinjected with DTAF-tubulin at prophase and allowed to equilibrate for 30 min. Cells that had progressed to late anaphase were then photobleached to reduce the fluorescence in the central portion of the interzone. Over a period of several minutes...

Differential interaction of splicing snRNPs with coiled bodies and interchromatin granules during mitosis and assembly of daughter cell nuclei

Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 01/07/1994 EN
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In the interphase nucleus of mammalian cells the U1, U2, U4/U6, and U5 small nuclear ribonucleoproteins (snRNPs), which are subunits of spliceosomes, associate with specific subnuclear domains including interchromatin granules and coiled bodies. Here, we analyze the association of splicing snRNPs with these structures during mitosis and reassembly of daughter nuclei. At the onset of mitosis snRNPs are predominantly diffuse in the cytoplasm, although a subset remain associated with remnants of coiled bodies and clusters of mitotic interchromatin granules, respectively. The number and size of mitotic coiled bodies remain approximately unchanged from metaphase to early telophase while snRNP-containing clusters of mitotic interchromatin granules increase in size and number as cells progress from anaphase to telophase. During telophase snRNPs are transported into daughter nuclei while the clusters of mitotic interchromatin granules remain in the cytoplasm. The timing of nuclear import of splicing snRNPs closely correlates with the onset of transcriptional activity in daughter nuclei. When transcription restarts in telophase cells snRNPs have a diffuse nucleoplasmic distribution. As cells progress to G1 snRNP- containing clusters of interchromatin granules reappear in the nucleus. Coiled bodies appear later in G1...

Delay of HeLa cell cleavage into interphase using dihydrocytochalasin B: retention of a postmitotic spindle and telophase disc correlates with synchronous cleavage recovery

Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 01/10/1995 EN
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The molecular signals that determine the position and timing of the cleavage furrow during mammalian cell cytokinesis are presently unknown. We have studied in detail the effect of dihydrocytochalasin B (DCB), a drug that interferes with actin assembly, on specific late mitotic events in synchronous HeLa cells. When cleavage furrow formation is blocked at 10 microM DCB, cells return to interphase by the criteria of reformation of nuclei with lamin borders, degradation of the cyclin B component of p34cdc2 kinase, and loss of mitosis specific MPM-2 antigens. However, the machinery for cell cleavage is retained for up to one hour into G1 when cleavage cannot proceed. The components retained consist prominently of a "postmitotic" spindle and a telophase disc, a structure templated by the mitotic spindle in anaphase that may determine the position and timing of the cleavage furrow. Upon release from DCB block, G1 cells proceed through a rapid and synchronous cleavage. We conclude that the mitotic spindle is not inevitably destroyed at the end of mitosis, but persists as an integral structure with the telophase disc in the absence of cleavage. We also conclude that cell cleavage can occur in G1, and is therefore an event metabolically independent of mitosis. The retained telophase disc may indeed signal the position of furrow formation...

Lte1, Cdc14 and MEN-controlled Cdk inactivation in yeast coordinate rDNA decompaction with late telophase progression

Varela, Elisa; Shimada, Kenji; Laroche, Thierry; Leroy, Didier; Gasser, Susan M
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
EN
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The mechanism of chromatin compaction in mitosis has been well studied, while little is known about what controls chromatin decompaction in early G1 phase. We have localized the Condensin subunit Brn1 to a compact spiral of rDNA in mitotic budding yeast cells. Brn1 release and the resulting rDNA decompaction in late telophase coincided with mitotic spindle dissociation, and occurred asymmetrically (daughter cells first). We immunoprecipitated the GTP-exchange factor Lte1, which helps activate the mitotic exit network (MEN) in anaphase, with mitotic Brn1. In lteΔ cells Brn1 release was delayed, even at temperatures that do not impair mitotic exit. Mutations in MEN pathway components that act downstream of Lte1 similarly delayed rDNA decompaction. We found that Brn1 release in wild-type cells coincided with the release of Cdc14 phosphatase from the nucleolus and with mitotic CDK inactivation, yet it could be selectively delayed by perturbation of the MEN pathway. This may argue that different levels of Cdk inactivation control spindle disassembly and chromatin decompaction. Mutation of lte1 also impaired rotation of the nucleus in early G1.

The kinesin-14 Klp2 is negatively regulated by the SIN for proper spindle elongation and telophase nuclear positioning

Mana-Capelli, Sebastian; McLean, Janel R.; Chen, Chun-Ti; Gould, Kathleen L.; McCollum, Dannel
Fonte: The American Society for Cell Biology Publicador: The American Society for Cell Biology
Tipo: Artigo de Revista Científica
Publicado em 01/12/2012 EN
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The SIN signaling pathway promotes cytokinesis and other late mitotic events. The terminal SIN kinase, Sid2, phosphorylates the kinesin-14 protein Klp2 to remove it from microtubules, which is important for efficient anaphase spindle elongation and telophase nuclear positioning.

Bcl-xL regulation and function in cell cycle checkpoints and progression

Wang, Jianfang
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
EN
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Quelques évidences suggèrent que Bcl-xL, un membre anti-apoptotique de la famille Bcl-2, possède également des fonctions au niveau du cycle cellulaire et de ses points-contrôle. Pour étudier la régulation et fonction de Bcl-xL au cours du cycle cellulaire, nous avons généré et exprimé dans des cellules humaines une série de mutants de phosphorylation incluant Thr41Ala, Ser43Ala, Thr47Ala, Ser49Ala, Ser56Ala, Ser62Ala et Thr115Ala. L'analyse de cette série de mutants révèle que les cellules exprimant Bcl-xL(Ser62Ala) sont moins stables au point-contrôle G2 du cycle cellulaire comparées aux cellules exprimant le type sauvage ou les autres mutants de phosphorylation incluant Thr41Ala, Ser43Ala, Thr47Ala, Ser56Ala et Thr115Ala. Les études de cinétiques de phosphorylation et de localisation de phospho-Bcl-xL(Ser62) dans des cellules synchronisées et suite à l'activation du point-contrôle en G2 médié par l'étoposide (VP16), nous indiquent que phospho-Bcl-xL(Ser62) migre dans les corps nucléolaires durant l'arrêt en G2 dans les cellules exposées au VP16. Une série d'expériences incluant des essais kinase in vitro, l'utilisation d'inhibiteurs pharmacologiques et d'ARN interférant, nous révèlent que Polo kinase 1 (PLK1) et MAPK9/JNK2 sont les protéines kinase impliquées dans la phosphorylation de Bcl-xL(Ser62)...

Drosophila homologs of mammalian TNF/TNFR-related molecules regulate segregation of Miranda/Prospero in neuroblasts

Wang, Huashan; Cai, Yu; Chia, William; Yang, Xiaohang
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
EN
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During neuroblast (NB) divisions, cell fate determinants Prospero (Pros) and Numb, together with their adaptor proteins Miranda (Mira) and Partner of Numb, localize to the basal cell cortex at metaphase and segregate exclusively to the future ganglion mother cells (GMCs) at telophase. In inscuteable mutant NBs, these basal proteins are mislocalized during metaphase. However, during anaphase/telophase, these mutant NBs can partially correct these earlier localization defects and redistribute cell fate determinants as crescents to the region where the future GMC ‘buds' off. This compensatory mechanism has been referred to as ‘telophase rescue'. We demonstrate that the Drosophila homolog of the mammalian tumor-necrosis factor (TNF) receptor-associated factor (DTRAF1) and Eiger (Egr), the homolog of the mammalian TNF, are required for telophase rescue of Mira/Pros. DTRAF1 localizes as an apical crescent in metaphase NBs and this apical localization requires Bazooka (Baz) and Egr. The Mira/Pros telophase rescue seen in inscuteable mutant NBs requires DTRAF1. Our data suggest that DTRAF1 binds to Baz and acts downstream of Egr in the Mira/Pros telophase rescue pathway.

The role of MEN (mitosis exit network) proteins in the cytokinesis of Saccharomyces cerevisiae; Función de las proteínas MEN ("mitosis exit network") en la citocinesis de Saccharomyces cerevisiae

Jiménez, Javier; Castelao, Beatriz A.; González-Novo, Alberto; Sánchez-Pérez, Miguel
Fonte: Sociedad Española de Microbiología; Springer Publicador: Sociedad Española de Microbiología; Springer
Tipo: Artículo
ENG
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[EN]: At the latest stages of their cell cycle, cells carry out crucial processes for the correct segregation of their genetic and cytoplasmic material. In this work, we provide evidence demonstrating that the cell cycle arrest of some MEN (mitosis exit network) mutants in the anaphase-telophase transition is bypassed. In addition, the ability of cdc15 diploid mutant strains to develop non-septated chains of cells, supported by nuclear division, is shown. This phenotype is also displayed by haploid cdc15 mutant strains when cell lysis is prevented by osmotic protection, and shared by other MEN mutants. By contrast, anaphase-telophase arrest is strictly observed in double MEN-FEAR (fourteen early anaphase release) mutants. In this context, the overexpression of a FEAR component, SPO12, in a MEN mutant background enhances the ability of MEN mutants to bypass cell cycle arrest. Taken together, these data suggest a critical role of Cdc15 and other MEN proteins in cytokinesis, allowing a new model for their cellular function to be proposed.; [ES]: En las últimas etapas de su ciclo celular, las células llevan a cabo procesos cruciales para la segregación correcta del material genético y citoplásmico. Es un tema de investigación de gran actualidad. En este trabajo aportamos pruebas que demuestran que en algunos mutantes MEN ("mitosis exit network") el ciclo celular no se detiene en la transición anafase-telofase. Además...

Multiple telophase arrest bypassed (tab) mutants alleviate the essential requirement for Cdc15 in exit from mitosis in S. cerevisiae

Shou, Wenying; Deshaies, Raymond J.
Fonte: Instituto de Tecnologia da Califórnia Publicador: Instituto de Tecnologia da Califórnia
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 12/03/2002
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Background: The Mitotic Exit Network (MEN) proteins – including the protein kinase Cdc15 and the protein phosphatase Cdc14 – are essential for exit from mitosis in Saccharomyces cerevisiae. To identify downstream targets of the MEN, we sought telophase arrest bypassed (tab) mutations that bypassed the essential requirement for CDC15. Previous studies identified net1tab2-1 and CDC14TAB6-1 as mutations in the RENT complex subunits Net1 and Cdc14, respectively, and revealed that the MEN acts by promoting release of Cdc14 from its nucleolar Net1 anchor during anaphase. However, the remaining tab mutants were not characterized. Results: Fourteen out of fifteen tab mutants were mapped to three recessive (tab1-tab3) and three dominant (TAB5-TAB7) linkage groups. We show that net1tab2-1 enables growth of tem1Δ, cdc15Δ, dbf2Δ dbf20Δ, and mob1Δ, but not cdc5Δ or cdc14Δ, arguing that whereas the essential task of the first four genes is to promote exit from mitosis, CDC5 possesses additional essential function(s). net1tab2-1 but not CDC14TAB6-1 resulted in a high rate of chromosome loss, indicating that Net1 promotes accurate chromosome segregation in addition to its multiple known roles. Finally, TAB1 was shown to be MTR10, a gene encoding nuclear transport receptor/adaptor. In some of the tab mutants including mtr10tab1-1...

The role of MEN (mitosis exit network) proteins in the cytokinesis of Saccharomyces cerevisiae

Jiménez,Javier; Castelao,Beatriz A.; González-Novo,Alberto; Sánchez-Pérez,Miguel
Fonte: International Microbiology Publicador: International Microbiology
Tipo: info:eu-repo/semantics/article; journal article; info:eu-repo/semantics/publishedVersion Formato: text/html; application/pdf
Publicado em 01/03/2005 ENG
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At the latest stages of their cell cycle, cells carry out crucial processes for the correct segregation of their genetic and cytoplasmic material. In this work, we provide evidence demonstrating that the cell cycle arrest of some MEN (mitosis exit network) mutants in the anaphase-telophase transition is bypassed. In addition, the ability of cdc15 diploid mutant strains to develop non-septated chains of cells, supported by nuclear division, is shown. This phenotype is also displayed by haploid cdc15 mutant strains when cell lysis is prevented by osmotic protection, and shared by other MEN mutants. By contrast, anaphase-telophase arrest is strictly observed in double MEN-FEAR (fourteen early anaphase release) mutants. In this context, the overexpression of a FEAR component, SPO12, in a MEN mutant background enhances the ability of MEN mutants to bypass cell cycle arrest. Taken together, these data suggest a critical role of Cdc15 and other MEN proteins in cytokinesis, allowing a new model for their cellular function to be proposed.