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  • 1
    Online Resource
    Online Resource
    TIME SEQUENCE OF NUCLEAR PORE FORMATION IN PHYTOHEMAGGLUTININ-STIMULATED LYMPHOCYTES AND IN H E L A CELLS DURING THE CELL CYCLE
    Rockefeller University Press ; 1972
    In:  The Journal of Cell Biology Vol. 55, No. 2 ( 1972-11-01), p. 433-447
    Details
    In: The Journal of Cell Biology, Rockefeller University Press, Vol. 55, No. 2 ( 1972-11-01), p. 433-447
    Abstract: The time sequence of nuclear pore frequency changes was determined for phytohemagglutinin (PHA)-stimulated human lymphocytes and for HeLa S-3 cells during the cell cycle. The number of nuclear pores/nucleus was calculated from the experimentally determined values of nuclear pores/µ2 and the nuclear surface. In the lymphocyte system the number of pores/nucleus approximately doubles during the 48 hr after PHA stimulation. The increase in pore frequency is biphasic and the first increase seems to be related to an increase in the rate of protein synthesis. The second increase in pores/nucleus appears to be correlated with the onset of DNA synthesis. In the HeLa cell system, we could also observe a biphasic change in pore formation. Nuclear pores are formed at the highest rate during the first hour after mitosis. A second increase in the rate of pore formation corresponds in time with an increase in the rate of nuclear acidic protein synthesis shortly before S phase. The total number of nuclear pores in HeLa cells doubles from ∼2000 in G1 to ∼4000 at the end of the cell cycle. The doubling of the nuclear volume and the number of nuclear pores might be correlated to the doubling of DNA content. Another correspondence with the nuclear pore number in S phase is found in the number of simultaneously replicating replication sites. This number may be fortuitous but leads to the rather speculative possibility that the nuclear pore might be the site of initiation and/or replication of DNA as well as the site of nucleocytoplasmic exchange. That is, the nuclear pore complex may have multiple functions.
    Type of Medium: Online Resource
    ISSN: 1540-8140 , 0021-9525
    URL: Article
    DOI: 10.1083/jcb.55.2.433
    RVK:
    WA 15000
    Language: English
    Publisher: Rockefeller University Press
    Publication Date: 1972
    detail.hit.zdb_id: 1421310-2
    SSG: 12
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  • 2
    Online Resource
    Online Resource
    Artefacts Occurring During Freeze-Etch Preparation
    Cambridge University Press (CUP) ; 1972
    In:  Proceedings, annual meeting, Electron Microscopy Society of America Vol. 30 ( 1972-08), p. 296-297
    Details
    In: Proceedings, annual meeting, Electron Microscopy Society of America, Cambridge University Press (CUP), Vol. 30 ( 1972-08), p. 296-297
    Abstract: Much effort has been put into the process to obtain undistorted biological specimens for use in electron microscopy. It has been well accepted that the main advantage of the freeze-etching method is to obtain cells stabilized in the living state. This method has proved to be a useful tool to study membrane structures. This communication deals with a number of artefacts which occur during the freeze-etching preparation. The effect of glycerol treatment as an anti-freeze agent on the cellular membranes has not yet been completely solved. The interpretation of results must take into account the physical treatment during the steps of preparation. In order to avoid decreased viability others have added glycerol incrementally; however, in some cases alterationsin cellular structure have been reported.
    Type of Medium: Online Resource
    ISSN: 0424-8201 , 2690-1315
    URL: Article
    DOI: 10.1017/S0424820100094747
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 1972
    SSG: 11
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  • 3
    Online Resource
    Online Resource
    Screening cDNA expression libraries with monoclonal and polyclonal antibodies using an amplified biotin-avidin-peroxidase technique
    Elsevier BV ; 1986
    In:  Analytical Biochemistry Vol. 156, No. 2 ( 1986-08), p. 417-423
    Details
    In: Analytical Biochemistry, Elsevier BV, Vol. 156, No. 2 ( 1986-08), p. 417-423
    Type of Medium: Online Resource
    ISSN: 0003-2697
    URL: Article
    DOI: 10.1016/0003-2697(86)90275-7
    Language: English
    Publisher: Elsevier BV
    Publication Date: 1986
    detail.hit.zdb_id: 1461105-3
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  • 4
    Online Resource
    Online Resource
    EFFECT OF METABOLIC INHIBITORS ON NUCLEAR PORE FORMATION DURING THE HELA S3 CELL CYCLE
    Rockefeller University Press ; 1973
    In:  The Journal of Cell Biology Vol. 59, No. 3 ( 1973-12-01), p. 669-676
    Details
    In: The Journal of Cell Biology, Rockefeller University Press, Vol. 59, No. 3 ( 1973-12-01), p. 669-676
    Abstract: The effect of various antimetabolites on nuclear pore formation was studied in synchronized HeLa S3 cells. The nuclear size was determined by light microscopy and the pore number per unit area of nuclear surface by the freeze-etching technique and electron microscopy. It was found that the inhibition of DNA replication or ribosomal RNA synthesis has no effect on nuclear size increase or pore formation. However, the inhibition of ATP synthesis effectively stops nuclear pore formation. Cycloheximide blocks nuclear pore formation at the same time during G1 phase of the cell cycle when nuclear size increase is blocked by high concentrations of actinomycin D. This suggests that certain proteins or other factors leading to pore formation and nuclear size increase are transcribed and synthesized at about 3–4 h after mitosis, i.e., about 1–2 h before S phase begins.
    Type of Medium: Online Resource
    ISSN: 1540-8140 , 0021-9525
    URL: Article
    DOI: 10.1083/jcb.59.3.669
    RVK:
    WA 15000
    Language: English
    Publisher: Rockefeller University Press
    Publication Date: 1973
    detail.hit.zdb_id: 1421310-2
    SSG: 12
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  • 5
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    Online Resource
    Heat shock and Cd2+ exposure regulate PML and Daxx release from ND10 by independent mechanisms that modify the induction of heat-shock proteins 70 and 25 differently
    The Company of Biologists ; 2003
    In:  Journal of Cell Science Vol. 116, No. 3 ( 2003-02-01), p. 513-524
    Details
    In: Journal of Cell Science, The Company of Biologists, Vol. 116, No. 3 ( 2003-02-01), p. 513-524
    Abstract: Nuclear domains called ND10 or PML bodies might function as nuclear depots by recruiting or releasing certain proteins. Although recruitment of proteins through interferon-induced upregulation and SUMO-1 modification level of PML had been defined, it is not known whether release of proteins is regulated and has physiological consequences. Exposure to sublethal environmental stress revealed a sequential release of ND10-associated proteins. Upon heat shock Daxx and Sp100 were released but PML remained, whereas exposure to subtoxic concentrations of CdCl2 induced the release of ND10-associated proteins, including PML, with Sp100 remaining in a few sites. In both cases,recovery times were similar and were followed by a burst of mitotic activity. Cadmium-induced release of proteins from ND10 could be blocked by inhibiting activation of p38 MAPK or ERK1/2. By contrast, heat-shock-induced desumolation of PML and release of proteins from ND10 are unaffected by these inhibitors but can be recapitulated by overexpression of the SUMO isopeptidase SENP-1. Therefore, activation of SENP-1-like SUMO isopeptidase(s) during heat shock is not affected by these kinases. Thus, the release of ND10-associated proteins is not due to a general dispersal of nuclear domains but seems to be regulated by rapid desumolation during thermal stress and through the phosphorylation cascade of stress and mitogenic signaling pathways in the case of CdCl2. Whether the release of certain proteins had consequences was tested for heat-shock-protein transcription and synthesis. Release of Daxx correlated with Hsp25 suppression, suggesting that Daxx normally inhibits immediate Hsp25 production. Release of PML correlated with lower production of Hsp70. These results suggest that segregation or release of PML or Daxx have differential physiological relevance during the stress response. The fact that enzymatic activation of protein release or segregation after stress modifies the heat-shock response strengthens the concept of ND10 as a regulated depot of effector proteins.
    Type of Medium: Online Resource
    ISSN: 1477-9137 , 0021-9533
    URL: Article
    DOI: 10.1242/jcs.00253
    Language: English
    Publisher: The Company of Biologists
    Publication Date: 2003
    detail.hit.zdb_id: 219171-4
    detail.hit.zdb_id: 1483099-1
    SSG: 12
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  • 6
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    Online Resource
    Differential Role of Sp100 Isoforms in Interferon-Mediated Repression of Herpes Simplex Virus Type 1 Immediate-Early Protein Expression
    American Society for Microbiology ; 2006
    In:  Journal of Virology Vol. 80, No. 16 ( 2006-08-15), p. 8019-8029
    Details
    In: Journal of Virology, American Society for Microbiology, Vol. 80, No. 16 ( 2006-08-15), p. 8019-8029
    Abstract: Nuclear domains called ND10 or PML nuclear bodies contain interferon (IFN)-upregulated proteins like PML and Sp100. Paradoxically, herpes simplex virus 1 (HSV-1) begins its transcriptional cascade at aggregates of ND10-associated proteins, which in turn are destroyed by the HSV-1 immediate-early protein ICP0. While PML is essential in the formation of ND10, the function of Sp100 in the cells' defense against viral infection is unknown. In this study we investigated the potential antiviral effect of IFN-β-induced Sp100. We found that IFN-β treatment leads to a differential accumulation of four Sp100 isoforms in different cell lines. Using an HEK293 cell line derivative, 293-S, producing no detectable amounts of Sp100 even after IFN exposure, we analyzed individual Sp100 isoforms for their effect on HSV-1 infection. Sp100 isoforms B, C, and HMG, but not Sp100A, suppressed ICP0 and ICP4 early after infection. Isoforms B, C, and HMG suppressed expression from the ICP0 promoter in transient transfection, whereas Sp100A enhanced expression. Moreover, Sp100A localized in ND10, whereas the repressive isoforms were either dispersed within the nucleus or, at unphysiologically higher expression levels, formed new aggregates. The repressive activity was dependent on an intact SAND domain, since Sp100B bearing a W655Q mutation in the SAND domain lost this repressive activity and accumulated in ND10. Using RNA interference to knock down the repressive Sp100 isoforms B, C, and HMG, we find that they are an essential part of the IFN-β-mediated suppression of ICP0 expression. These data suggest that repression by the Sp100 isoforms B, C, and HMG takes place outside of ND10 and raise the possibility that viral genomes at Sp100A accumulations are more likely to start their transcription program because of a more permissive local environment.
    Type of Medium: Online Resource
    ISSN: 0022-538X , 1098-5514
    URL: Article
    DOI: 10.1128/JVI.02164-05
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2006
    detail.hit.zdb_id: 1495529-5
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  • 7
    Online Resource
    Online Resource
    Differential Functions of Interferon-Upregulated Sp100 Isoforms: Herpes Simplex Virus Type 1 Promoter-Based Immediate-Early Gene Suppression and PML Protection from ICP0-Mediated Degradation
    American Society for Microbiology ; 2009
    In:  Journal of Virology Vol. 83, No. 10 ( 2009-05-15), p. 5168-5180
    Details
    In: Journal of Virology, American Society for Microbiology, Vol. 83, No. 10 ( 2009-05-15), p. 5168-5180
    Abstract: Cells have intrinsic defenses against virus infection, acting before the innate or the adaptive immune response. Preexisting antiviral proteins such as PML, Daxx, and Sp100 are stored in specific nuclear domains (ND10). In herpes simplex virus type 1 (HSV-1), the immediate-early protein ICP0 serves as a counterdefense through degradation of the detrimental protein PML. We asked whether interferon (IFN)-upregulated Sp100 is similarly antagonized by ICP0 in normal human fibroblasts by using a selective-knockdown approach. We find that of the four Sp100 isoforms, the three containing a SAND domain block the transcription of HSV-1 proteins ICP0 and ICP4 at the promoter level and that IFN changes the differential splicing of the Sp100 transcript in favor of the inhibitor Sp100C. At the protein level, ICP0 activity does not lead to the hydrolysis of any of the Sp100 isoforms. The SAND domain-containing isoforms are not general inhibitors of viral promoters, as the activity of the major immediate-early cytomegalovirus promoter is not diminished, whereas the long terminal repeat of a retrovirus, like the ICP0 promoter, is strongly inhibited. Since we could not find a specific promoter region in the ICP0 gene that responds to the SAND domain-containing isoforms, we questioned whether Sp100 could act through other antiviral proteins such as PML. We find that all four Sp100 isoforms stabilize ND10 and protect PML from ICP0-based hydrolysis. Loss of either all PML isoforms or all Sp100 isoforms reduces the opposite constituent ND10 protein, suggesting that various interdependent mechanisms of ND10-based proteins inhibit virus infection at the immediate-early level.
    Type of Medium: Online Resource
    ISSN: 0022-538X , 1098-5514
    URL: Article
    DOI: 10.1128/JVI.02083-08
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2009
    detail.hit.zdb_id: 1495529-5
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  • 8
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    Online Resource
    Sp100A promotes chromatin decondensation at a cytomegalovirus-promoter–regulated transcription site
    American Society for Cell Biology (ASCB) ; 2013
    In:  Molecular Biology of the Cell Vol. 24, No. 9 ( 2013-05), p. 1454-1468
    Details
    In: Molecular Biology of the Cell, American Society for Cell Biology (ASCB), Vol. 24, No. 9 ( 2013-05), p. 1454-1468
    Abstract: Promyelocytic leukemia nuclear bodies (PML-NBs)/nuclear domain 10s (ND10s) are nuclear structures that contain many transcriptional and chromatin regulatory factors. One of these, Sp100, is expressed from a single-copy gene and spliced into four isoforms (A, B, C, and HMG), which differentially regulate transcription. Here we evaluate Sp100 function in single cells using an inducible cytomegalovirus-promoter–regulated transgene, visualized as a chromatinized transcription site. Sp100A is the isoform most strongly recruited to the transgene array, and it significantly increases chromatin decondensation. However, Sp100A cannot overcome Daxx- and α-thalassemia mental retardation, X-linked (ATRX)–mediated transcriptional repression, which indicates that PML-NB/ND10 factors function within a regulatory hierarchy. Sp100A increases and Sp100B, which contains a SAND domain, decreases acetyl-lysine regulatory factor levels at activated sites, suggesting that Sp100 isoforms differentially regulate transcription by modulating lysine acetylation. In contrast to Daxx, ATRX, and PML, Sp100 is recruited to activated arrays in cells expressing the herpes simplex virus type 1 E3 ubiquitin ligase, ICP0, which degrades all Sp100 isoforms except unsumoylated Sp100A. The recruitment Sp100A(K297R), which cannot be sumoylated, further suggests that sumoylation plays an important role in regulating Sp100 isoform levels at transcription sites. This study provides insight into the ways in which viruses may modulate Sp100 to promote their replication cycles.
    Type of Medium: Online Resource
    ISSN: 1059-1524 , 1939-4586
    URL: Article
    DOI: 10.1091/mbc.e12-09-0669
    Language: English
    Publisher: American Society for Cell Biology (ASCB)
    Publication Date: 2013
    detail.hit.zdb_id: 1474922-1
    SSG: 12
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  • 9
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    Sp100 as a Potent Tumor Suppressor: Accelerated Senescence and Rapid Malignant Transformation of Human Fibroblasts through Modulation of an Embryonic Stem Cell Program
    American Association for Cancer Research (AACR) ; 2010
    In:  Cancer Research Vol. 70, No. 23 ( 2010-12-01), p. 9991-10001
    Details
    In: Cancer Research, American Association for Cancer Research (AACR), Vol. 70, No. 23 ( 2010-12-01), p. 9991-10001
    Abstract: Identifying the functions of proteins, which associate with specific subnuclear structures, is critical to understanding eukaryotic nuclear dynamics. Sp100 is a prototypical protein of ND10/PML nuclear bodies, which colocalizes with Daxx and the proto-oncogenic PML. Sp100 isoforms contain SAND, PHD, Bromo, and HMG domains and are highly sumoylated, all characteristics suggestive of a role in chromatin-mediated gene regulation. A role for Sp100 in oncogenesis has not been defined previously. Using selective Sp100 isoform-knockdown approaches, we show that normal human diploid fibroblasts with reduced Sp100 levels rapidly senesce. Subsequently, small rapidly dividing Sp100 minus cells emerge from the senescing fibroblasts and are found to be highly tumorigenic in nude mice. The derivation of these tumorigenic cells from the parental fibroblasts is confirmed by microsatellite analysis. The small rapidly dividing Sp100 minus cells now also lack ND10/PML bodies, and exhibit genomic instability and p53 cytoplasmic sequestration. They have also activated MYC, RAS, and TERT pathways and express mesenchymal to epithelial transdifferentiation (MET) markers. Reintroduction of expression of only the Sp100A isoform is sufficient to maintain senescence and to inhibit emergence of the highly tumorigenic cells. Global transcriptome studies, quantitative PCR, and protein studies, as well as immunolocalization studies during the course of the transformation, reveal that a transient expression of stem cell markers precedes the malignant transformation. These results identify a role for Sp100 as a tumor suppressor in addition to its role in maintaining ND10/PML bodies and in the epigenetic regulation of gene expression. Cancer Res; 70(23); 9991–10001. ©2010 AACR.
    Type of Medium: Online Resource
    ISSN: 0008-5472 , 1538-7445
    URL: Article
    DOI: 10.1158/0008-5472.CAN-10-1483
    RVK:
    XA 36000
    RVK:
    XA 10000
    Language: English
    Publisher: American Association for Cancer Research (AACR)
    Publication Date: 2010
    detail.hit.zdb_id: 2036785-5
    detail.hit.zdb_id: 1432-1
    detail.hit.zdb_id: 410466-3
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  • 10
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    Pml Is Critical for Nd10 Formation and Recruits the Pml-Interacting Protein Daxx to This Nuclear Structure When Modified by Sumo-1
    Rockefeller University Press ; 1999
    In:  The Journal of Cell Biology Vol. 147, No. 2 ( 1999-10-18), p. 221-234
    Details
    In: The Journal of Cell Biology, Rockefeller University Press, Vol. 147, No. 2 ( 1999-10-18), p. 221-234
    Abstract: Nuclear domain 10 (ND10), also referred to as nuclear bodies, are discrete interchromosomal accumulations of several proteins including promyelocytic leukemia protein (PML) and Sp100. In this study, we investigated the mechanism of ND10 assembly by identifying proteins that are essential for this process using cells lines that lack individual ND10-associated proteins. We identified the adapter protein Daxx and BML, the RecQ helicase missing in Bloom syndrome, as new ND10-associated proteins. PML, but not BLM or Sp100, was found to be responsible for the proper localization of all other ND10-associated proteins since they are dispersed in PML−/− cells. Introducing PML into this cell line by transient expression or fusion with PML-producing cells recruited ND10-associated proteins into de novo formed ND10 attesting to PMLs essential nature in ND10 formation. In the absence of PML, Daxx is highly enriched in condensed chromatin. Its recruitment to ND10 from condensed chromatin requires a small ubiquitin-related modifier (SUMO-1) modification of PML and reflects the interaction between the COOH-terminal domain of Daxx and PML. The segregation of Daxx from condensed chromatin in the absence of PML to ND10 by increased accumulation of SUMO-1–modified PML suggests the presence of a variable equilibrium between these two nuclear sites. Our findings identify the basic requirements for ND10 formation and suggest a dynamic mechanism for protein recruitment to these nuclear domains controlled by the SUMO-1 modification state of PML.
    Type of Medium: Online Resource
    ISSN: 0021-9525 , 1540-8140
    URL: Article
    DOI: 10.1083/jcb.147.2.221
    RVK:
    WA 15000
    Language: English
    Publisher: Rockefeller University Press
    Publication Date: 1999
    detail.hit.zdb_id: 1421310-2
    SSG: 12
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