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  • 1
    Electronic Resource
    Electronic Resource
    Centromeric inactivation in a dicentric human Y;21 translocation chromosome (1997)
    Springer
    Chromosoma 106 (1997), S. 199-206 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract.  A de novo dicentric Y;21 (q11.23;p11) translocation chromosome with one of its two centromeres inactive has provided the opportunity to study the relationship between centromeric inactivation, the organization of alphoid satellite DNA and the distribution of CENP-C. The proband, a male with minor features of Down’s syndrome, had a major cell line with 45 chromosomes including a single copy of the translocation chromosome, and a minor one with 46 chromosomes including two copies of the translocation chromosome and hence effectively trisomic for the long arm of chromosome 21. Centromeric activity as defined by the primary constriction was variable: in most cells with a single copy of the Y;21 chromosome, the Y centromere was inactive. In the cells with two copies, one copy had an active Y centromere (chromosome 21 centromere inactive) and the other had an inactive Y centromere (chromosome 21 centromere active). Three different partial deletions of the Y alphoid array were found in skin fibroblasts and one of these was also present in blood. Clones of single cell origin from fibroblast cultures were analysed both for their primary constriction and to characterise their alphoid array. The results indicate that (1) each clone showed a fixed pattern of centromeric activity; (2) the alphoid array size was stable within a clone; and (3) inactivation of the Y centromere was associated with both full-sized and deleted alphoid arrays. Selected clones were analysed with antibodies to CENP-C, and staining was undetectable at both intact and deleted arrays of the inactive Y centromeres. Thus centromeric inactivation appears to be largely an epigenetic event.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004120050240
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  • 2
    Electronic Resource
    Electronic Resource
    Localization of CENP-E in the fibrous corona and outer plate of mammalian kinetochores from prometaphase through anaphase (1997)
    Springer
    Chromosoma 106 (1997), S. 446-455 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract.  We have conducted a detailed ultrastructural analysis of the distribution of the kinesin-related centromere protein CENP-E during mitosis in cultured human, rat kangaroo and Indian muntjac cells. Using an affinity-purified polyclonal antibody and detection by 0.8 nm colloidal gold particles, CENP-E was localized primarily to the fibrous corona of the kinetochore in prometaphase and metaphase cells. Some labeling of the kinetochore outer plate was also observed. The distribution of fibrous corona-associated CENP-E did not change dramatically following the attachment of microtubules to the kinetochore. Thus, the normal disappearance of this kinetochore substructure in conventional electron micrographs of mitotic chromosomes with attached kinetochores is not due to the corona becoming stretched along the spindle microtubules as has been suggested. Examination of cells undergoing anaphase chromatid movement revealed the presence of CENP-E still associated with the outer surface of the kinetochore plate. At the same time, the majority of detectable CENP-E in these cells was associated with the bundles of antiparallel microtubules in the central spindle. CENP-E in this region of the cell is apparently associated with the stem body matrix material. The simultaneous localization of CENP-E on centromeres and the central spindle during anaphase was confirmed by both wide-field microscopy of human cells and conventional fluorescence microscopy of rat kangaroo cells. Together, the observations reported here are consistent with models in which CENP-E has a role in promoting the poleward migration of sister chromatids during anaphase A.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004120050266
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  • 3
    Electronic Resource
    Electronic Resource
    A neocentromere in the DAZ region of the human Y chromosome (2000)
    Springer
    Chromosoma 109 (2000), S. 318-327 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. We describe a novel rearranged human Y chromosome consisting of an inverted duplication of the long arm heterochromatin and a small amount of euchromatin: rea(Y)(qter–q11.2::q11.2–qter). The normal centromere has been deleted and a neocentromere containing CENP-A, -C, -E and Mad2 but not CENP-B has formed close to the breakpoint. A 2.7 Mb yeast artificial chromosome contig spanning the breakpoint was constructed and the breakpoint was localised to a region of 〈120 kb close to the DAZ gene cluster. Combined immunofluorescence and fluorescence in situ hybridisation showed that the centromeric protein-binding domain of the neocentromere was located near the breakpoint and within the DAZ cluster.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004120000081
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  • 4
    Electronic Resource
    Electronic Resource
    MAMMALIAN CASPASES: Structure, Activation, Substrates, and Functions During Apoptosis (1999)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Biochemistry 68 (1999), S. 383-424 
    Details
    ISSN: 0066-4154
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Chemistry and Pharmacology , Biology
    Notes: Abstract Apoptosis is a genetically programmed, morphologically distinct form of cell death that can be triggered by a variety of physiological and pathological stimuli. Studies performed over the past 10 years have demonstrated that proteases play critical roles in initiation and execution of this process. The caspases, a family of cysteine-dependent aspartate-directed proteases, are prominent among the death proteases. Caspases are synthesized as relatively inactive zymogens that become activated by scaffold-mediated transactivation or by cleavage via upstream proteases in an intracellular cascade. Regulation of caspase activation and activity occurs at several different levels: (a) Zymogen gene transcription is regulated; (b) antiapoptotic members of the Bcl-2 family and other cellular polypeptides block proximity-induced activation of certain procaspases; and (c) certain cellular inhibitor of apoptosis proteins (cIAPs) can bind to and inhibit active caspases. Once activated, caspases cleave a variety of intracellular polypeptides, including major structural elements of the cytoplasm and nucleus, components of the DNA repair machinery, and a number of protein kinases. Collectively, these scissions disrupt survival pathways and disassemble important architectural components of the cell, contributing to the stereotypic morphological and biochemical changes that characterize apoptotic cell death.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.biochem.68.1.383
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  • 5
    Electronic Resource
    Electronic Resource
    Nucleosome assembly (1980)
    [s.l.] : Nature Publishing Group
    Nature 286 (1980), S. 763-767 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Histones and DNA can spontaneously associate to form the nucleosome subunits of eukaryotic chromatin, but two proteins which occur in the eukaryotic nucleus can facilitate nucleosome assembly and greatly extend the conditions which permit assembly to occur. Recently several laboratories have ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/286763a0
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  • 6
    Electronic Resource
    Electronic Resource
    Apoptosis A cellular poison cupboard (1999)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 397 (1999), S. 387-389 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Apoptotic cell death is spectacular — one moment a cell looks peaceful and happy, the next it enters a violent programme of cytoplasmic blebbing worthy of the death throes of an actor in a B-movie. One fascinating aspect of apoptosis is that virtually all cells contain latent forms of the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/17015
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  • 7
    Electronic Resource
    Electronic Resource
    Disruption of CENP antigen function perturbs dynein anchoring to the mitotic kinetochore (1996)
    Springer
    Chromosoma 104 (1996), S. 551-560 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Injection of purified autoantibodies against human centromeric proteins into HeLa cells during interphase disrupts the organization of the kinetochore and interferes with chromosomal movements during the subsequent mitosis even though the chromosomes retain the ability to bind microtubules. We have investigated the hypothesis that this phenotype arises from effects on cytoplasmic dynein, the microtubule motor protein. In previous experiments we found that introduction of anticentromere antibodies into cell nuclei during the G1- or S-phases causes a prometaphase-like arrest, while injections during G2-phase cause a metaphase arrest. We show here that, in both cases, the level of detectable cytoplasmic dynein at kinetochores is significantly decreased. In contrast, when injected cells were permitted to enter mitosis in the absence of microtubules (conditions where trilaminar kinetochores could be detected by electron microscopy), the intensity of dynein labeling on the kinetochores was identical to that seen in uninjected control cells exposed to colcemid. Therefore, the loss of dynein label on mitotic kinetochores was correlated both with the injection of anticentromere antibodies and with the presence of intact spindle microtubules. We suggest that the injection of anticentromere antibodies somehow weakens the association of dynein with the kinetochore, so that when microtubules are present, these motor molecules are pulled away from the kinetochores as they generate force. This model offers an explanation for the failure of chromosomes of injected cells to move normally in mitosis even though they have attached microtubules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00352295
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  • 8
    Electronic Resource
    Electronic Resource
    Disruption of CENP antigen function perturbs dynein anchoring to the mitotic kinetochore (1996)
    Springer
    Chromosoma 104 (1996), S. 551-560 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Injection of purified autoantibodies against human centromeric proteins into HeLa cells during interphase disrupts the organization of the kinetochore and interferes with chromosomal movements during the subsequent mitosis even though the chromosomes retain the ability to bind microtubules. We have investigated the hypothesis that this phenotype arises from effects on cytoplasmic dynein, the microtubule motor protein. In previous experiments we found that introduction of anticentromere antibodies into cell nuclei during the G1- or S-phases causes a prometaphase-like arrest, while injections during G2-phase cause a metaphase arrest. We show here that, in both cases, the level of detectable cytoplasmic dynein at kinetochores is significantly decreased. In contrast, when injected cells were permitted to enter mitosis in the absence of microtubules (conditions where trilaminar kinetochores could be detected by electron microscopy), the intensity of dynein labeling on the kinetochores was identical to that seen in uninjected control cells exposed to colcemid. Therefore, the loss of dynein label on mitotic kinetochores was correlated both with the injection of anticentromere antibodies and with the presence of intact spindle microtubules. We suggest that the injection of anticentromere antibodies somehow weakens the association of dynein with the kinetochore, so that when microtubules are present, these motor molecules are pulled away from the kinetochores as they generate force. This model offers an explanation for the failure of chromosomes of injected cells to move normally in mitosis even though they have attached microtubules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00352295
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  • 9
    Electronic Resource
    Electronic Resource
    Chromosomal passengers: Toward an integrated view of mitosis (1991)
    Springer
    Chromosoma 100 (1991), S. 139-146 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Conclusions The immunocytochemical “taxonomy” experiments cited above have identified a class of “chromosomal” antigens whose properties were not predicted by earlier models of mitosis. Our theory describing one possible explanation for the transfer of these antigens from the chromosomes to the spindle midzone at the metaphase: anaphase transition must now be subjected to further experimental tests. The phenotypes of cells microinjected with antibodies to passenger proteins should enable us to identify mitotic processes dependent on these proteins, as in the example of CHO1 antibody blocking mitotic progression (Nislow et al. 1990). In addition, the availability of cDNA clones and high titer antibodies may enable homologues of these components to be identified in organisms in which they can be subjected to genetic analysis. For the time being, we suggest that current views of the relative roles of chromosomes and cytoskeletal components in mitosis may require revision. Our hypothesis takes the current model for the role of the kinetochores in organizing the bipolar mitotic spindle (Kirschner and Mitchison 1986) a step further. The process of assembling a functional spindle and positioning the cleavage furrow may entail a degree of functional cooperation between chromosomes and cytoskeletal components far beyond that envisioned before now.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00337241
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  • 10
    Electronic Resource
    Electronic Resource
    Visualization of centromere proteins CENP-B and CENP-C on a stable dicentric chromosome in cytological spreads (1989)
    Springer
    Chromosoma 98 (1989), S. 1-12 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We have screened for the presence of two centromere autoantigens, CENP-B (80 kDa) and CENP-C (140 kDa) at the inactive centromere of a naturally occurring stable dicentric chromosome using specific antibodies that do not cross-react with any other chromosomal proteins. In order to discriminate between the active and inactive centromeres on this chromosome we have developed a modification of the standard methanol/acetic acid fixation procedure that allows us to obtain high-quality cytological spreads that retain antigenicity with the anti-centromere antibodies. We have noted three differences in the immunostaining patterns with specific anti-CENP-B and CENP-C antibodies. (1) The amount of detectable CENP-B varies from chromosome to chromosome. The amount of CENPC appears to be more or less the same on all chromosomes. (2) CENP-B is present at both active and inactive centromeres of stable dicentric autosomes. CENP-C is not detectable at the inactive centromeres. (3) While immunofluorescence with anti-CENP-C antibodies typically gives two discrete spots, staining with anti-CENP-B often appears as a single bright bar connecting both sister centromeres. This suggests that while CENP-C may be confined to the outer centromere in the kinetochore region, CENP-B may be distributed throughout the entire centromere. Our data suggest that CENP-C is likely to be a component of some invariant chromosomal substructure, such as the kinetochore. CENPB may be involved in some other aspect of centromere function, such as chromosome movement or DNA packaging.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00293329
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