Distribution of a thiophosphorylated spindle midzone antigen during spindle reactivation in vitro

1989 ◽  
Vol 93 (2) ◽  
pp. 279-285
Author(s):  
LINDA WORDEMAN ◽  
H. MASUDA ◽  
W. Z. CANDE
Keyword(s):  
Monoclonal Antibody ◽  
Mitotic Spindles ◽  
Associated Proteins ◽  
Spindle Midzone ◽  
Spindle Elongation

Mitotic spindles isolated from the diatom Stephanopyxis turris will elongate in vitro in the presence of ATP with a concurrent decrease in the width of the zone of microtubule overlap. A spindle-associated phosphoprotein that co-localizes with the zone of microtubule overlap in isolated spindles serves as a convenient marker for midzone-associated proteinsother than microtubules. We have used a monoclonal antibody that labels this protein when it is artificially thiophosphorylated and studied its redistribution during spindle reactivation in vitro. As the spindle elongates midzone label accumulates in a successively narrower and brighter ring at the spindle midpoint with increasing time in ATP. Biotinylated bovine microtubule segments polymerized onto the ends of the diatom microtubules increase the overall width of the zone of microtubule overlap and serve as a marker for the boundary of the original diatom overlap zone. During elongation in ATP, the biotinylated segments move into the area marked by the monoclonal antibody, which does not decrease in width until the spindle has elongated to the point at which the zone of microtubule overlap delineated by the newly polymerized microtubules is smaller than the original overlap zone. We use these results to develop a model to explain the behaviour of nonmicrotubule midzone-associated proteins during spindle elongation.

scholarly journals The molecular function of Ase1p

2003 ◽  
Vol 160 (4) ◽  
pp. 517-528 ◽  
Author(s):  
Scott C. Schuyler ◽  
Jenny Y. Liu ◽  
David Pellman
Keyword(s):  
Lateral Diffusion ◽  
Size Exclusion ◽  
Velocity Sedimentation ◽  
Exclusion Chromatography ◽  
Associated Proteins ◽  
Spindle Disassembly ◽  
Spindle Midzone ◽  
Spindle Elongation ◽  
And Function

The midzone is the domain of the mitotic spindle that maintains spindle bipolarity during anaphase and generates forces required for spindle elongation (anaphase B). Although there is a clear role for microtubule (MT) motor proteins at the spindle midzone, less is known about how microtubule-associated proteins (MAPs) contribute to midzone organization and function. Here, we report that budding yeast Ase1p is a member of a conserved family of midzone-specific MAPs. By size exclusion chromatography and velocity sedimentation, both Ase1p in extracts and purified Ase1p behaved as a homodimer. Ase1p bound and bundled MTs in vitro. By live cell microscopy, loss of Ase1p resulted in a specific defect: premature spindle disassembly in mid-anaphase. Furthermore, when overexpressed, Ase1p was sufficient to trigger spindle elongation in S phase–arrested cells. FRAP revealed that Ase1p has both a very slow rate of turnover within the midzone and limited lateral diffusion along spindle MTs. We propose that Ase1p functions as an MT cross-bridge that imparts matrix-like characteristics to the midzone. MT-dependent networks of spindle midzone MAPs may be one molecular basis for the postulated spindle matrix.

The RAV12 Monoclonal Antibody Recognizes the N-Linked Glycotope RAAG12: Expression in Human Normal and Tumor Tissues

2009 ◽  
Vol 133 (9) ◽  
pp. 1403-1412
Author(s):  
Suzanne K. Coberly ◽  
Francine Z. Chen ◽  
Mark P. Armanini ◽  
Yan Chen ◽  
Peter F. Young ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Antigen Expression ◽  
Subcellular Location ◽  
Carbohydrate Antigen ◽  
Cytoplasmic Staining ◽  
Safety Issues ◽  
Normal Tissues ◽  
Tumor Tissues ◽  
Associated Proteins

Abstract Context.—RAAG12 is a primate-restricted N-linked carbohydrate antigen present on multiple membrane-associated proteins. RAAG12 is recognized by the RAV12 monoclonal antibody. RAV12 binds to RAAG12-expressing gastrointestinal adenocarcinomas, modifies growth factor-mediated signaling, induces oncotic cell death in vitro, and has antitumor activity toward gastrointestinal tumor xenografts. Objective.—To determine the expression pattern of RAAG12 in normal and tumor tissue to identify indications for clinical study and potential safety issues. Design.—Immunohistochemistry of 36 normal human tissues and a broad range of tumor tissues to profile RAAG12 expression. Results.—More than 90% of colon, gastric, and pancreatic adenocarcinomas expressed RAAG12, and expression was uniform in most samples. Expression of RAAG12 at lower frequency and/or uniformity was observed in other cancers, including esophageal, ovarian, liver, breast, and prostate carcinomas and adenocarcinomas. Similar RAAG12 expression was observed between primary and metastatic colon adenocarcinomas. No staining was seen on cardiovascular, endocrine, neuromuscular, hematopoietic, or nervous system tissue from non–tumor-bearing individuals. RAAG12 was expressed on mucosal and glandular/ductal epithelium. The gastrointestinal tract mucosa and pancreatic/biliary ducts displayed the most uniform reactivity. RAAG12 exhibited differential subcellular localization in these normal, compared with tumor, tissues. Normal polarized epithelia primarily displayed apical membrane and cytoplasmic staining, whereas tumors exhibited whole membrane staining that increased with decreasing differentiation. Conclusions.—High expression of RAAG12 on tumors of gastrointestinal origin suggests these cancers are appropriate targets for RAV12 therapy. Differential subcellular location of RAAG12 on normal epithelia may limit accessibility of RAV12 to the subset of normal tissues that exhibit antigen expression.

scholarly journals Physiological and ultrastructural analysis of elongating mitotic spindles reactivated in vitro.

1986 ◽  
Vol 103 (2) ◽  
pp. 593-604 ◽  
Author(s):  
W Z Cande ◽  
K McDonald
Keyword(s):  
Cross Sections ◽  
Simple Procedure ◽  
Ultrastructural Level ◽  
Mitotic Spindles ◽  
Gap Formation ◽  
Microtubule Depolymerization ◽  
Central Spindle ◽  
Original Number ◽  
Spindle Elongation

We have developed a simple procedure for isolating mitotic spindles from the diatom Stephanopyxis turris and have shown that they undergo anaphase spindle elongation in vitro upon addition of ATP. The isolated central spindle is a barrel-shaped structure with a prominent zone of microtubule overlap. After ATP addition greater than 75% of the spindle population undergoes distinct structural rearrangements: the spindles on average are longer and the two half-spindles are separated by a distinct gap traversed by only a small number of microtubules, the phase-dense material in the overlap zone is gone, and the peripheral microtubule arrays have depolymerized. At the ultrastructural level, we examined serial cross-sections of spindles after 1-, 5-, and 10-min incubations in reactivation medium. Microtubule depolymerization distal to the poles is confirmed by the increased number of incomplete, i.e., c-microtubule profiles specifically located in the region of overlap. After 10 min we see areas of reduced microtubule number which correspond to the gaps seen in the light microscope and an overall reduction in the number of half-spindle microtubules to about one-third the original number. The changes in spindle structure are highly specific for ATP, are dose-dependent, and do not occur with nonhydrolyzable nucleotide analogues. Spindle elongation and gap formation are blocked by 10 microM vanadate, equimolar mixtures of ATP and AMPPNP, and by sulfhydryl reagents. This process is not affected by nocodazole, erythro-9-[3-(2-hydroxynonyl)]adenine, cytochalasin D, and phalloidin. In the presence of taxol, the extent of spindle elongation is increased; however, distinct gaps still form between the two half-spindles. These results show that the response of isolated spindles to ATP is a complex process consisting of several discrete steps including initiation events, spindle elongation mechanochemistry, controlled central spindle microtubule plus-end depolymerization, and loss of peripheral microtubules. They also show that the microtubule overlap zone is an important site of ATP action and suggest that spindle elongation in vitro is best explained by a mechanism of microtubule-microtubule sliding. Spindle elongation in vitro cannot be accounted for by cytoplasmic forces pulling on the poles or by microtubule polymerization.

scholarly journals UNC-45A is preferentially expressed in epithelial cells and binds to and co-localizes with interphase MTs

2019 ◽  
Author(s):  
Juri Habicht ◽  
Ashley Mooneyham ◽  
Mihir Shetty ◽  
Xiaonan Zhang ◽  
Vijayalakshmi Shridhar ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Ovarian Cancer Cells ◽  
Mitotic Spindles ◽  
Cellular Processes ◽  
Interphase Cells ◽  
Associated Proteins ◽  
Chemotherapeutic Treatment

AbstractUNC-45A is a ubiquitously expressed protein highly conserved throughout evolution. Most of what we currently know about UNC-45A pertains to its role as a regulator of the actomyosin system. However, emerging studies from both our and other laboratories support a role of UNC-45A outside of actomyosin regulation. This includes studies showing that UNC-45A: regulates gene transcription, co-localizes and biochemically co-fractionates with gamma tubulin and regulates centrosomal positioning, is found in the same subcellular fractions where MT-associated proteins are, and is a mitotic spindle-associated protein with MT destabilizing activity in absence of the actomyosin system.Here, we extended our previous findings and show that UNC45A is variably expressed across a spectrum of cell lines with the highest level being found in HeLa cells and in ovarian cancer cells inherently paclitaxel-resistant. Furthermore, we show that UNC-45A is preferentially expressed in epithelial cells, localizes to mitotic spindles in clinical tumor specimens of cancer and co-localizes and co-fractionates with MTs in interphase cells independent of actin or myosin.In sum, we report alteration of UNC45A localization in the setting of chemotherapeutic treatment of cells with paclitaxel, and localization of UNC45A to MTs both in vitro and in vivo. These findings will be important to ongoing and future studies in the field that further identify the important role of UNC45A in cancer and other cellular processes.

scholarly journals Three-dimensional structure of the central mitotic spindle of Diatoma vulgare.

1979 ◽  
Vol 83 (2) ◽  
pp. 428-442 ◽  
Author(s):  
J R McIntosh ◽  
K L McDonald ◽  
M K Edwards ◽  
B M Ross
Keyword(s):  
Three Dimensional ◽  
Three Dimensions ◽  
Dimensional Structure ◽  
Mitotic Spindles ◽  
Stereo Images ◽  
Central Spindle ◽  
Spindle Poles ◽  
Length Changes ◽  
Spindle Elongation

Central mitotic spindles in Diatoma vulgare have been investigated using serial sections and electron microscopy. Spindles at both early stages (before metaphase) and later stages of mitosis (metaphase to telophase) have been analyzed. We have used computer graphics technology to facilitate the analysis and to produce stereo images of the central spindle reconstructed in three dimensions. We find that at prometaphase, when the nuclear envelope is dissassembling, the spindle is constructed from two sets of polar microtubules (MTs) that interdigitate to form a zone of overlap. As the chromosomes become organized into the metaphase configuration, the polar MTs, the spindle, and the zone of overlap all elongate, while the number of MTs in the central spindle decreases from greater than 700 to approximately 250. Most of the tubules lost are short ones that reside near the spindle poles. The previously described decrease in the length of the zone of overlap during anaphase central spindle elongation is clearly demonstrated in stereo images. In addition, we have used our three-dimensional data to determine the lengths of the spindle MTs at various times during mitotis. The distribution of lengths is bimodal during prometaphase, but the short tubules disappear and the long tubules elongate as mitosis proceeds. The distributions of MT lengths are compared to the length distributions of MTs polymerized in vitro, and a model is presented to account for our findings about both MT length changes and microtubule movements.

scholarly journals Two Microtubule-associated Proteins of Arabidopsis MAP65s Promote Antiparallel Microtubule Bundling

2008 ◽  
Vol 19 (10) ◽  
pp. 4534-4544 ◽  
Author(s):  
Jérémie Gaillard ◽  
Emmanuelle Neumann ◽  
Daniel Van Damme ◽  
Virginie Stoppin-Mellet ◽  
Christine Ebel ◽  
...  
Keyword(s):  
Preprophase Band ◽  
Spindle Microtubule ◽  
Microtubule Associated Proteins ◽  
Late Anaphase ◽  
Associated Proteins ◽  
Planar Network ◽  
Spindle Midzone ◽  
Spindle Microtubules

The Arabidopsis MAP65s are a protein family with similarity to the microtubule-associated proteins PRC1/Ase1p that accumulate in the spindle midzone during late anaphase in mammals and yeast, respectively. Here we investigate the molecular and functional properties of AtMAP65-5 and improve our understanding of AtMAP65-1 properties. We demonstrate that, in vitro, both proteins promote the formation of a planar network of antiparallel microtubules. In vivo, we show that AtMAP65-5 selectively binds the preprophase band and the prophase spindle microtubule during prophase, whereas AtMAP65-1-GFP selectively binds the preprophase band but does not accumulate at the prophase spindle microtubules that coexists within the same cell. At later stages of mitosis, AtMAP65-1 and AtMAP65-5 differentially label the late spindle and phragmoplast. We present evidence for a mode of action for both proteins that involves the binding of monomeric units to microtubules that “zipper up” antiparallel arranged microtubules through the homodimerization of the N-terminal halves when adjacent microtubules encounter.

scholarly journals Poleward microtubule flux mitotic spindles assembled in vitro.

1991 ◽  
Vol 112 (5) ◽  
pp. 941-954 ◽  
Author(s):  
K E Sawin ◽  
T J Mitchison
Keyword(s):  
Mitotic Spindle ◽  
Preceding Paper ◽  
Mitotic Spindles ◽  
Microtubule Motor ◽  
Mitotic Spindle Assembly ◽  
Spindle Elongation ◽  
Dynamic Structures ◽  
Poleward Flux

In the preceding paper we described pathways of mitotic spindle assembly in cell-free extracts prepared from eggs of Xenopus laevis. Here we demonstrate the poleward flux of microtubules in spindles assembled in vitro, using a photoactivatable fluorescein covalently coupled to tubulin and multi-channel fluorescence videomicroscopy. After local photoactivation of fluorescence by UV microbeam, we observed poleward movement of fluorescein-marked microtubules at a rate of 3 microns/min, similar to rates of chromosome movement and spindle elongation during prometaphase and anaphase. This movement could be blocked by the addition of millimolar AMP-PNP but was not affected by concentrations of vanadate up to 150 microM, suggesting that poleward flux may be driven by a microtubule motor similar to kinesin. In contrast to previous results obtained in vivo (Mitchison, T. J. 1989. J. Cell Biol. 109:637-652), poleward flux in vitro appears to occur independently of kinetochores or kinetochore microtubules, and therefore may be a general property of relatively stable microtubules within the spindle. We find that microtubules moving towards poles are dynamic structures, and we have estimated the average half-life of fluxing microtubules in vitro to be between approximately 75 and 100 s. We discuss these results with regard to the function of poleward flux in spindle movements in anaphase and prometaphase.

scholarly journals Specific association of an M-phase kinase with isolated mitotic spindles and identification of two of its substrates as MAP4 and MAP1B.

1991 ◽  
Vol 2 (11) ◽  
pp. 861-874 ◽  
Author(s):  
R M Tombes ◽  
J G Peloquin ◽  
G G Borisy
Keyword(s):  
Mitotic Cycle ◽  
Chinese Hamster ◽  
Mitotic Spindles ◽  
Microtubule Associated Proteins ◽  
M Phase ◽  
Associated Proteins ◽  
Specific Association ◽  
Cycle Dependent

Isolated mammalian (Chinese hamster ovary [CHO]) metaphase spindles were found to be enriched in a histone H1 kinase whose activity was mitotic-cycle dependent. Two substrates for the kinase were identified as MAP1B and MAP4. Partially purified spindle kinase retained activity for the spindle microtubule-associated proteins (MAPs) as well as brain and other tissue culture MAPs; on phosphorylation, spindle MAPs exhibited increased immunoreactivity with MPM-2, a monoclonal antibody specific for a subset of mitotic phosphoproteins. Immunofluorescence using an anti-thiophosphoprotein antibody localized in vitro phosphorylated spindle proteins to microtubule fibers, centrosomes, kinetochores, and midbodies. The fractionated spindle kinase was reactive with anti-human p34cdc2 antibodies and with an anti-human cyclin B but not an anti-human cyclin A antibody. We conclude that spindle MAPs undergo mitotic cycle-dependent phosphorylations in vivo and associate with a kinase that remains active on spindle isolation and may be related to p34cdc2.

scholarly journals DSK1, a novel kinesin-related protein from the diatom Cylindrotheca fusiformis that is involved in anaphase spindle elongation.

1996 ◽  
Vol 133 (3) ◽  
pp. 595-604 ◽  
Author(s):  
H Wein ◽  
M Foss ◽  
B Brady ◽  
W Z Cande
Keyword(s):  
Mitotic Spindle ◽  
Related Protein ◽  
Cylindrotheca Fusiformis ◽  
Peptide Antibody ◽  
Spindle Midzone ◽  
Conserved Region ◽  
Spindle Elongation ◽  
Kinesin Superfamily ◽  
Related Proteins

We have identified an 80-kD protein that is involved in mitotic spindle elongation in the diatom Cylindrotheca fusiformis. DSK1 (Diatom Spindle Kinesin 1) was isolated using a peptide antibody raised against a conserved region in the motor domain of the kinesin superfamily. By sequence homology, DSK1 belongs to the central motor family of kinesin-related proteins. Immunoblots using an antibody raised against a non-conserved region of DSK1 show that DSK1 is greatly enriched in mitotic spindle preparations. Anti-DSK1 stains in diatom central spindle with a bias toward the midzone, and staining is retained in the spindle midzone during spindle elongation in vitro. Furthermore, preincubation with anti-DSK1 blocks function in an in vitro spindle elongation assay. This inhibition of spindle elongation can be rescued by preincubating concurrently with the fusion protein against which anti-DSK1 was raised. We conclude that DSK1 is involved in spindle elongation and is likely to be responsible for pushing hal-spindles apart in the spindle midzone.

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