scholarly journals Molecular architecture of a kinetochore–microtubule attachment site

2006 ◽  
Vol 8 (6) ◽  
pp. 581-585 ◽  
Author(s):  
Ajit P. Joglekar ◽  
David C. Bouck ◽  
Jeffrey N. Molk ◽  
Kerry S. Bloom ◽  
Edward D. Salmon
Keyword(s):  
Attachment Site ◽  
Molecular Architecture ◽  
Microtubule Attachment

scholarly journals Molecular architecture of the kinetochore-microtubule attachment site is conserved between point and regional centromeres

2008 ◽  
Vol 181 (4) ◽  
pp. 587-594 ◽  
Author(s):  
Ajit P. Joglekar ◽  
David Bouck ◽  
Ken Finley ◽  
Xingkun Liu ◽  
Yakun Wan ◽  
...  
Keyword(s):  
Protein Complexes ◽  
Budding Yeast ◽  
Attachment Site ◽  
Molecular Architecture ◽  
Kinetochore Protein ◽  
Kinetochore Assembly ◽  
Microtubule Attachment ◽  
Unique Site ◽  
Structural Subunit ◽  
Quantitative Fluorescence

Point and regional centromeres specify a unique site on each chromosome for kinetochore assembly. The point centromere in budding yeast is a unique 150-bp DNA sequence, which supports a kinetochore with only one microtubule attachment. In contrast, regional centromeres are complex in architecture, can be up to 5 Mb in length, and typically support many kinetochore-microtubule attachments. We used quantitative fluorescence microscopy to count the number of core structural kinetochore protein complexes at the regional centromeres in fission yeast and Candida albicans. We find that the number of CENP-A nucleosomes at these centromeres reflects the number of kinetochore-microtubule attachments instead of their length. The numbers of kinetochore protein complexes per microtubule attachment are nearly identical to the numbers in a budding yeast kinetochore. These findings reveal that kinetochores with multiple microtubule attachments are mainly built by repeating a conserved structural subunit that is equivalent to a single microtubule attachment site.

scholarly journals The molecular architecture of the meiotic spindle is remodeled during metaphase arrest in oocytes

2019 ◽  
Vol 218 (9) ◽  
pp. 2854-2864 ◽  
Author(s):  
Mariana F.A. Costa ◽  
Hiroyuki Ohkura
Keyword(s):  
Drosophila Melanogaster ◽  
Meiotic Spindle ◽  
Cross Linking ◽  
Molecular Architecture ◽  
Metaphase Arrest ◽  
Bipolar Spindle ◽  
Microtubule Attachment ◽  
Insight Into ◽  
Transgenic Flies ◽  
Metaphase I

Before fertilization, oocytes of most species undergo a long, natural arrest in metaphase. Before this, prometaphase I is also prolonged, due to late stable kinetochore–microtubule attachment. How oocytes stably maintain the dynamic spindle for hours during these periods is poorly understood. Here we report that the bipolar spindle changes its molecular architecture during the long prometaphase/metaphase I in Drosophila melanogaster oocytes. By generating transgenic flies expressing GFP-tagged spindle proteins, we found that 14 of 25 spindle proteins change their distribution in the bipolar spindle. Among them, microtubule cross-linking kinesins, MKlp1/Pavarotti and kinesin-5/Klp61F, accumulate to the spindle equator in late metaphase. We found that the late equator accumulation of MKlp1/Pavarotti is regulated by a mechanism distinct from that in mitosis. While MKlp1/Pavarotti contributes to the control of spindle length, kinesin-5/Klp61F is crucial for maintaining a bipolar spindle during metaphase I arrest. Our study provides novel insight into how oocytes maintain a bipolar spindle during metaphase arrest.

scholarly journals Stability of microtubule attachment to metaphase kinetochores in PtK1 cells

1990 ◽  
Vol 96 (1) ◽  
pp. 9-15 ◽  
Author(s):  
L. Cassimeris ◽  
C.L. Rieder ◽  
G. Rupp ◽  
E.D. Salmon
Keyword(s):  
Attachment Site ◽  
Microtubule Assembly ◽  
Microtubule Depolymerization ◽  
Spindle Poles ◽  
Microtubule Attachment ◽  
Section Electron ◽  
The Mean ◽  
Serial Section Electron Microscopy ◽  
The Stability ◽  
Section Electron Microscopy

Kinetochore microtubules are known to be differentially stable to a variety of microtubule depolymerization agents compared to the non-kinetochore polar microtubules, but the dynamics of microtubule attachment to the kinetochore is currently controversial. We have examined the stability of kinetochore microtubules in metaphase PtK1 spindles at 23 degrees C when microtubule assembly is abruptly blocked with the drug nocodazole. Metaphase cells were incubated in medium containing 34 microM nocodazole for various times before fixation and processing either for immunofluorescence light microscopy or serial-section electron microscopy. Microtubules not associated with kinetochore fibers disappeared completely in less than 1 min. Kinetochore fibers persisted and shortened, as the spindle poles moved close to the chromosomes over a 10–20 min interval. During this shortening process, the number of kinetochore microtubules decreased slowly. The mean number of kinetochore microtubules was 24 +/− 5 in control cells and zero in cells incubated with nocodazole for 20 min. The half-time of microtubule attachment to the kinetochore was approximately 7.5 min. These results show that when microtubule assembly is blocked, kinetochore microtubules shorten more slowly and persist about 10 times longer than the labile polar microtubules. If kinetochore microtubules shorten by tubulin dissociation at their plus-ends like the non-kinetochore polar microtubules, then the microtubule surface lattice must be able to translocate through the kinetochore attachment site without frequent detachment occurring.

scholarly journals Individual pericentromeres display coordinated motion and stretching in the yeast spindle

2013 ◽  
Vol 203 (3) ◽  
pp. 407-416 ◽  
Author(s):  
Andrew D. Stephens ◽  
Chloe E. Snider ◽  
Julian Haase ◽  
Rachel A. Haggerty ◽  
Paula A. Vasquez ◽  
...  
Keyword(s):  
Stochastic Dynamics ◽  
Attachment Site ◽  
Coordinated Motion ◽  
Daughter Cells ◽  
Microtubule Attachment ◽  
Sister Chromatids ◽  
Attachment Sites ◽  
Physical Linkage ◽  
Pulling Force ◽  
Structural Maintenance Of Chromosomes

The mitotic segregation apparatus composed of microtubules and chromatin functions to faithfully partition a duplicated genome into two daughter cells. Microtubules exert extensional pulling force on sister chromatids toward opposite poles, whereas pericentric chromatin resists with contractile springlike properties. Tension generated from these opposing forces silences the spindle checkpoint to ensure accurate chromosome segregation. It is unknown how the cell senses tension across multiple microtubule attachment sites, considering the stochastic dynamics of microtubule growth and shortening. In budding yeast, there is one microtubule attachment site per chromosome. By labeling several chromosomes, we find that pericentromeres display coordinated motion and stretching in metaphase. The pericentromeres of different chromosomes exhibit physical linkage dependent on centromere function and structural maintenance of chromosomes complexes. Coordinated motion is dependent on condensin and the kinesin motor Cin8, whereas coordinated stretching is dependent on pericentric cohesin and Cin8. Linking of pericentric chromatin through cohesin, condensin, and kinetochore microtubules functions to coordinate dynamics across multiple attachment sites.

scholarly journals Hec1 and Nuf2 Are Core Components of the Kinetochore Outer Plate Essential for Organizing Microtubule Attachment Sites

2005 ◽  
Vol 16 (2) ◽  
pp. 519-531 ◽  
Author(s):  
Jennifer G. DeLuca ◽  
Yimin Dong ◽  
Polla Hergert ◽  
Joshua Strauss ◽  
Jennifer M. Hickey ◽  
...  
Keyword(s):  
Spindle Checkpoint ◽  
Attachment Site ◽  
Outer Plate ◽  
Microtubule Attachment ◽  
Attachment Sites ◽  
Outer Domain ◽  
Core Components ◽  
Fluorescence Light ◽  
Microtubule Formation ◽  
Stable Core

A major goal in the study of vertebrate mitosis is to identify proteins that create the kinetochore-microtubule attachment site. Attachment sites within the kinetochore outer plate generate microtubule dependent forces for chromosome movement and regulate spindle checkpoint protein assembly at the kinetochore. The Ndc80 complex, comprised of Ndc80 (Hec1), Nuf2, Spc24, and Spc25, is essential for metaphase chromosome alignment and anaphase chromosome segregation. It has also been suggested to have roles in kinetochore microtubule formation, production of kinetochore tension, and the spindle checkpoint. Here we show that Nuf2 and Hec1 localize throughout the outer plate, and not the corona, of the vertebrate kinetochore. They are part of a stable “core” region whose assembly dynamics are distinct from other outer domain spindle checkpoint and motor proteins. Furthermore, Nuf2 and Hec1 are required for formation and/or maintenance of the outer plate structure itself. Fluorescence light microscopy, live cell imaging, and electron microscopy provide quantitative data demonstrating that Nuf2 and Hec1 are essential for normal kinetochore microtubule attachment. Our results indicate that Nuf2 and Hec1 are required for organization of stable microtubule plus-end binding sites in the outer plate that are needed for the sustained poleward forces required for biorientation at kinetochores.

Sign in / Sign up

Export Citation Format

Share Document