Limits...
Dynein is a transient kinetochore component whose binding is regulated by microtubule attachment, not tension.

King JM, Hays TS, Nicklas RB - J. Cell Biol. (2000)

Bottom Line: We have determined that these differences in staining intensity reflect differences in amounts of dynein associated with the kinetochore.As a result, the bulk of the dynein leaves the kinetochore very early in mitosis, soon after the kinetochores begin to attach to microtubules.The possible functions of this dynein fraction are therefore limited to the initial attachment and movement of chromosomes and/or to a role in the mitotic checkpoint.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Duke University, Durham, North Carolina 27708, USA.

ABSTRACT
Cytoplasmic dynein is the only known kinetochore protein capable of driving chromosome movement toward spindle poles. In grasshopper spermatocytes, dynein immunofluorescence staining is bright at prometaphase kinetochores and dimmer at metaphase kinetochores. We have determined that these differences in staining intensity reflect differences in amounts of dynein associated with the kinetochore. Metaphase kinetochores regain bright dynein staining if they are detached from spindle microtubules by micromanipulation and kept detached for 10 min. We show that this increase in dynein staining is not caused by the retraction or unmasking of dynein upon detachment. Thus, dynein genuinely is a transient component of spermatocyte kinetochores. We further show that microtubule attachment, not tension, regulates dynein localization at kinetochores. Dynein binding is extremely sensitive to the presence of microtubules: fewer than half the normal number of kinetochore microtubules leads to the loss of most kinetochoric dynein. As a result, the bulk of the dynein leaves the kinetochore very early in mitosis, soon after the kinetochores begin to attach to microtubules. The possible functions of this dynein fraction are therefore limited to the initial attachment and movement of chromosomes and/or to a role in the mitotic checkpoint.

Show MeSH

Related in: MedlinePlus

Dynein staining in grasshopper spermatocytes. (A and C) Superimposed phase–contrast and immunofluorescence images. (B and D) Immunofluorescence images. The dynein antibody stains the spindle, spindle poles, and kinetochores (arrowheads) in both prometaphase (A and B) and metaphase (C and D) cells (the absence of a tight metaphase plate in C and D is due to cell lysis before fixation). Dynein staining is far brighter on prometaphase kinetochores (A and B) than at metaphase (C and D). *Spindle poles. Bar, 10 μm.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2169441&req=5

Figure 2: Dynein staining in grasshopper spermatocytes. (A and C) Superimposed phase–contrast and immunofluorescence images. (B and D) Immunofluorescence images. The dynein antibody stains the spindle, spindle poles, and kinetochores (arrowheads) in both prometaphase (A and B) and metaphase (C and D) cells (the absence of a tight metaphase plate in C and D is due to cell lysis before fixation). Dynein staining is far brighter on prometaphase kinetochores (A and B) than at metaphase (C and D). *Spindle poles. Bar, 10 μm.

Mentions: In grasshopper spermatocytes, the dynein heavy chain antibody localizes to the spindle, spindle poles, and kinetochores (Fig. 2). The amount of antibody detected at kinetochores depends upon the stage of the spermatocytes: prometaphase kinetochores in meiosis I stain brightly for dynein (Fig. 2A and Fig. B, arrowheads), whereas metaphase kinetochores are more dimly labeled (Fig. 2C and Fig. D, arrowheads).


Dynein is a transient kinetochore component whose binding is regulated by microtubule attachment, not tension.

King JM, Hays TS, Nicklas RB - J. Cell Biol. (2000)

Dynein staining in grasshopper spermatocytes. (A and C) Superimposed phase–contrast and immunofluorescence images. (B and D) Immunofluorescence images. The dynein antibody stains the spindle, spindle poles, and kinetochores (arrowheads) in both prometaphase (A and B) and metaphase (C and D) cells (the absence of a tight metaphase plate in C and D is due to cell lysis before fixation). Dynein staining is far brighter on prometaphase kinetochores (A and B) than at metaphase (C and D). *Spindle poles. Bar, 10 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2169441&req=5

Figure 2: Dynein staining in grasshopper spermatocytes. (A and C) Superimposed phase–contrast and immunofluorescence images. (B and D) Immunofluorescence images. The dynein antibody stains the spindle, spindle poles, and kinetochores (arrowheads) in both prometaphase (A and B) and metaphase (C and D) cells (the absence of a tight metaphase plate in C and D is due to cell lysis before fixation). Dynein staining is far brighter on prometaphase kinetochores (A and B) than at metaphase (C and D). *Spindle poles. Bar, 10 μm.
Mentions: In grasshopper spermatocytes, the dynein heavy chain antibody localizes to the spindle, spindle poles, and kinetochores (Fig. 2). The amount of antibody detected at kinetochores depends upon the stage of the spermatocytes: prometaphase kinetochores in meiosis I stain brightly for dynein (Fig. 2A and Fig. B, arrowheads), whereas metaphase kinetochores are more dimly labeled (Fig. 2C and Fig. D, arrowheads).

Bottom Line: We have determined that these differences in staining intensity reflect differences in amounts of dynein associated with the kinetochore.As a result, the bulk of the dynein leaves the kinetochore very early in mitosis, soon after the kinetochores begin to attach to microtubules.The possible functions of this dynein fraction are therefore limited to the initial attachment and movement of chromosomes and/or to a role in the mitotic checkpoint.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Duke University, Durham, North Carolina 27708, USA.

ABSTRACT
Cytoplasmic dynein is the only known kinetochore protein capable of driving chromosome movement toward spindle poles. In grasshopper spermatocytes, dynein immunofluorescence staining is bright at prometaphase kinetochores and dimmer at metaphase kinetochores. We have determined that these differences in staining intensity reflect differences in amounts of dynein associated with the kinetochore. Metaphase kinetochores regain bright dynein staining if they are detached from spindle microtubules by micromanipulation and kept detached for 10 min. We show that this increase in dynein staining is not caused by the retraction or unmasking of dynein upon detachment. Thus, dynein genuinely is a transient component of spermatocyte kinetochores. We further show that microtubule attachment, not tension, regulates dynein localization at kinetochores. Dynein binding is extremely sensitive to the presence of microtubules: fewer than half the normal number of kinetochore microtubules leads to the loss of most kinetochoric dynein. As a result, the bulk of the dynein leaves the kinetochore very early in mitosis, soon after the kinetochores begin to attach to microtubules. The possible functions of this dynein fraction are therefore limited to the initial attachment and movement of chromosomes and/or to a role in the mitotic checkpoint.

Show MeSH
Related in: MedlinePlus