Limits...
Nup358 integrates nuclear envelope breakdown with kinetochore assembly.

Salina D, Enarson P, Rattner JB, Burke B - J. Cell Biol. (2003)

Bottom Line: After NEBD, engagement of spindle microtubules with chromosome-associated kinetochores leads to chromatid segregation.The implication is that Nup358 plays an essential role in integrating NEBD with kinetochore maturation and function.Mitotic arrest associated with Nup358 depletion further suggests that mitotic checkpoint complexes may remain active at nonkinetochore sites.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Cell Biology, University of Florida, Gainesville, FL 32610-0235, USA.

ABSTRACT
Nuclear envelope breakdown (NEBD) and release of condensed chromosomes into the cytoplasm are key events in the early stages of mitosis in metazoans. NEBD involves the disassembly of all major structural elements of the nuclear envelope, including nuclear pore complexes (NPCs), and the dispersal of nuclear membrane components. The breakdown process is facilitated by microtubules of the mitotic spindle. After NEBD, engagement of spindle microtubules with chromosome-associated kinetochores leads to chromatid segregation. Several NPC subunits relocate to kinetochores after NEBD. siRNA-mediated depletion of one of these proteins, Nup358, reveals that it is essential for kinetochore function. In the absence of Nup358, chromosome congression and segregation are severely perturbed. At the same time, the assembly of other kinetochore components is strongly inhibited, leading to aberrant kinetochore structure. The implication is that Nup358 plays an essential role in integrating NEBD with kinetochore maturation and function. Mitotic arrest associated with Nup358 depletion further suggests that mitotic checkpoint complexes may remain active at nonkinetochore sites.

Show MeSH

Related in: MedlinePlus

Mitotic defects associated with Nup358 siRNA treatment of HeLa cells. Nup358 siRNA treatment of HeLa cells leads to the appearance of cells containing multiple micronuclei over a period of 24–96 h (A) as well as the accumulation of cells arrested in prometaphase (B). The latter reach a peak at 120 h, at which time they account for almost 50% of the total mitotic population (B). A gradual increase in apoptosis, peaking at 120 h, is also observed (C). This increase in apoptosis may account for the decline in the number of multinucleate cells observed after 96 h of Nup358 siRNA treatment. In each graph, siRNA-treated populations are represented by light gray bars. Dark gray bars represent control populations.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2172838&req=5

fig1: Mitotic defects associated with Nup358 siRNA treatment of HeLa cells. Nup358 siRNA treatment of HeLa cells leads to the appearance of cells containing multiple micronuclei over a period of 24–96 h (A) as well as the accumulation of cells arrested in prometaphase (B). The latter reach a peak at 120 h, at which time they account for almost 50% of the total mitotic population (B). A gradual increase in apoptosis, peaking at 120 h, is also observed (C). This increase in apoptosis may account for the decline in the number of multinucleate cells observed after 96 h of Nup358 siRNA treatment. In each graph, siRNA-treated populations are represented by light gray bars. Dark gray bars represent control populations.

Mentions: Examination of HeLa cell cultures exposed to Nup358 siRNA reveals a series of striking changes that occur over a period of several days. During the first 24–48 h of siRNA treatment, an accumulation of prometaphase cells becomes apparent (Fig. 1 B). By 120 h, this reaches a peak of almost 50% of the total mitotic population, a threefold increase in the frequency of prometaphase cells over that observed in mock-treated cultures (Fig. 1 B). A second population of cells, characterized by the presence of multiple micronuclei (Fig. 1 A), emerges between 24 and 96 h. This very unusual morphology is rarely encountered in control cultures and is a characteristic feature of Nup358 siRNA treatment. It is not observed after depletion of other nucleoporins such as Nup153 (unpublished data) or when ineffective RNA oligonucleotides are used. As there is a progressive increase in apoptosis leading to a decline in the number of cells containing micronuclei after ∼120 h of Nup358 siRNA treatment (Fig. 1 C), the majority of our subsequent experiments were performed on cells exposed to Nup358 siRNA for a maximum of 96 h.


Nup358 integrates nuclear envelope breakdown with kinetochore assembly.

Salina D, Enarson P, Rattner JB, Burke B - J. Cell Biol. (2003)

Mitotic defects associated with Nup358 siRNA treatment of HeLa cells. Nup358 siRNA treatment of HeLa cells leads to the appearance of cells containing multiple micronuclei over a period of 24–96 h (A) as well as the accumulation of cells arrested in prometaphase (B). The latter reach a peak at 120 h, at which time they account for almost 50% of the total mitotic population (B). A gradual increase in apoptosis, peaking at 120 h, is also observed (C). This increase in apoptosis may account for the decline in the number of multinucleate cells observed after 96 h of Nup358 siRNA treatment. In each graph, siRNA-treated populations are represented by light gray bars. Dark gray bars represent control populations.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2172838&req=5

fig1: Mitotic defects associated with Nup358 siRNA treatment of HeLa cells. Nup358 siRNA treatment of HeLa cells leads to the appearance of cells containing multiple micronuclei over a period of 24–96 h (A) as well as the accumulation of cells arrested in prometaphase (B). The latter reach a peak at 120 h, at which time they account for almost 50% of the total mitotic population (B). A gradual increase in apoptosis, peaking at 120 h, is also observed (C). This increase in apoptosis may account for the decline in the number of multinucleate cells observed after 96 h of Nup358 siRNA treatment. In each graph, siRNA-treated populations are represented by light gray bars. Dark gray bars represent control populations.
Mentions: Examination of HeLa cell cultures exposed to Nup358 siRNA reveals a series of striking changes that occur over a period of several days. During the first 24–48 h of siRNA treatment, an accumulation of prometaphase cells becomes apparent (Fig. 1 B). By 120 h, this reaches a peak of almost 50% of the total mitotic population, a threefold increase in the frequency of prometaphase cells over that observed in mock-treated cultures (Fig. 1 B). A second population of cells, characterized by the presence of multiple micronuclei (Fig. 1 A), emerges between 24 and 96 h. This very unusual morphology is rarely encountered in control cultures and is a characteristic feature of Nup358 siRNA treatment. It is not observed after depletion of other nucleoporins such as Nup153 (unpublished data) or when ineffective RNA oligonucleotides are used. As there is a progressive increase in apoptosis leading to a decline in the number of cells containing micronuclei after ∼120 h of Nup358 siRNA treatment (Fig. 1 C), the majority of our subsequent experiments were performed on cells exposed to Nup358 siRNA for a maximum of 96 h.

Bottom Line: After NEBD, engagement of spindle microtubules with chromosome-associated kinetochores leads to chromatid segregation.The implication is that Nup358 plays an essential role in integrating NEBD with kinetochore maturation and function.Mitotic arrest associated with Nup358 depletion further suggests that mitotic checkpoint complexes may remain active at nonkinetochore sites.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Cell Biology, University of Florida, Gainesville, FL 32610-0235, USA.

ABSTRACT
Nuclear envelope breakdown (NEBD) and release of condensed chromosomes into the cytoplasm are key events in the early stages of mitosis in metazoans. NEBD involves the disassembly of all major structural elements of the nuclear envelope, including nuclear pore complexes (NPCs), and the dispersal of nuclear membrane components. The breakdown process is facilitated by microtubules of the mitotic spindle. After NEBD, engagement of spindle microtubules with chromosome-associated kinetochores leads to chromatid segregation. Several NPC subunits relocate to kinetochores after NEBD. siRNA-mediated depletion of one of these proteins, Nup358, reveals that it is essential for kinetochore function. In the absence of Nup358, chromosome congression and segregation are severely perturbed. At the same time, the assembly of other kinetochore components is strongly inhibited, leading to aberrant kinetochore structure. The implication is that Nup358 plays an essential role in integrating NEBD with kinetochore maturation and function. Mitotic arrest associated with Nup358 depletion further suggests that mitotic checkpoint complexes may remain active at nonkinetochore sites.

Show MeSH
Related in: MedlinePlus