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An anillin homologue, Mid2p, acts during fission yeast cytokinesis to organize the septin ring and promote cell separation.

Tasto JJ, Morrell JL, Gould KL - J. Cell Biol. (2003)

Bottom Line: Simanis. 1996.Mid2p colocalizes with septins, and mid2 Delta cells display disorganized, diffuse septin rings and a cell separation defect similar to septin deletion strains. mid2 gene expression and protein levels fluctuate during the cell cycle in a sep1- and Skp1/Cdc53/F-box (SCF)-dependent manner, respectively, implying that Mid2p activity must be carefully regulated.Overproduction of Mid2p depolarizes cell growth and affects the organization of both the septin and actin cytoskeletons.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.

ABSTRACT
Anillin is a conserved protein required for cell division (Field, C.M., and B.M. Alberts. 1995. J. Cell Biol. 131:165-178; Oegema, K., M.S. Savoian, T.J. Mitchison, and C.M. Field. 2000. J. Cell Biol. 150:539-552). One fission yeast homologue of anillin, Mid1p, is necessary for the proper placement of the division site within the cell (Chang, F., A. Woollard, and P. Nurse. 1996. J. Cell Sci. 109(Pt 1):131-142; Sohrmann, M., C. Fankhauser, C. Brodbeck, and V. Simanis. 1996. Genes Dev. 10:2707-2719). Here, we identify and characterize a second fission yeast anillin homologue, Mid2p, which is not orthologous with Mid1p. Mid2p localizes as a single ring in the middle of the cell after anaphase in a septin- and actin-dependent manner and splits into two rings during septation. Mid2p colocalizes with septins, and mid2 Delta cells display disorganized, diffuse septin rings and a cell separation defect similar to septin deletion strains. mid2 gene expression and protein levels fluctuate during the cell cycle in a sep1- and Skp1/Cdc53/F-box (SCF)-dependent manner, respectively, implying that Mid2p activity must be carefully regulated. Overproduction of Mid2p depolarizes cell growth and affects the organization of both the septin and actin cytoskeletons. In the presence of a nondegradable Mid2p fragment, the septin ring is stabilized and cell cycle progression is delayed. These results suggest that Mid2p influences septin ring organization at the site of cell division and its turnover might normally be required to permit septin ring disassembly.

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Mid2p localization requires F-actin and septins. (A) cdc25-22 mid2–GFP cells (KGY3123) were grown to mid-log phase at 25°C, shifted to 36°C for 4 h, and released to 25°C in either DMSO or 100 μM LatA. Images of live cells at the indicated times are presented. (B) Asynchronously growing mid2–GFP cells (KGY2422) were treated with DMSO or 200 μM LatA for 15 min and fixed with formaldehyde. The actin cytoskeleton was visualized with AlexaFluor®594-phalloidin. (C) Differential interference contrast images of spn4Δ (KGY3986) or mid2Δ spn4Δ (KGY4356) grown in YE medium at 32°C. (D) mid2–GFP spn4Δ cells (KGY4217) were grown at 32°C, fixed with ethanol, and stained with DAPI. Bars, 5 μm.
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fig5: Mid2p localization requires F-actin and septins. (A) cdc25-22 mid2–GFP cells (KGY3123) were grown to mid-log phase at 25°C, shifted to 36°C for 4 h, and released to 25°C in either DMSO or 100 μM LatA. Images of live cells at the indicated times are presented. (B) Asynchronously growing mid2–GFP cells (KGY2422) were treated with DMSO or 200 μM LatA for 15 min and fixed with formaldehyde. The actin cytoskeleton was visualized with AlexaFluor®594-phalloidin. (C) Differential interference contrast images of spn4Δ (KGY3986) or mid2Δ spn4Δ (KGY4356) grown in YE medium at 32°C. (D) mid2–GFP spn4Δ cells (KGY4217) were grown at 32°C, fixed with ethanol, and stained with DAPI. Bars, 5 μm.

Mentions: To determine if Mid2p required F-actin for its association with the medial ring, Mid2p–GFP localization was monitored in cells released from a cdc25-22 block into either DMSO or latrunculin A (LatA), which promotes F-actin depolymerization (Ayscough et al., 1997). In control cells, the first Mid2p–GFP rings appeared at 60 min and persisted (Fig. 5 A; unpublished data). In contrast, the LatA-treated cells failed to form Mid2p–GFP rings even after 150 min (Fig. 5 A). In an asynchronous culture of cells, however, Mid2p–GFP persisted at the medial ring 15 min after LatA addition (Fig. 5 B), suggesting that once recruited, Mid2p's association with the medial ring is actin independent.


An anillin homologue, Mid2p, acts during fission yeast cytokinesis to organize the septin ring and promote cell separation.

Tasto JJ, Morrell JL, Gould KL - J. Cell Biol. (2003)

Mid2p localization requires F-actin and septins. (A) cdc25-22 mid2–GFP cells (KGY3123) were grown to mid-log phase at 25°C, shifted to 36°C for 4 h, and released to 25°C in either DMSO or 100 μM LatA. Images of live cells at the indicated times are presented. (B) Asynchronously growing mid2–GFP cells (KGY2422) were treated with DMSO or 200 μM LatA for 15 min and fixed with formaldehyde. The actin cytoskeleton was visualized with AlexaFluor®594-phalloidin. (C) Differential interference contrast images of spn4Δ (KGY3986) or mid2Δ spn4Δ (KGY4356) grown in YE medium at 32°C. (D) mid2–GFP spn4Δ cells (KGY4217) were grown at 32°C, fixed with ethanol, and stained with DAPI. Bars, 5 μm.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2172762&req=5

fig5: Mid2p localization requires F-actin and septins. (A) cdc25-22 mid2–GFP cells (KGY3123) were grown to mid-log phase at 25°C, shifted to 36°C for 4 h, and released to 25°C in either DMSO or 100 μM LatA. Images of live cells at the indicated times are presented. (B) Asynchronously growing mid2–GFP cells (KGY2422) were treated with DMSO or 200 μM LatA for 15 min and fixed with formaldehyde. The actin cytoskeleton was visualized with AlexaFluor®594-phalloidin. (C) Differential interference contrast images of spn4Δ (KGY3986) or mid2Δ spn4Δ (KGY4356) grown in YE medium at 32°C. (D) mid2–GFP spn4Δ cells (KGY4217) were grown at 32°C, fixed with ethanol, and stained with DAPI. Bars, 5 μm.
Mentions: To determine if Mid2p required F-actin for its association with the medial ring, Mid2p–GFP localization was monitored in cells released from a cdc25-22 block into either DMSO or latrunculin A (LatA), which promotes F-actin depolymerization (Ayscough et al., 1997). In control cells, the first Mid2p–GFP rings appeared at 60 min and persisted (Fig. 5 A; unpublished data). In contrast, the LatA-treated cells failed to form Mid2p–GFP rings even after 150 min (Fig. 5 A). In an asynchronous culture of cells, however, Mid2p–GFP persisted at the medial ring 15 min after LatA addition (Fig. 5 B), suggesting that once recruited, Mid2p's association with the medial ring is actin independent.

Bottom Line: Simanis. 1996.Mid2p colocalizes with septins, and mid2 Delta cells display disorganized, diffuse septin rings and a cell separation defect similar to septin deletion strains. mid2 gene expression and protein levels fluctuate during the cell cycle in a sep1- and Skp1/Cdc53/F-box (SCF)-dependent manner, respectively, implying that Mid2p activity must be carefully regulated.Overproduction of Mid2p depolarizes cell growth and affects the organization of both the septin and actin cytoskeletons.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.

ABSTRACT
Anillin is a conserved protein required for cell division (Field, C.M., and B.M. Alberts. 1995. J. Cell Biol. 131:165-178; Oegema, K., M.S. Savoian, T.J. Mitchison, and C.M. Field. 2000. J. Cell Biol. 150:539-552). One fission yeast homologue of anillin, Mid1p, is necessary for the proper placement of the division site within the cell (Chang, F., A. Woollard, and P. Nurse. 1996. J. Cell Sci. 109(Pt 1):131-142; Sohrmann, M., C. Fankhauser, C. Brodbeck, and V. Simanis. 1996. Genes Dev. 10:2707-2719). Here, we identify and characterize a second fission yeast anillin homologue, Mid2p, which is not orthologous with Mid1p. Mid2p localizes as a single ring in the middle of the cell after anaphase in a septin- and actin-dependent manner and splits into two rings during septation. Mid2p colocalizes with septins, and mid2 Delta cells display disorganized, diffuse septin rings and a cell separation defect similar to septin deletion strains. mid2 gene expression and protein levels fluctuate during the cell cycle in a sep1- and Skp1/Cdc53/F-box (SCF)-dependent manner, respectively, implying that Mid2p activity must be carefully regulated. Overproduction of Mid2p depolarizes cell growth and affects the organization of both the septin and actin cytoskeletons. In the presence of a nondegradable Mid2p fragment, the septin ring is stabilized and cell cycle progression is delayed. These results suggest that Mid2p influences septin ring organization at the site of cell division and its turnover might normally be required to permit septin ring disassembly.

Show MeSH
Related in: MedlinePlus