Ase1 domains dynamically slow anaphase spindle elongation and recruit Bim1 to the midzone

Thomas, Ezekiel C; Ismael, Amber; Moore, Jeffrey K.

doi:10.1091/mbc.e20-07-0493-t

Cited by 13 publications

(14 citation statements)

References 65 publications

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“…It is possible that mal3 Δ cells have longer midzones, or a broader distribution of overlap lengths between microtubules. Alternatively, given that Ase1 binds to Bim1 (Mal3) in budding yeast ( Thomas et al, 2020 ), it is possible that this interaction is important for restricting rescues to a narrower region. Ultimately, none of the conditions perturbed the overall organisation of rescues.…”

Section: Resultsmentioning

confidence: 99%

Microtubule rescue at midzone edges promotes overlap stability and prevents spindle collapse during anaphase B

Lera-Ramírez

Nédélec

Tran

2022

eLife

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During anaphase B, molecular motors slide interpolar microtubules to elongate the mitotic spindle, contributing to the separation of chromosomes. However, sliding of antiparallel microtubules reduces their overlap, which may lead to spindle breakage, unless microtubules grow to compensate sliding. How sliding and growth are coordinated is still poorly understood. In this study, we have used the fission yeast S. pombe to measure microtubule dynamics during anaphase B. We report that the coordination of microtubule growth and sliding relies on promoting rescues at the midzone edges. This makes microtubules stable from pole to midzone, while their distal parts including the plus ends alternate between assembly and disassembly. Consequently, the midzone keeps a constant length throughout anaphase, enabling sustained sliding without the need for a precise regulation of microtubule growth speed. Additionally, we found that in S. pombe, which undergoes closed mitosis, microtubule growth speed decreases when the nuclear membrane wraps around the spindle midzone.

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Section: Resultsmentioning

confidence: 99%

Microtubule rescue at midzone edges promotes overlap stability and prevents spindle collapse during anaphase B

Lera-Ramírez

Nédélec

Tran

2022

eLife

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“…Z-series images were processed in FIJI (Wayne Rasband, NIH) using the "Despeckle" plugin followed by the "Remove Outlier" plugin with the radius set to 1 pixel and the threshold 25 to remove bright, outlier pixels. Spindle length over time was determined using a custom analysis program (Thomas, Ismael, and Moore 2020). This program determines the X,Y,Z coordinates of the brightest pixel within the three-dimensional image stack (i.e., the first SPB), applying a Gaussian blur around this pixel, then identifying the second brightest pixel in the image stack (the second SPB).…”

Section: Pre-anaphase Spindle Measurementsmentioning

confidence: 99%

“…We tracked Spc110-mNeonGreen marked SPBs in asynchronous, living cells over five minutes and identified pre-anaphase spindles as those that did not exhibit sustained lengths beyond 2.2 µm during our imaging period. We then measured pole-to-pole distance in 3 dimensions (X,Y,Z) to determine the average spindle length and length variation over time within the spindle of each cell (Thomas et al, 2020;Figure 1E-G). Diploid cells with only one copy of TUB1 exhibit shorter pre-anaphase spindles compared to wild-type controls (Figure 1F, p <0.0001).…”

Section: Distinct Requirements For α-And β-Tubulin Gene Copy Number I...mentioning

confidence: 99%

Asymmetric requirement for α-tubulin over β-tubulin

Wethekam

Moore

2022

Preprint

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How cells regulate the supply of α- and β-tubulin monomers to meet the demand for αβ-heterodimers while avoiding consequences of monomer imbalance is not understood. We investigate the role of gene copy number in tubulin regulation and how shifting the expression of α- or β-tubulin genes impacts tubulin proteostasis and microtubule function. We find that α-tubulin gene copy number is important for maintaining an excess α-tubulin protein compared to β-tubulin protein and preventing accumulation of super-stoichiometric β-tubulin. Super-stoichiometric β-tubulin is toxic to cells, leading to loss of microtubules, formation of non-microtubule assemblies of tubulin, and disrupted cell proliferation. In contrast, decreased β-tubulin or increased α-tubulin has minor effects. We provide evidence that cells rapidly equilibrate the concentration of α-tubulin protein during shifts in α-tubulin isotype expression to maintain a ratio in excess of β-tubulin. We propose an asymmetric relationship between α- and β-tubulins, where α-tubulins are maintained in excess to supply αβ-heterodimers and limit the accumulation of β-tubulin monomers.

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“…Namely, Ase1 supports bipolar spindle formation in S. pombe through its stabilization of microtubule bundles, and even allows the formation of a bipolar spindle in the absence of kinesin-5 mediated antiparallel microtubule sliding 24 . Intriguingly, Ase1 has also been shown, through the same underlying mechanism of antiparallel microtubule stabilization, to slow motor-driven anaphase spindle elongation in budding yeast 7,25 . Thus, we sought to investigate the role of Ase1 in the highly crosslinked nature of S. pombe spindles.…”

Section: Ase1 Crosslinking Prevents Microtubule Depolymerization In S...mentioning

confidence: 99%

Mechanical coupling with the nuclear envelope shapes theS. pombemitotic spindle

Begley

Medina

Zareiesfandabadi

et al. 2022

Preprint

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The fission yeast S. pombe divides via closed mitosis. In short, mitotic spindle elongation and chromosome segregation transpire entirely within the complete nuclear envelope. Both the spindle and nuclear envelope must undergo significant conformation changes and are subject to varying external forces during this process. While the mechanical relationship between the two mitotic structures has been explored previously, much is still left to be discovered. Here, we investigate this relationship by observing the behaviors of spindles and nuclei in live mitotic fission yeasts following laser ablation. First, we characterize these dynamics in molecularly typical S. pombe spindles, finding them to be stabilized by dense crosslinking, before demonstrating that the compressive force acting on the spindle poles is higher in mitotic cells with greater nuclear envelope tension and that spindle compression can be relieved by lessening nuclear envelope tension. We finally examine the differences between the mitotic apparatus in S. pombe and S. japonicus, an evolutionary relative of S. pombe that undergoes semi-open mitosis, and show that S. japonicus mitotic spindles appear to both splay and bend more easily than those of their S. pombe relatives. Altogether, these data suggest that fission yeast spindle crosslinking may be tuned to support spindle extension and oppose nuclear envelope tension.

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Ase1 domains dynamically slow anaphase spindle elongation and recruit Bim1 to the midzone

Cited by 13 publications

References 65 publications

Microtubule rescue at midzone edges promotes overlap stability and prevents spindle collapse during anaphase B

Microtubule rescue at midzone edges promotes overlap stability and prevents spindle collapse during anaphase B

Asymmetric requirement for α-tubulin over β-tubulin

Mechanical coupling with the nuclear envelope shapes theS. pombemitotic spindle

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