Page last updated: 2024-10-24

mitotic spindle disassembly

Definition

Target type: biologicalprocess

The controlled breakdown of the spindle during a mitotic cell cycle. [GOC:ai]

Mitotic spindle disassembly is a critical and highly regulated process that marks the end of mitosis and allows the cell to proceed to cytokinesis. It involves the controlled breakdown of the microtubule-based structure responsible for segregating chromosomes during cell division. Here's a detailed breakdown of the process:

**1. Dephosphorylation of Key Proteins:**
- During anaphase, the mitotic cyclin-dependent kinase (CDK) activity declines, leading to the dephosphorylation of key spindle proteins.
- One crucial target is the protein **Aurora B kinase**, a major regulator of spindle assembly and stability. Dephosphorylation of Aurora B leads to its inactivation.
- Other proteins that undergo dephosphorylation include **katanin**, a microtubule-severing enzyme, and **MCAK** (mitotic centromere-associated kinesin), a microtubule depolymerase.

**2. Microtubule Severing and Depolymerization:**
- **Katanin** plays a central role in severing microtubules, effectively breaking them apart. This process is crucial for dismantling the spindle poles and disrupting the microtubule network.
- **MCAK** and other microtubule depolymerases, such as **stathmin**, act to shorten microtubules by removing tubulin subunits from their ends. This depolymerization weakens the spindle and facilitates its disassembly.

**3. Dissociation of Sister Chromatids:**
- Once the spindle fibers are severed and depolymerized, the sister chromatids, which were held together by the spindle, are freed from each other.
- This process, called **chromosome decondensation**, allows the chromosomes to relax and become less condensed.

**4. Spindle Pole Disassembly:**
- The spindle poles, which are the anchoring points of the spindle fibers, also undergo disassembly.
- **Cytoplasmic dynein**, a motor protein, plays a significant role in pulling the spindle poles apart.
- The spindle poles are then disassembled into their individual components, including centrosomes and associated proteins.

**5. Cytokinesis and Cell Division:**
- With the spindle fully disassembled, the cell can now proceed to cytokinesis, the division of the cytoplasm.
- This process is driven by the formation of a contractile ring made of actin and myosin filaments, which pinches the cell membrane inward.
- Ultimately, cytokinesis results in the formation of two daughter cells, each with its own complete set of chromosomes.'
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Proteins (1)

ProteinDefinitionTaxonomy
Transitional endoplasmic reticulum ATPaseA transitional endoplasmic reticulum ATPase that is encoded in the genome of human. [PRO:DNx, UniProtKB:P55072]Homo sapiens (human)

Compounds (6)

CompoundDefinitionClassesRoles
clotrimazoleconazole antifungal drug;
imidazole antifungal drug;
imidazoles;
monochlorobenzenes
antiinfective agent;
environmental contaminant;
xenobiotic
Methylenedioxycinnamic acidhydroxycinnamic acid
3,4-methylenedioxy-beta-nitrostyrene3,4-methylenedioxy-beta-nitrostyrene: tyrosine kinase inhibitor that prevents platelet glycoprotein IIb/IIIa activation; structure in first source
4-(4-(4-chloro-phenyl)thiazol-2-ylamino)phenolsubstituted aniline
ML240ML240 : A member of the class of quinazolines that is quinazoline which is substituted at positions 2, 5 and 8 by 2-amino-1H-benzimidazol-1-yl, benzylnitrilo and methoxy groups, respectively. It is a ATP-competetive inhibitor of AAA ATPase p97, also known as valosin-containing protein (VCP).aromatic amine;
aromatic ether;
benzimidazoles;
primary amino compound;
quinazolines;
secondary amino compound
antineoplastic agent
ganciclovir2-aminopurines;
oxopurine
antiinfective agent;
antiviral drug