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)

Compounds (6)