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Updated: May 9, 2026

Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay
Published on: May 3, 2018
NuMA phosphorylation by CDK1 couples mitotic progression with cortical dynein function
Sachin Kotak1, Coralie Busso, Pierre Gönczy
1Swiss Institute for Experimental Cancer Research (ISREC), School of Life Sciences, Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland.
Nuclear mitotic apparatus protein (NuMA) phosphorylation controls spindle positioning and elongation during cell division. This phosphorylation balance ensures correct spindle function by regulating cortical dynein levels.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- Proper cell division relies on accurate spindle positioning and elongation.
- The NuMA/LGN/Gαi complex anchors dynein at the cell cortex for spindle positioning in metaphase.
- Mechanisms linking mitotic progression to spindle behavior are not fully understood.
Purpose of the Study:
- Investigate the role of the NuMA complex in anaphase spindle elongation.
- Elucidate the mechanisms coordinating mitotic progression with spindle function.
- Determine how NuMA phosphorylation influences spindle positioning and elongation.
Main Methods:
- Western blotting to assess protein levels.
- Immunofluorescence microscopy to visualize protein localization.
- Phosphatase and kinase activity assays.
Main Results:
- Cortical dynein levels increase during anaphase, dependent on NuMA.
- CDK1 phosphorylation of NuMA at T2055 inhibits its cortical localization during metaphase.
- PPP2CA phosphatase activity counteracts CDK1 phosphorylation, regulating metaphase spindle positioning.
- NuMA dephosphorylation upon CDK1 inactivation in anaphase promotes cortical dynein enrichment and spindle elongation.
Conclusions:
- NuMA phosphorylation status is a key regulator of spindle positioning and elongation.
- A phosphorylation-dephosphorylation switch in NuMA coordinates mitotic progression with spindle dynamics.
- This mechanism ensures robust spindle function throughout cell division.
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