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Updated: Aug 7, 2026

Experimental Approaches to Study Mitochondrial Localization and Function of a Nuclear Cell Cycle Kinase, Cdk1
Published on: February 25, 2016
Phosphorylation by CDK1 regulates XMAP215 function in vitro
R J Vasquez1, D L Gard, L Cassimeris
1Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania 18015, USA.
XMAP215 protein enhances microtubule dynamics, particularly plus-end elongation. Phosphorylation by CDK1 reduces this elongation-promoting effect, suggesting cell cycle regulation of microtubule assembly.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- XMAP215 is a microtubule-associated protein from Xenopus eggs.
- It influences microtubule assembly dynamics, primarily at plus ends.
- XMAP215 phosphorylation during M phase suggests cell cycle-dependent regulation.
Purpose of the Study:
- To investigate the effect of CDK1-mediated phosphorylation on XMAP215 activity.
- To determine how XMAP215 phosphorylation impacts microtubule assembly and disassembly rates.
Main Methods:
- Video-enhanced differential interference contrast (DIC) microscopy.
- Analysis of purified porcine tubulin assembly dynamics.
- Assessment of XMAP215 binding to taxol-stabilized microtubules.
Main Results:
- Unphosphorylated XMAP215 significantly increased microtubule plus-end elongation rates (4.1-fold).
- Phosphorylated XMAP215 showed a reduced increase in elongation (2.4-fold).
- Phosphorylation did not affect the increased shortening rate or XMAP215 binding.
Conclusions:
- CDK1 phosphorylation modulates XMAP215's ability to promote microtubule elongation.
- Microtubules assembled in the presence of XMAP215 exhibit faster subsequent shortening.
- XMAP215 may alter microtubule lattice structure, influencing disassembly dynamics.
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12:26Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay
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