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Subgroup II PAK-mediated phosphorylation regulates Ran activity during mitosis
Guillaume Bompard1, Gabriel Rabeharivelo, Marie Frank
1Universités Montpellier 2 et 1, IFR122, 34293 Montpellier, France.
The Journal of Cell Biology
|September 1, 2010
Summary
p21-activated kinase 4 (PAK4) phosphorylates the essential GTPase Ran during mitosis. This phosphorylation regulates Ran
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Ran GTPase is crucial for nuclear transport, mitosis, and nuclear envelope formation.
- Ran's functions are regulated by its interaction partners and a Ran-GTP gradient from chromatin.
Purpose of the Study:
- To identify novel regulatory mechanisms for Ran.
- To investigate the role of p21-activated kinase 4 (PAK4) in Ran regulation.
Main Methods:
- Investigated Ran phosphorylation by PAK4 using biochemical assays.
- Analyzed the association of phosphorylated Ran and PAK4 with mitotic spindle components.
- Utilized Xenopus egg extracts to study the effects of Ran mutants on microtubule aster formation.
- Assessed the impact of Ran phosphorylation on binding to RCC1 and RanGAP1.
Main Results:
- Ran is a substrate for PAK4, with serine-135 phosphorylation increasing during mitosis.
- Phosphorylated Ran and active PAK4 associate with the mitotic spindle.
- A GDP-bound Ran phosphomimetic mutant impaired GDP/GTP exchange and microtubule aster induction.
- Phosphorylation of GTP-bound Ran promoted aster nucleation.
- Ran phosphorylation at serine-135 hindered binding to RCC1 and RanGAP1.
Conclusions:
- PAK4-mediated phosphorylation represents a novel regulatory mechanism for Ran.
- Phosphorylation of Ran by PAK4 influences its interactions with key partners like RCC1 and RanGAP1.
- This regulation is critical for the assembly of Ran-dependent complexes on the mitotic spindle during cell division.
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