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Identification of a functional destruction box in the Xenopus laevis aurora-A kinase pEg2
Y Arlot-Bonnemains1, A Klotzbucher, R Giet
1Groupe Cycle Cellulaire, UMR 6061 Génétique et Développement, CNRS-Université de Rennes 1, IFR 97 Génomique Fonctionnelle et Santé, Faculté de Médecine, 2 avenue du Pr Léon Bernard, CS 34317, 35043 Rennes Cedex, France. yannick.arlot@univ-rennes1.fr
Abstract:
Like for all aurora-A kinases, the Xenopus pEg2 kinase level peaks in G(2)/M and is hardly detectable in G(1) cells, suggesting that the protein is degraded upon exit from mitosis as reported for the human aurora-A kinase. We identified for the first time a sequence RxxL in the C-terminal end of the kinase catalytic domain. Mutation of this sequence RxxL to RxxI suppresses the ubiquitination of the protein as well as its degradation. The sequence RxxL corresponding to the pEg2 functional destruction box has been conserved throughout evolution in all aurora kinases including aurora-A, -B and -C.
Insights
Xenopus pEg2 kinase degradation is regulated by a conserved RxxL destruction box. Mutating this sequence prevents ubiquitination and degradation, revealing a key mechanism in cell cycle control.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Aurora kinases, including aurora-A, play critical roles in cell cycle regulation.
- Xenopus pEg2 kinase levels peak during G(2)/M phase and decrease in G(1).
- Protein degradation is essential for proper cell cycle progression, particularly after mitosis.
Purpose of the Study:
- To investigate the mechanism regulating Xenopus pEg2 kinase degradation.
- To identify specific protein sequences involved in pEg2 ubiquitination and degradation.
- To determine the evolutionary conservation of these regulatory sequences in aurora kinases.
Main Methods:
- Identification of conserved sequences within the Xenopus pEg2 kinase catalytic domain.
- Site-directed mutagenesis of the identified RxxL sequence to RxxI.
- Assessment of protein ubiquitination levels using Western blotting.
- Analysis of protein degradation rates in cell cycle-arrested cells.
Main Results:
- A novel RxxL sequence was identified at the C-terminal end of the Xenopus pEg2 kinase catalytic domain.
- Mutation of the RxxL sequence to RxxI abolished pEg2 ubiquitination.
- The RxxL to RxxI mutation prevented the degradation of pEg2 protein.
- The RxxL destruction box motif is conserved across aurora-A, -B, and -C kinases in various species.
Conclusions:
- The RxxL sequence functions as a destruction box, targeting Xenopus pEg2 kinase for ubiquitination and degradation.
- This degradation mechanism is crucial for regulating pEg2 levels during the cell cycle.
- The conserved nature of the RxxL motif suggests a fundamental role in aurora kinase regulation across evolution.