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Use of CDC2 from etoposide-treated cells as substrate to assay CDC25 phosphatase activity
1IPBS-CNRS, Université Paul Sabatier, Toulouse, France.
Abstract:
Cyclin-dependent kinases (CDKs) regulate the key transition of the cell cycle in all organisms. In response to Etoposide (VP-16) induced DNA damage, cells undergo a G2-phase arrest resulting in the accumulation of inactive CDK1 (CDC2) kinase complexes. Here we report that upon Etoposide treatment CDC2 is phosphorylated on tyrosine 15 and is dephosphorylated and activated in vitro by recombinant CDC25 phosphatase. We also show that inactive CDC2 kinase from Etoposide-treated cells can be used as a substrate in a sensitive two-step assay of CDC25 phosphatase. This assay, which is very simple to set-up, is based on the monitoring of CDC2 kinase activity after CDC25-dependent dephosphorylation. It provides the possibility to use a highly physiological substrate in antimitotic drugs screening.
Insights
DNA damage triggers cell cycle arrest by inactivating CDK1 (CDC2) kinase. This study shows CDC25 phosphatase can reactivate CDC2, enabling a new assay for screening antimitotic drugs.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Cyclin-dependent kinases (CDKs) are crucial regulators of the cell cycle.
- DNA damage, induced by agents like Etoposide (VP-16), causes G2-phase arrest.
- This arrest leads to the accumulation of inactive CDK1 (CDC2) kinase complexes.
Purpose of the Study:
- To investigate the mechanism of CDK1 (CDC2) inactivation and reactivation following DNA damage.
- To develop a novel assay for screening antimitotic drugs using a physiological substrate.
Main Methods:
- Treatment of cells with Etoposide (VP-16) to induce DNA damage and cell cycle arrest.
- Analysis of CDK1 (CDC2) phosphorylation status, specifically on tyrosine 15.
- In vitro activation of inactive CDK1 (CDC2) using recombinant CDC25 phosphatase.
- Development of a two-step assay monitoring CDC2 kinase activity post-CDC25 dephosphorylation.
Main Results:
- Etoposide treatment results in tyrosine 15 phosphorylation of CDC2.
- Recombinant CDC25 phosphatase dephosphorylates and activates inactive CDC2 kinase in vitro.
- Inactive CDC2 kinase from treated cells serves as a sensitive substrate for a CDC25 phosphatase assay.
Conclusions:
- CDC25 phosphatase plays a key role in reactivating CDC2 kinase after DNA damage-induced arrest.
- A novel, sensitive assay utilizing Etoposide-treated cell CDC2 as a substrate for CDC25 phosphatase has been established.
- This assay offers a physiological approach for screening antimitotic drugs.