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Myt1: a membrane-associated inhibitory kinase that phosphorylates Cdc2 on both threonine-14 and tyrosine-15
P R Mueller1, T R Coleman, A Kumagai
1Division of Biology 216-76, Howard Hughes Medical Institute, California Institute of Technology, Pasadena 91125, USA.
Abstract:
Cdc2 is the cyclin-dependent kinase that controls entry of cells into mitosis. Phosphorylation of Cdc2 on threonine-14 and tyrosine-15 inhibits the activity of the enzyme and prevents premature initiation of mitosis. Although Wee1 has been identified as the kinase that phosphorylates tyrosine-15 in various organisms, the threonine-14-specific kinase has not been isolated. A complementary DNA was cloned from Xenopus that encodes Myt1, a member of the Wee1 family that was discovered to phosphorylate Cdc2 efficiently on both threonine-14 and tyrosine-15. Myt1 is a membrane-associated protein that contains a putative transmembrane segment. Immunodepletion studies suggested that Myt1 is the predominant threonine-14-specific kinase in Xenopus egg extracts. Myt1 activity is highly regulated during the cell cycle, suggesting that this relative of Wee1 plays a role in mitotic control.
Insights
Researchers identified Myt1, a novel Wee1 family kinase, crucial for regulating cell cycle entry into mitosis. Myt1 phosphorylates Cdc2 on threonine-14 and tyrosine-15, inhibiting its activity and preventing premature mitosis.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Cdc2 kinase activity controls cell cycle progression into mitosis.
- Phosphorylation at threonine-14 and tyrosine-15 inhibits Cdc2 activity, preventing premature mitosis.
- While Wee1 phosphorylates tyrosine-15, the threonine-14 kinase remained unidentified.
Purpose of the Study:
- To identify the kinase responsible for threonine-14 phosphorylation of Cdc2.
- To characterize the function and regulation of this novel kinase in mitotic control.
Main Methods:
- Cloning of complementary DNA encoding Myt1 from Xenopus.
- Biochemical assays to assess Myt1's kinase activity on Cdc2.
- Immunodepletion studies in Xenopus egg extracts.
Main Results:
- Xenopus Myt1, a Wee1 family member, efficiently phosphorylates Cdc2 on both threonine-14 and tyrosine-15.
- Myt1 is a membrane-associated protein.
- Myt1 is the predominant threonine-14-specific kinase in Xenopus egg extracts.
- Myt1 activity is cell cycle-regulated.
Conclusions:
- Myt1 is a key regulator of mitotic entry by phosphorylating Cdc2 at both inhibitory sites.
- Myt1's cell cycle-dependent activity suggests a critical role in controlling the timing of mitosis.