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Studying Proteolysis of Cyclin B at the Single Cell Level in Whole Cell Populations
Published on: September 17, 2012
Directed evolution to bypass cyclin requirements for the Cdc28p cyclin-dependent kinase
K Levine1, L Kiang, M D Jacobson
1Rockefeller University, New York, New York, USA.
Molecular Cell
|October 13, 1999
Summary
Researchers identified cyclin-dependent kinase mutants that bypass the need for CLN genes in yeast cell cycle initiation. This suggests cyclin-independent activity may drive cell cycle progression, challenging current models.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- Cyclin-dependent kinases (CDKs) are crucial regulators of the cell cycle, typically requiring association with cyclins for activity.
- The CLN family of G1 cyclins in yeast (Saccharomyces cerevisiae) are essential for initiating the cell cycle.
- Understanding CDK-cyclin interactions is key to deciphering cell cycle control mechanisms.
Purpose of the Study:
- To identify and characterize cyclin-dependent kinase (CDC28) mutants with altered cyclin requirements.
- To investigate whether cell cycle initiation can occur independently of canonical CLN cyclin interactions.
Main Methods:
- Selection of CDC28 alleles capable of rescuing a yeast strain dependent on a mutated CLN2 cyclin.
- Introduction of further mutations and DNA shuffling to generate CDC28 alleles that bypass CLN gene requirements.
- Gel filtration chromatography to analyze the activity of mutant Cdc28 proteins.
Main Results:
- Mutant CDC28 alleles (CDC28-BYC) were identified that support cell cycle initiation without CLN genes.
- The bypass activity was dependent on the specific CLN2 mutation, indicating a direct interaction or pathway.
- One mutant Cdc28 protein showed kinase activity as a cyclin-free monomer, suggesting constitutive activity.
Conclusions:
- Cyclin-dependent kinase (CDK) targeting by cyclins may not be strictly required for cell cycle initiation.
- Mutant CDKs can exhibit constitutive, cyclin-independent activity, providing a novel mechanism for cell cycle control.
- These findings challenge the universal necessity of cyclin binding for CDK function in cell cycle progression.
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