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Updated: May 10, 2026
12:26
Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay
Published on: May 3, 2018
An essential G1 function for cyclin-like proteins in yeast.
H E Richardson1, C Wittenberg, F Cross
1Department of Molecular Biology, Research Institute of Scripps Clinic, La Jolla, California 92037.
Cell
|December 22, 1989
Summary
Budding yeast cell cycle regulators, cyclins (CLN1, CLN2, CLN3), are essential for G1 phase progression. Their function, likely activating Cdc28 kinase, decays rapidly after biosynthesis ceases, enabling cell proliferation.
Area of Science:
- Molecular Biology
- Cell Biology
- Yeast Genetics
Background:
- Cyclins, initially identified in marine invertebrates for their cell cycle periodicity, are crucial regulators of cell division.
- Three S. cerevisiae genes (CLN1, CLN2, DAF1/WHI1) show homology to cyclins and are implicated in cell cycle progression.
Purpose of the Study:
- To investigate the essential function of CLN1, CLN2, and DAF1/WHI1 gene products in S. cerevisiae cell cycle progression.
- To determine the phase specificity and regulation of Cln protein function.
- To test the hypothesis that Cln proteins activate the Cdc28 protein kinase.
Main Methods:
- Gene deletion studies to assess the impact of CLN1, CLN2, and DAF1/WHI1 loss on cell cycle progression.
- Conditional expression of CLN1 to define the timing and duration of its essential function.
- Analysis of Cln protein function decay after cessation of biosynthesis.
Main Results:
- Mutational elimination of CLN1, CLN2, and DAF1/WHI1 causes cell cycle arrest, while their expression permits proliferation.
- The essential function of Cln proteins is confined to the G1 phase of the cell cycle.
- Cln protein function decays rapidly upon cessation of their synthesis, suggesting a short half-life.
Conclusions:
- Cln proteins are essential for G1 phase progression in S. cerevisiae.
- The data support the hypothesis that Cln proteins activate the Cdc28 protein kinase, crucial for the G1 to S transition.
- DAF1/WHI1 was renamed CLN3 due to functional redundancy with CLN1 and CLN2.
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