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Regulation of Saccharomyces cerevisiae CDC7 function during the cell cycle
H J Yoon1, S Loo, J L Campbell
1Braun Laboratories, California Institute of Technology, Pasadena 91125.
Molecular Biology of the Cell
|February 1, 1993
Summary
Yeast Cdc7 kinase activity is cell-cycle regulated and controlled by phosphorylation, crucial for the G1/S transition. This periodic activation ensures proper cell cycle progression through START.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- The yeast Cdc7 protein kinase is essential for the G1/S cell cycle transition.
- Cdc7 function is linked to passage through START, a critical cell cycle checkpoint.
- Cdc28/cdc2/p34 protein kinase regulates the START transition.
Purpose of the Study:
- To investigate the cell cycle regulation of yeast Cdc7 protein kinase activity.
- To determine the role of phosphorylation in the activation of Cdc7 kinase.
- To elucidate the factors contributing to the complex phosphorylation pattern of Cdc7.
Main Methods:
- Cell cycle arrest and extract preparation.
- In vitro kinase assays and phosphatase treatment.
- Phosphopeptide mapping and site-directed mutagenesis.
Main Results:
- Yeast Cdc7 kinase activity fluctuates during the cell cycle, while protein levels remain constant.
- Cdc7 kinase is activated by phosphorylation and inactivated by dephosphorylation.
- Cdc7 protein is hypophosphorylated and inactive at START, becoming active and highly phosphorylated after passing START.
- Both autophosphorylation and trans-phosphorylation contribute to Cdc7's phosphorylation pattern.
- Cdc28 kinase phosphorylation site is important for the overall Cdc7 phosphorylation pattern.
Conclusions:
- Yeast Cdc7 kinase activity is periodically regulated by phosphorylation, ensuring proper cell cycle progression.
- Phosphorylation by Cdc28 kinase plays a significant role in modulating Cdc7 activity.
- Understanding Cdc7 regulation provides insights into cell cycle control mechanisms.