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Determination of S-Phase Duration Using 5-Ethynyl-2'-deoxyuridine Incorporation in Saccharomyces cerevisiae
Published on: October 21, 2022
The yeast mitotic cyclin Clb2 cannot substitute for S phase cyclins in replication origin firing
1Department of Biochemistry, University of Dundee, Scotland, UK. a.d.donaldson@dundee.ac.uk
EMBO Reports
|March 27, 2001
Summary
Cyclin-dependent kinases (CDKs) control cell division. This study reveals that cyclin B2 (Clb2) has distinct specificity, unlike Clb5 and Clb6, failing to activate replication origins crucial for cell cycle progression.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- Cyclin-dependent kinases (CDKs) regulate the cell cycle, including chromosome replication.
- Six B-type cyclins (Clb1-6) in Saccharomyces cerevisiae control S phase and mitosis.
- Clb5 and Clb6 activate early replication origins, while Clb5 also activates late origins.
Purpose of the Study:
- To investigate whether Clb cyclins differ in kinase specificity or merely in expression timing.
- To determine the specific role of Clb2 in activating replication origins during the cell cycle.
Main Methods:
- Genetic analysis in Saccharomyces cerevisiae.
- Conditional expression of Clb2 in cells lacking other cyclins (Clb5, Clb6).
- Assessment of replication origin activation timing and efficiency.
Main Results:
- Expression of Clb2 during S phase did not rescue late origin activation in Clb5-deficient cells.
- Early Clb2 expression failed to restore timely S phase entry in cells lacking Clb5 and Clb6.
- Clb2 demonstrated an inability to drive timely activation of both early and late replication origins.
Conclusions:
- Clb2-directed CDK exhibits a distinct substrate specificity compared to Clb5 and Clb6.
- The timing of Clb cyclin expression is not the sole determinant of their function in replication origin activation.
- Clb2's distinct specificity impacts its role in regulating S phase entry and progression.
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