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Functional cdc25C dual-specificity phosphatase is required for S-phase entry in human cells
Patric Turowski1, Celine Franckhauser, May C Morris
1Cell Biology Unit, Institut de Genetique Humaine, Centre National de la Recherche Scientifique Unité Mixte de Recherche 1142, F-34396 Montpellier, France.
Molecular Biology of the Cell
|July 15, 2003
Summary
The mitotic phosphatase cdc25C is crucial for DNA replication during S-phase. Inhibiting cdc25C halts DNA synthesis, while restoring it reinitiates cell cycle progression.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- The cell cycle involves distinct phases, including DNA replication (S-phase) and mitosis (M-phase).
- cdc25C is a phosphatase known to regulate the G2/M transition.
- Cyclin A is synthesized at the beginning of S-phase, coinciding with cdc25C transcription.
Purpose of the Study:
- To investigate the role of cdc25C in S-phase progression.
- To determine if cdc25C is required for DNA replication.
Main Methods:
- Synchronizing human fibroblasts and HeLa cells.
- Measuring cdc25C protein levels and phosphatase activity.
- Microinjection of antisense-cdc25C molecules.
- Transfection with small interfering RNA (siRNA) against cdc25C.
- Microinjection of wild-type and mutant cdc25C protein.
Main Results:
- cdc25C protein levels and activity significantly increased at S-phase onset.
- Inhibition of cdc25C via antisense or siRNA blocked DNA synthesis and S-phase transit.
- Depletion of cdc25C did not affect cdc25A or cdc25B levels.
- Reintroduction of wild-type cdc25C restored S-phase progression, but a mutant form did not.
Conclusions:
- cdc25C is essential for S-phase progression and DNA replication.
- cdc25C's function in S-phase is distinct from its role in the G2/M transition and from cdc25A.
- These findings highlight a novel role for cdc25C beyond mitosis.