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p53 regulates a G2 checkpoint through cyclin B1
S A Innocente1, J L Abrahamson, J P Cogswell
1Hamilton Regional Cancer Center, 699 Concession Street, Hamilton, Ontario, Canada L8V 5C2.
Abstract:
The p53 tumor suppressor controls multiple cell cycle checkpoints regulating the mammalian response to DNA damage. To identify the mechanism by which p53 regulates G2, we have derived a human ovarian cell that undergoes p53-dependent G2 arrest at 32 degrees C. We have found that p53 prevents G2/M transition by decreasing intracellular levels of cyclin B1 protein and attenuating the activity of the cyclin B1 promoter. Cyclin B1 is the regulatory subunit of the cdc2 kinase and is a protein required for mitotic initiation. The ability of p53 to control mitotic initiation by regulating intracellular cyclin B1 levels suggests that the cyclin B-dependent G2 checkpoint has a role in preventing neoplastic transformation.
Insights
The p53 tumor suppressor protein prevents cell division by reducing cyclin B1 levels, thereby controlling the G2 checkpoint. This mechanism highlights p53
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- The p53 tumor suppressor is crucial for cellular responses to DNA damage.
- p53 regulates cell cycle checkpoints, including the G2 checkpoint, which controls entry into mitosis.
- Understanding p53's role in G2 arrest is vital for cancer research.
Purpose of the Study:
- To elucidate the mechanism by which p53 regulates the G2 cell cycle phase.
- To identify how p53 influences the transition from G2 to M phase.
Main Methods:
- Derivation of a human ovarian cell line exhibiting p53-dependent G2 arrest at 32°C.
- Analysis of intracellular cyclin B1 protein levels.
- Assessment of cyclin B1 promoter activity.
Main Results:
- p53 was found to inhibit G2/M transition in the derived cell line.
- This inhibition was mediated by decreased intracellular cyclin B1 protein levels.
- p53 also attenuated the activity of the cyclin B1 promoter.
Conclusions:
- p53 controls mitotic initiation by regulating cyclin B1 levels.
- The cyclin B1-dependent G2 checkpoint plays a role in preventing neoplastic transformation.
- This study provides insight into the tumor-suppressive functions of p53.