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The mitotic peptidyl-prolyl isomerase, Pin1, interacts with Cdc25 and Plx1
D G Crenshaw1, J Yang, A R Means
1Department of Pharmacology and Cancer Biology, Box 3686, Duke University Medical Center, C366 LSRC, Research Drive, Durham, NC 27710, USA.
Abstract:
The cis/trans peptidyl-prolyl isomerase, Pin1, is a regulator of mitosis that is well conserved from yeast to man. Here we demonstrate that depletion of Pin1-binding proteins from Xenopus egg extracts results in hyperphosphorylation and inactivation of the key mitotic regulator, Cdc2/cyclin B. We show biochemically that this phenotype is a consequence of Pin1 interaction with critical upstream regulators of Cdc2/cyclin B, including the Cdc2-directed phosphatase, Cdc25, and its known regulator, Plx1. Although Pin1 could interact with Plx1 during interphase and mitosis, only the phosphorylated, mitotically active form of Cdc25 was able to bind Pin1, an event we have recapitulated using in vitro phosphorylated Cdc25. Taken together, these data suggest that Pin1 may modulate cell cycle control through interaction with Cdc25 and its activator, Plx1.
Insights
Pin1, a mitotic regulator, interacts with Cdc25 and Plx1. Depleting Pin1-binding proteins causes hyperphosphorylation and inactivation of Cdc2/cyclin B, suggesting Pin1 modulates cell cycle control.
Area of Science:
- Molecular Biology
- Cell Cycle Regulation
Background:
- Pin1 (peptidyl-prolyl isomerase) is a conserved regulator of mitosis.
- Pin1's role in regulating key cell cycle proteins is not fully understood.
Purpose of the Study:
- To investigate the role of Pin1-binding proteins in regulating Cdc2/cyclin B activity.
- To elucidate the mechanism by which Pin1 influences mitotic progression.
Main Methods:
- Xenopus egg extracts were used to deplete Pin1-binding proteins.
- Biochemical assays were performed to analyze protein phosphorylation and interactions.
- In vitro phosphorylation assays were used to study Pin1-Cdc25 binding.
Main Results:
- Depletion of Pin1-binding proteins led to hyperphosphorylation and inactivation of Cdc2/cyclin B.
- Pin1 was found to interact with Cdc25 and Plx1, regulators of Cdc2/cyclin B.
- Pin1 specifically binds to the phosphorylated, active form of Cdc25.
Conclusions:
- Pin1 modulates cell cycle control by interacting with Cdc25 and its activator, Plx1.
- Pin1's interaction with phosphorylated Cdc25 is crucial for regulating mitotic progression.