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Published on: August 16, 2015
Speedy: a novel cell cycle regulator of the G2/M transition
J L Lenormand1, R W Dellinger, K E Knudsen
1Department of Chemistry and Biochemistry, Center for Molecular Genetics, University of California, San Diego, La Jolla, CA 92093-0367, USA.
Abstract:
Stage VI Xenopus oocytes are suspended at the G2/M transition of meiosis I, and represent an excellent system for the identification and examination of cell cycle regulatory proteins. Essential cell cycle regulators such as MAPK, cyclins and mos have the ability to induce oocyte maturation, causing the resumption of the cell cycle from its arrested state. We have identified the product of a novel Xenopus gene, Speedy or Spy1, which is able to induce rapid maturation of Xenopus oocytes, resulting in the induction of germinal vesicle breakdown (GVBD) and activation of M-phasepromoting factor (MPF). Spy1 activates the MAPK pathway in oocytes, and its ability to induce maturation is dependent upon this pathway. Spy1-induced maturation occurs much more rapidly than maturation induced by other cell cycle regulators including progesterone, mos or Ras, and does not require any of these proteins or hormones, indicating that Spy1-induced maturation proceeds through a novel regulatory pathway. In addition, we have shown that Spy1 physically interacts with cdk2, and prematurely activates cdk2 kinase activity. Spy1 therefore represents a novel cell cycle regulatory protein, inducing maturation through the activation of MAPK and MPF, and also leading to the premature activation of cdk2.
Insights
A novel protein, Speedy (Spy1), rapidly matures Xenopus oocytes by activating MAPK and MPF pathways. Spy1 also prematurely activates cdk2, suggesting a new cell cycle regulatory mechanism.
Area of Science:
- Cell Biology
- Molecular Biology
- Developmental Biology
Background:
- Xenopus oocytes arrest at meiosis I G2/M transition, serving as a model for cell cycle regulation.
- Key regulators like MAPK, cyclins, and mos induce oocyte maturation and cell cycle resumption.
Purpose of the Study:
- Identify novel cell cycle regulatory proteins in Xenopus oocytes.
- Investigate the function and mechanism of the Speedy (Spy1) protein.
Main Methods:
- Utilized Xenopus oocyte system to study cell cycle regulation.
- Analyzed the effect of Speedy (Spy1) on oocyte maturation, MAPK pathway, and MPF activation.
- Assessed Spy1 interaction with cdk2 and its kinase activity.
Main Results:
- Speedy (Spy1) rapidly induces Xenopus oocyte maturation, germinal vesicle breakdown (GVBD), and MPF activation.
- Spy1 activates the MAPK pathway, which is essential for its maturation-inducing effect.
- Spy1 interacts with cdk2, leading to premature cdk2 kinase activity.
- Spy1-induced maturation is faster than other known regulators and does not require progesterone, mos, or Ras.
Conclusions:
- Speedy (Spy1) is a novel cell cycle regulator that induces oocyte maturation via MAPK and MPF activation.
- Spy1 represents a new pathway for cell cycle regulation, distinct from known pathways.
- Spy1's interaction with and premature activation of cdk2 highlight its unique role in cell cycle control.
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