Related Experiment Videos
The p16(INK4A) protein and flavopiridol restore yeast cell growth inhibited by Cdk4
M Moorthamer1, M Panchal, W Greenhalf
1Oncology Research, Novartis Pharma AG, Basel, Switzerland.
Abstract:
Cyclin-dependent kinase 4 (Cdk4) activity is misregulated in most cancers. Loss of Cdk4 regulation can occur through overexpression of Cdk4 catalytic subunit or its regulatory partner cyclin D1, or if the Cdk4-specific inhibitory protein p16(INK4A) is inactive. We have attempted to express the two human subunits, Cdk4 and cyclin D1, in the yeast Saccharomyces cerevisiae. Surprisingly, expression of Cdk4 alone, under control of the strong GAL promoter, inhibits cell growth. Coexpression of both subunits allows formation of an active Cdk4-cyclin D1 complex which accentuates growth arrest. In cells expressing Cdk4 only, growth is restored by overexpressing human Cdc37, a Cdk4-binding molecular chaperone. Interestingly, the effect of Cdk4 on yeast is also overcome by both p16- and p21-families of Cdk-inhibitory proteins. Moreover, flavopiridol, a compound which inhibits Cdk4 enzyme activity, restores cell division. The fact that p16(INK4A) and flavopiridol negate Cdk4-mediated suppression of yeast cell growth implies that this simple system can be used as a screen for identifying Cdk4-specific antagonists which may mimic p16(INK4A) in the cancer cell cycle.
Insights
Researchers developed a yeast model to study cancer-related Cyclin-dependent kinase 4 (Cdk4). This system can screen for Cdk4 inhibitors, potentially aiding in cancer therapy development.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Cyclin-dependent kinase 4 (Cdk4) dysregulation is common in cancers.
- This can result from Cdk4 or cyclin D1 overexpression, or p16(INK4A) inactivation.
Purpose of the Study:
- To express human Cdk4 and cyclin D1 in yeast Saccharomyces cerevisiae.
- To establish a novel screening system for Cdk4 inhibitors.
Main Methods:
- Expression of human Cdk4 and cyclin D1 in yeast.
- Assessing cell growth inhibition and restoration.
- Utilizing molecular chaperones and Cdk inhibitors.
Main Results:
- Cdk4 expression alone inhibited yeast growth.
- Coexpression of Cdk4 and cyclin D1 exacerbated growth arrest.
- Yeast growth was restored by human Cdc37, p16/p21 inhibitors, and flavopiridol.
Conclusions:
- Yeast expressing Cdk4 provides a model for studying Cdk4 regulation.
- This system can identify Cdk4-specific antagonists.
- Such antagonists may mimic p16(INK4A) in targeting the cancer cell cycle.