Related Experiment Videos
p53-dependent association between cyclin G and the B' subunit of protein phosphatase 2A
K Okamoto1, C Kamibayashi, M Serrano
1Howard Hughes Medical Institute, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA.
Abstract:
We and others previously showed that cyclin G is a transcriptional target of the p53 tumor suppressor protein. However, cellular proteins which might form a complex with cyclin G have not yet been identified. To gain insight into the biological role of cyclin G, we used the yeast two-hybrid screen and isolated two mouse cDNAs encoding cyclin G-interacting proteins. Interestingly, both positive cDNAs encoded B' regulatory subunits of protein phosphatase 2A (PP2A). One clone encodes B'alpha, while the other clone codes for a new member of the B' family, B'beta. B'beta is 70% identical to other members of the B' family. B'alpha associated both in vitro and in vivo with cyclin G but not with the other mammalian cyclins. Furthermore, cyclin G formed a complex with B'alpha only after induction of p53 in p53 temperature-sensitive cell lines. These results indicate that cyclin G forms a specific complex with the B' subunit of PP2A and that complex formation is regulated by p53. Potential roles for the cyclin G-B' complex in p53-mediated pathways are discussed.
Insights
Cyclin G, a target of the p53 tumor suppressor, specifically binds to the B
Area of Science:
- Molecular Biology
- Cell Biology
- Cancer Research
Background:
- Cyclin G is a known transcriptional target of the p53 tumor suppressor protein.
- The cellular partners and biological function of cyclin G have remained largely uncharacterized.
Purpose of the Study:
- To identify cellular proteins that interact with cyclin G.
- To elucidate the biological role of cyclin G and its interactions within cellular pathways.
Main Methods:
- Yeast two-hybrid screening was employed to identify cyclin G-interacting proteins.
- In vitro and in vivo association studies were conducted.
- Experiments utilized p53 temperature-sensitive cell lines.
Main Results:
- Two cDNAs encoding B' regulatory subunits of protein phosphatase 2A (PP2A), specifically B'alpha and a novel B'beta, were isolated.
- B'alpha demonstrated specific binding to cyclin G, both in vitro and in vivo, but not to other mammalian cyclins.
- Complex formation between cyclin G and B'alpha was observed to be p53-dependent, occurring after p53 induction.
Conclusions:
- Cyclin G forms a specific complex with the B'alpha subunit of PP2A.
- This complex formation is regulated by the p53 tumor suppressor protein.
- The findings suggest potential roles for the cyclin G-B'alpha complex in p53-mediated cellular processes.