Related Experiment Videos
Wild-type p53 inhibits protein kinase CK2 activity
1Medical Biochemistry and Molecular Biology, University of the Saarland, D-66424 Homburg, Germany.
Abstract:
The growth suppressor protein p53 and the protein kinase CK2 are both implicated in cellular growth regulation. We previously found that p53 binds to protein kinase CK2 via its regulatory beta-subunit. In the present study, we analyzed the consequences of the binding of p53 to CK2 for the enzymatic activity of CK2 in vitro and in vivo. We found that the carboxy-terminus of p53 which is a potent transforming agent stimulated CK2 activity whereas full length wild-type p53 which is a growth suppressor inhibited the activity of protein kinase CK2. Inhibition of protein kinase CK2 by p53 was dose-dependent and was seen for various CK2 substrates. Experiments with heat-denatured p53 and the conformational mutant p53(R175H) revealed that an intact conformation of p53 seemed to be necessary. Transfection of wild-type and of mutant p53 into p53-/- cells showed that the inhibition of p53 on CK2 activity was also detectable in intact cells and specific for wild-type p53 indicating that the growth suppressing function of p53 might at least be partially achieved by down-regulation of protein kinase CK2.
Insights
Wild-type p53 protein inhibits protein kinase CK2 activity, while a mutated form stimulates it. This finding suggests p53
Area of Science:
- Molecular Biology
- Cellular Regulation
- Biochemistry
Background:
- Protein p53 and protein kinase CK2 are key regulators of cellular growth.
- Previous research established a binding interaction between p53 and CK2's beta-subunit.
Purpose of the Study:
- To investigate the impact of p53 binding on the enzymatic activity of protein kinase CK2.
- To determine if p53's growth-suppressing function involves modulation of CK2 activity.
Main Methods:
- In vitro enzymatic assays using various CK2 substrates.
- In vivo studies involving transfection of wild-type and mutant p53 into p53-deficient cells.
- Analysis of protein conformation using heat-denatured and mutant p53.
Main Results:
- The carboxy-terminus of p53 stimulated CK2 activity, whereas full-length wild-type p53 inhibited it.
- p53 inhibition of CK2 was dose-dependent and required an intact p53 conformation.
- Inhibition of CK2 by wild-type p53 was observed in intact cells, suggesting a role in growth suppression.
Conclusions:
- Wild-type p53 inhibits protein kinase CK2 activity in a conformation-dependent manner.
- Down-regulation of protein kinase CK2 activity by p53 may contribute to its growth-suppressing function.
- These findings elucidate a novel mechanism for p53-mediated cellular growth regulation.