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Tumor suppressor p53 protein is a new target for the metastasis-associated Mts1/S100A4 protein: functional
M Grigorian1, S Andresen, E Tulchinsky
1Department of Molecular Cancer Biology, Institute of Cancer Biology, Danish Cancer Society, Strandboulevarden 49, DK-2100 Copenhagen Ø, Denmark. mg@cancer.dk
Abstract:
A physical and functional interaction between the Ca(2+)-binding protein Mts1 (S100A4) and the tumor suppressor p53 protein is shown here for the first time. We demonstrate that Mts1 binds to the extreme end of the C-terminal regulatory domain of p53 by several in vitro and in vivo approaches: co-immunoprecipitation, affinity chromatography, and far Western blot analysis. The Mts1 protein in vitro inhibits phosphorylation of the full-length p53 and its C-terminal peptide by protein kinase C but not by casein kinase II. The Mts1 binding to p53 interferes with the DNA binding activity of p53 in vitro and reporter gene transactivation in vivo, and this has a regulatory function. A differential modulation of the p53 target gene (p21/WAF, bax, thrombospondin-1, and mdm-2) transcription was observed upon Mts1 induction in tet-inducible cell lines expressing wild type p53. Mts1 cooperates with wild type p53 in apoptosis induction. Our data imply that the ability of Mts1 to enhance p53-dependent apoptosis might accelerate the loss of wild type p53 function in tumors. In this way, Mts1 can contribute to the development of a more aggressive phenotype during tumor progression.
Insights
The calcium-binding protein Mts1 (S100A4) physically interacts with and inhibits the tumor suppressor p53 protein. This interaction disrupts p53
Area of Science:
- Molecular Biology
- Cancer Research
- Cell Biology
Background:
- The tumor suppressor p53 protein plays a critical role in preventing cancer.
- Mts1 (S100A4) is a calcium-binding protein implicated in tumor progression.
- The interaction between Mts1 and p53 has not been previously established.
Purpose of the Study:
- To investigate the physical and functional interaction between Mts1 and p53.
- To elucidate the mechanism by which Mts1 affects p53 activity.
- To determine the role of the Mts1-p53 interaction in tumor development.
Main Methods:
- Co-immunoprecipitation
- Affinity chromatography
- Far Western blot analysis
- In vitro kinase assays
- Reporter gene assays
- Analysis of p53 target gene transcription
Main Results:
- Mts1 directly binds to the C-terminal regulatory domain of p53.
- Mts1 inhibits p53 phosphorylation by protein kinase C.
- Mts1 binding impairs p53 DNA binding and transactivation activity.
- Mts1 differentially modulates the transcription of p53 target genes.
- Mts1 enhances p53-dependent apoptosis.
Conclusions:
- Mts1 physically and functionally interacts with p53.
- Mts1 acts as a negative regulator of p53 activity.
- Mts1-mediated inhibition of p53 may contribute to tumor progression and a more aggressive phenotype.