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Oligomerization is not essential for growth suppression by p53 in p53-deficient osteosarcoma Saos-2 cells
C Ishioka1, H Shimodaira, C Englert
1Department of Clinical Oncology, Tohoku University, Sendai, Japan. chikashi@idac.tohoku.ac.jp
Abstract:
The carboxy-terminal portion of the p53 protein contains the tetramerization domain, and the introduction of multiple missense mutations in this domain disrupts the formation of p53 tetramers, resulting in the production of dimeric or monomeric forms of p53. It has recently been shown that a single missense or nonsense mutation in this domain affects the functional properties of p53 both in yeast and in mammalian cells. In this study, we tested the oligomerization of p53 with mutations in the oligomerization domain, when expressed in a human osteosarcoma cell line, Saos-2, in vivo. We found that single point mutations, including two missense and two nonsense mutations, in the alpha-helix of the oligomerization domain disrupted the oligomerization of p53, but that p53 still retained its ability to inhibit colony formation of cells to some degree. These results suggest that oligomerization and the carboxy-terminal basic domain are not prerequisite for p53-dependent tumor suppression, and this may explain why few of the tumor-derived p53 mutations that have been examined so far are carboxy-terminal mutations.
Insights
p53 protein mutations in the oligomerization domain disrupt tetramer formation but retain some tumor suppression ability. This suggests p53 oligomerization is not essential for its tumor suppressor function.
Area of Science:
- Molecular Biology
- Cancer Research
- Protein Structure and Function
Background:
- The p53 protein's carboxy-terminal region includes the tetramerization domain, crucial for forming active p53 tetramers.
- Mutations in this domain can lead to non-tetrameric p53 forms (dimers or monomers), impacting its function.
- Previous studies indicate even single mutations in the oligomerization domain affect p53 activity in various cell types.
Purpose of the Study:
- To investigate the in vivo effects of mutations within the p53 oligomerization domain on p53 oligomerization and tumor suppressor activity.
- To determine if p53 oligomerization is a prerequisite for its tumor suppression function.
Main Methods:
- Expression of p53 with specific mutations in the oligomerization domain within the Saos-2 human osteosarcoma cell line.
- Assessment of p53 oligomerization status in vivo.
- Evaluation of the impact of these mutations on p53's ability to inhibit colony formation.
Main Results:
- Single point mutations (missense and nonsense) in the alpha-helix of the p53 oligomerization domain disrupted p53 oligomerization.
- Despite disrupted oligomerization, mutated p53 retained a partial ability to inhibit colony formation.
- These findings challenge the necessity of p53 tetramerization for its tumor suppressor activity.
Conclusions:
- p53 oligomerization and the carboxy-terminal basic domain are not strictly required for p53-dependent tumor suppression.
- This explains the lower frequency of carboxy-terminal p53 mutations observed in tumors.