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Reactivation of mutant p53 by a one-hybrid adaptor protein
Judith Roth1, Claudia Lenz-Bauer, Ana Contente
1Abteilung für Gastroenterologie und Stoffwechsel, Klinikum der Philipps-Universität Marburg, Baldingerstrasse, 35043 Marburg, Germany.
Abstract:
The most frequent genetic alteration in cancer is a mutation of p53. In most cases, this leads to a sharp increase of the p53 protein levels but abolishes p53's function as an activator of transcription. To correct this defect, wild-type p53 is being reintroduced into tumor cells through gene therapy vectors, thereby inducing cell death. However, this effect is not necessarily specific for tumor cells. Furthermore, mutant p53 in tumor cells trans-dominantly impairs the function of wild-type p53. As an approach to overcome these obstacles, we have developed an adaptor protein that reactivates mutant p53 rather than stimulating transcription on its own. The DNA binding and tetramerizing portions of the p53-homologue p73 were fused to the oligomerization domain of p53. This chimera binds to the DNA of p53-responsive promoters through the p73-derived portions, and it binds to mutant p53 by the p53-derived oligomerization domain. Through this one-hybrid system, mutant p53 is re-enabled to activate transcription. When the adaptor was expressed in tumor cells that contain mutant p53, expression of p53-responsive genes was activated, and growth was inhibited. No such effects were observed in cells that contain wild-type p53 or no p53 at all. When the adaptor was expressed through an adenovirus vector, tumor cells containing mutant p53 were specifically induced to undergo apoptosis. This strategy can turn mutant p53 into an inhibitor of tumor cell growth and might enable gene therapy to eliminate cancer cells with specificity.
Insights
This study developed an adaptor protein to reactivate mutant p53, a common cancer gene. This approach specifically inhibits tumor cell growth and induces apoptosis in cancer cells with mutant p53.
Area of Science:
- Molecular Biology
- Cancer Genetics
- Gene Therapy
Background:
- TP53 mutations are the most common genetic alteration in cancer, leading to increased but non-functional p53 protein.
- Current gene therapy approaches reintroducing wild-type p53 lack tumor specificity and can be hindered by mutant p53's trans-dominant effects.
Purpose of the Study:
- To develop a novel strategy to specifically target and inhibit tumor cells harboring mutant p53.
- To create an adaptor protein that reactivates mutant p53's transcriptional activity.
Main Methods:
- A chimeric adaptor protein was engineered by fusing the DNA-binding domain of p73 to the oligomerization domain of p53.
- This adaptor protein functions as a one-hybrid system, binding to p53-responsive promoters and mutant p53.
- Adenovirus vectors were used to express the adaptor protein in tumor cells.
Main Results:
- The adaptor protein successfully reactivated mutant p53, leading to the activation of p53-responsive genes and inhibition of tumor cell growth.
- Specificity was demonstrated as no effects were observed in cells with wild-type or no p53.
- Adenovirus-mediated expression specifically induced apoptosis in tumor cells with mutant p53.
Conclusions:
- The developed adaptor protein strategy effectively converts mutant p53 into a tumor suppressor.
- This approach offers a specific gene therapy strategy for eliminating cancer cells with mutant p53.
- Reactivating mutant p53 holds promise for targeted cancer treatment.