Mammalian p53 can function as a transcription factor in yeast

Area of Science:

• Molecular Biology
• Yeast Genetics
• Cancer Research

Background:

• The p53 protein is a critical tumor suppressor involved in cellular responses to stress.
• p53 possesses a transactivation domain and binds to specific DNA sequences.
• Previous studies utilized GAL4 fusion proteins and immunoprecipitation assays to investigate p53 functions.

Purpose of the Study:

• To investigate the transcriptional activation function of mammalian p53 in yeast.
• To assess the impact of common human tumor-associated p53 mutations on transcriptional activity.
• To develop a yeast-based transcription assay for detecting p53 mutations.

Main Methods:

• Expressing mammalian p53 in Saccharomyces cerevisiae (yeast).
• Utilizing a CYC1 hybrid promoter with a p53-binding sequence linked to a reporter gene.
• Introducing specific p53 mutations (175H, 248W, 273H, 285K) and murine p53 variants.
• Employing a yeast transfection assay with p53 PCR products and X-gal screening.

Main Results:

• Mammalian p53 activated reporter gene transcription in yeast, dependent on binding site orientation and copy number.
• Human p53 mutants (175H, 248W, 273H) lost transcriptional activation ability.
• Human p53 mutant 285K and murine p53 showed temperature-sensitive transcriptional activation.
• Murine p53 mutant 135V exhibited temperature-sensitive transcriptional activation.
• Transcriptional competence correlated better with mutation status than antibody-determined structure.

Conclusions:

• Yeast can serve as a model system to study p53 transcriptional activity and the effects of mutations.
• Loss of transcriptional function in specific p53 mutants is a reliable indicator of mutation.
• A simple yeast transcription assay using X-gal screening can effectively detect p53 mutations.