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Human p53 restores DNA synthesis control in fission yeast
M Bureik1, A Jungbluth, R Drescher
1Medical Biochemistry, University of Saarland, Homburg/Saar, Germany.
Abstract:
The p53 gene is the most common target for genetic alterations in human cancers. As a transcriptional regulator p53 enhances the expression of proteins that control cellular proliferation. Although there is no evidence of a p53 homologous gene in yeast, the p53 protein was found to be functional in terms of growth repression and transactivation in yeast, suggesting that some features of p53 function are conserved. Here we report the construction and characterization of a p53 wild type expression strain of fission yeast. Upon induction of wild type p53 expression a dosage dependent growth arrest was observed rendering recipient yeast cells sensitive to UV irradiation in a p53 dosage dependent fashion. The observed growth arrest was efficiently suppressed by coexpression of human CDC25C phosphatase, which restored a normal resistance to UV irradiation in p53 and CDC25C coexpressing yeast cells. Furthermore, expression of CDC25C alone inactivated the DNA synthesis control whereas p53 and CDC25C coexpressing yeast cells showed an intact checkpoint control. Upon moderate expression of wild type p53 a restoration of the DNA synthesis control was also observed in a cdc2.3w mutant background, whereas a tumor mutant of p53 failed to restore this important checkpoint in fission yeast.
Insights
The tumor suppressor p53 protein can regulate cell growth and DNA repair in yeast. Co-expressing p53 with CDC25C phosphatase in fission yeast restored DNA synthesis control and UV resistance.
Area of Science:
- Molecular Biology
- Genetics
- Cancer Research
Background:
- The p53 gene is frequently altered in human cancers.
- p53 acts as a transcriptional regulator controlling cellular proliferation.
- p53 protein exhibits conserved functions in yeast, including growth repression and transactivation.
Purpose of the Study:
- To construct and characterize a fission yeast strain expressing wild-type p53.
- To investigate the effects of p53 expression on yeast cell growth, UV sensitivity, and DNA synthesis control.
- To explore the interaction between p53 and CDC25C phosphatase in regulating cell cycle checkpoints.
Main Methods:
- Generation of a fission yeast strain for inducible wild-type p53 expression.
- Assessment of p53 dosage-dependent effects on cell growth and UV irradiation sensitivity.
- Co-expression experiments with human CDC25C phosphatase to evaluate suppression of p53-induced phenotypes.
- Analysis of DNA synthesis control and checkpoint integrity in response to p53 and CDC25C expression.
Main Results:
- Inducible p53 expression led to a dosage-dependent growth arrest and increased UV sensitivity in fission yeast.
- Co-expression of p53 and CDC25C phosphatase suppressed the growth arrest and restored UV resistance.
- CDC25C alone disrupted DNA synthesis control, while co-expression with p53 maintained checkpoint integrity.
- Wild-type p53, but not a tumor mutant, restored DNA synthesis control in a cdc2.3w mutant background.
Conclusions:
- Fission yeast serves as a model to study conserved p53 functions, including cell cycle regulation.
- p53 and CDC25C interaction is crucial for maintaining DNA synthesis checkpoints and UV resistance.
- The functional integrity of p53 in regulating DNA synthesis checkpoints is demonstrated in yeast.