Related Experiment Videos
Wild-type p53 can down-modulate the activity of various promoters
D Ginsberg1, F Mechta, M Yaniv
1Department of Chemical Immunology, Weizmann Institute of Science, Rehovot, Israel.
Abstract:
The wild-type (wt) p53 protein is the product of a tumor suppressor gene that is a frequent target for inactivation in many types of tumors. The nuclear localization of the protein, as well as additional features, suggest that it may be involved in the regulation of gene expression. To explore this possibility, the effects of overproduced wt p53 were investigated in a number of systems. Induction of growth arrest via the antiproliferative effect of wt p53 greatly impaired the ability of cells to exhibit an increase in c-fos mRNA upon serum stimulation. Experiments in which cells were cotransfected with p53 expression plasmids together with a reporter gene linked to various promoters revealed that wt p53 could effectively reduce transcription from a series of promoters derived from serum-inducible genes, but not from a major histocompatibility complex gene. The p53-mediated repression of c-fos gene expression occurred even in the presence of cycloheximide. Kinetic studies indicate that the effect of wt p53 is rapid, rather than representing a secondary consequence of growth arrest. These findings support a role for p53 in transcriptional regulation, perhaps by reducing the expression of genes that are needed for ongoing cell proliferation.
Insights
Wild-type p53 protein, a tumor suppressor, regulates gene expression by inhibiting transcription of proliferation-related genes like c-fos. This antiproliferative effect occurs rapidly and independently of cell cycle arrest.
Area of Science:
- Molecular Biology
- Cancer Biology
- Gene Regulation
Background:
- The wild-type p53 protein is a crucial tumor suppressor.
- p53's nuclear localization suggests a role in gene expression regulation.
- Inactivation of p53 is common in many cancers.
Purpose of the Study:
- To investigate the role of wild-type p53 in transcriptional regulation.
- To determine if p53 affects the expression of serum-inducible genes.
- To explore the mechanism and kinetics of p53's effect on gene expression.
Main Methods:
- Overproduction of wild-type p53 in various cell systems.
- Assessing c-fos mRNA levels after serum stimulation.
- Reporter gene assays with promoters from serum-inducible genes and MHC genes.
- Experiments conducted in the presence of cycloheximide.
- Kinetic studies of p53's transcriptional effects.
Main Results:
- Wild-type p53 induction of growth arrest impaired c-fos mRNA increase upon serum stimulation.
- p53 significantly repressed transcription from serum-inducible gene promoters but not MHC gene promoters.
- p53-mediated repression of c-fos expression was observed even with cycloheximide.
- The transcriptional regulatory effect of p53 was rapid, not a secondary effect of growth arrest.
Conclusions:
- Wild-type p53 plays a role in transcriptional regulation.
- p53 may function by downregulating genes essential for cell proliferation.
- These findings highlight p53's importance in controlling cell growth and preventing tumor formation.