Related Experiment Videos
Mutant p53 and aberrant cytosine methylation cooperate to silence gene expression
Marc M Oshiro1, George S Watts, Ryan J Wozniak
1Bone Marrow Transplant Program, Arizona Cancer Center and Department of Pharmacology & Toxicology, The University of Arizona, Tucson, AZ 85724, USA.
Abstract:
p53 is an important transcriptional regulator that is frequently mutated in cancer. Gene-profiling experiments of breast cancer cells infected with wt p53 revealed both MASPIN and desmocollin 3 (DSC3) to be p53-target genes, even though both genes are silenced in association with aberrant cytosine methylation of their promoters. Despite the transcriptional repression of these genes by aberrant DNA methylation, restoration of p53 resulted in the partial reactivation of both genes. This reactivation is a result of wt p53 binding to its consensus DNA-binding sites within the MASPIN and DSC3 promoters, stimulating histone acetylation, and enhancing chromatin accessibility of their promoters. Interestingly, wt p53 alone did not affect the methylation status of either promoter, suggesting that p53 itself can partially overcome the repressive barrier of DNA methylation. Pharmacologic inhibition of DNA methylation with 5-aza-2'-deoxycytidine in combination with restoration of wt p53 status resulted in a synergistic reactivation of these genes to near-normal levels. These results suggest that cancer treatments that target both genetic and epigenetic facets of gene regulation may be a useful strategy towards the therapeutic transcriptional reprogramming of cancer cells.
Insights
Wild-type p53 partially reactivates silenced cancer genes MASPIN and DSC3 by altering chromatin accessibility, even with promoter DNA methylation. Combining p53 restoration with DNA methylation inhibitors synergistically restores gene expression.
Area of Science:
- Molecular Biology
- Cancer Genetics
- Epigenetics
Background:
- p53 is a key transcriptional regulator frequently mutated in various cancers.
- MASPIN and desmocollin 3 (DSC3) are identified as p53 target genes in breast cancer.
- Aberrant cytosine methylation of gene promoters silences MASPIN and DSC3, contributing to cancer progression.
Purpose of the Study:
- To investigate the mechanism by which wild-type p53 reactivates transcriptionally silenced genes (MASPIN and DSC3) in breast cancer cells.
- To determine if p53 can overcome the repressive effects of promoter DNA methylation.
- To evaluate the synergistic effect of p53 restoration and DNA methylation inhibition on gene reactivation.
Main Methods:
- Gene-profiling experiments in breast cancer cells.
- Analysis of p53 binding to MASPIN and DSC3 promoters.
- Assessment of histone acetylation and chromatin accessibility.
- Pharmacologic inhibition of DNA methylation using 5-aza-2'-deoxycytidine.
Main Results:
- Wild-type p53 partially reactivated MASPIN and DSC3 expression despite promoter DNA methylation.
- p53 binding stimulated histone acetylation and increased chromatin accessibility at target promoters.
- p53 alone did not alter promoter methylation status.
- Combined treatment with p53 restoration and 5-aza-2'-deoxycytidine resulted in synergistic gene reactivation.
Conclusions:
- Wild-type p53 can partially overcome DNA methylation-mediated transcriptional repression through epigenetic modifications.
- Targeting both genetic (p53) and epigenetic (DNA methylation) factors offers a promising strategy for cancer therapy.
- Therapeutic transcriptional reprogramming of cancer cells may involve combined genetic and epigenetic approaches.