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Wild-type p53-mediated induction of rat mdr1b expression by the anticancer drug daunorubicin
1Department of Molecular Pathology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
Abstract:
The expression of P-glycoproteins encoded by the mdr gene family is associated with the emergence of the multidrug resistance phenotype in animal cells. mdr expression can be induced by many extracellular stimulants including cytotoxic drugs and chemical carcinogens. However, little is known about the mechanisms involved. Here, we report that the expression of the rat mdr1b can be induced by anticancer drug daunorubicin. Further analysis identified a bona fide p53-binding site spanning from base pairs -199 to -180 (5'-GAACATGTAGAGACATGTCT-3') in the rat mdr1b promoter that is essential for basal and daunorubicin-inducible promoter activities. In addition, our results show that wild-type p53 can up-regulate not only the promoter function but also endogenous expression of the rat mdr1b. To the best of our knowledge, this is the first report showing that a specific p53-binding site is involved in the transcriptional regulation of mdr gene by wild-type p53. Since p53 is a sensor for a wide variety of genotoxic stresses, our finding has broad implications for understanding the mechanisms involved in the inducible expression of mdr gene by anticancer drugs, chemical carcinogens, UV light, and other DNA-damaging agents.
Insights
Wild-type p53 up-regulates the rat mdr1b gene, a key factor in multidrug resistance. A specific p53-binding site in the mdr1b promoter is crucial for this induction by anticancer drugs like daunorubicin.
Area of Science:
- Molecular Biology
- Genetics
- Cancer Research
Background:
- The multidrug resistance (MDR) phenotype in animal cells is linked to P-glycoprotein expression from the mdr gene family.
- MDR gene expression can be triggered by various external factors, including cytotoxic drugs and chemical carcinogens, but the underlying mechanisms remain unclear.
Purpose of the Study:
- To investigate the mechanisms of inducible mdr gene expression.
- To identify the role of p53 in the regulation of the rat mdr1b gene.
Main Methods:
- Reporter assays were used to analyze the rat mdr1b promoter activity.
- Site-directed mutagenesis identified a critical p53-binding site.
- Western blotting and quantitative PCR assessed endogenous mdr1b expression.
Main Results:
- Anticancer drug daunorubicin induces the expression of rat mdr1b.
- A functional p53-binding site (-199 to -180) in the rat mdr1b promoter is essential for basal and daunorubicin-inducible activity.
- Wild-type p53 significantly enhances both promoter function and endogenous rat mdr1b expression.
Conclusions:
- This study reveals a direct role for wild-type p53 in the transcriptional regulation of the rat mdr1b gene via a specific promoter-binding site.
- The findings provide crucial insights into the inducible expression of mdr genes in response to DNA-damaging agents, including anticancer drugs and carcinogens.