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The interferon-inducible murine p48 (ISGF3gamma) gene is regulated by protooncogene c-myc
X Weihua1, D J Lindner, D V Kalvakolanu
1Marlene and Stewart Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
Abstract:
p48 protein is an integral component of the multimeric interferon (IFN)-regulated transcription factor, ISGF3. We have shown earlier that this gene is regulated by a novel IFN-gamma-regulated element. In addition to the IFN-regulated element, a myc-max binding site is also present in this promoter. In this investigation we have studied the role of this site in the regulation of the p48 gene. In serum-induced quiescent cells Myc up-regulated the expression of p48 mRNA. We show that the protooncogene Myc regulates the expression of p48 through the element CACGTG. Mutations in this motif abolish Myc-inducibility of the reporter genes carrying p48 promoter elements. Purified Myc and Max proteins interact with the Myc-stimulated element of the p48 promoter. We also show that cells lacking p48 expression are highly susceptible to the cytocidal action of anticancer drugs. Taken together these data suggest that p48 may function as an anti-stress cell survival factor.
Insights
The protooncogene Myc regulates p48 gene expression via a specific DNA binding site. This regulation suggests p48 acts as an anti-stress cell survival factor, impacting cancer drug sensitivity.
Area of Science:
- Molecular Biology
- Cellular Biology
- Genetics
Background:
- The p48 protein is a key component of the interferon (IFN)-regulated transcription factor ISGF3.
- Previous studies identified a novel IFN-gamma-regulated element controlling the p48 gene.
- A Myc-Max binding site was also identified in the p48 promoter region.
Purpose of the Study:
- To investigate the role of the Myc-Max binding site in regulating p48 gene expression.
- To determine if the protooncogene Myc influences p48 expression.
- To explore the functional significance of p48 in cellular stress response and drug sensitivity.
Main Methods:
- Reporter gene assays were used to assess promoter activity.
- Site-directed mutagenesis was employed to study the Myc-Max binding site (CACGTG motif).
- Electrophoretic mobility shift assays (EMSAs) were performed with purified Myc and Max proteins.
Main Results:
- Myc significantly up-regulated p48 mRNA expression in serum-induced quiescent cells.
- Mutations within the CACGTG motif abolished Myc-induced reporter gene expression.
- Purified Myc and Max proteins demonstrated binding to the Myc-stimulated element on the p48 promoter.
- Cells deficient in p48 expression exhibited increased susceptibility to the cytotoxic effects of anticancer drugs.
Conclusions:
- The protooncogene Myc regulates p48 gene expression through the CACGTG binding site.
- p48 protein likely functions as an anti-stress cell survival factor.
- p48 expression levels influence cellular resistance to anticancer therapies.