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Constitutive mdmx expression during cell growth, differentiation, and DNA damage
1Department of Biochemistry and Molecular Biology, Wright State University, Dayton, Ohio 45435, USA.
DNA and Cell Biology
|September 24, 1999
Summary
The mdmx gene maintains consistent expression during cell growth and DNA damage, unlike mdm-2. This suggests a constant MdmX protein level, potentially forming a p53:MdmX reservoir in undamaged cells.
Area of Science:
- Molecular Biology
- Cancer Biology
- Cellular Regulation
Background:
- The mdmx gene is homologous to mdm-2 and encodes a protein that binds and inhibits p53 transactivation.
- Mdm-2 protein also inhibits the growth-suppressive activity of the p53 tumor-suppressor protein.
- Understanding mdmx expression patterns is crucial for comprehending p53 regulation.
Purpose of the Study:
- To examine the expression patterns of mdmx in various cell culture systems.
- To determine how MdmX expression correlates with p53 protein levels.
- To investigate the interaction between p53 and MdmX following DNA damage and posttranslational modifications.
Main Methods:
- Analysis of mdmx gene and protein expression in murine fibroblasts, teratocarcinoma cells, and preadipocytes.
- Comparison of mdmx and mdm-2 expression patterns following serum deprivation/restimulation and cisplatin-induced DNA damage.
- In vitro examination of p53:MdmX complexes after DNA-PK phosphorylation.
Main Results:
- mdmx gene expression was constitutive during cell proliferation, differentiation, and serum deprivation/restimulation.
- Unlike mdm-2, mdmx expression did not increase after cisplatin damage to ovarian carcinoma cells.
- DNA-PK phosphorylation of p53 inhibited p53:MdmX association, suggesting posttranslational modifications can block interaction during DNA damage.
Conclusions:
- mdmx gene expression remains constitutive in the examined cell lines, regardless of cell proliferation, differentiation, or DNA damage.
- Cells maintain a constant level of MdmX protein.
- A potential MdmX:p53 reservoir exists in undamaged cells, influencing p53 activity.
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