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Published on: July 13, 2019
Negative regulation of early polyomavirus expression in mouse embryonal carcinoma cells
Abstract:
Embryonal carcinoma cells are resistant to infection by polyomavirus (Py). We showed that this block was partially removed by inhibiting protein synthesis temporarily. The block was also partially removed when Py was coinfected with simian virus 40. Cycloheximide treatment of cells infected with Py mutants able to grow on PCC4 embryonal carcinoma cells led to 3- to 10-fold increases in the production of T-antigen-positive cells. At 31 degrees C, Py T-antigen expression was enhanced when the cells were treated with cycloheximide. We suggest that a negative labile regulatory protein(s) is synthesized in PCC4 cells, preventing the initiation of early Py transcription by binding to the noncoding sequence, especially the enhancer element B and perhaps also element A, and that the Py mutants retained a binding site(s).
Insights
Embryonal carcinoma cells resist polyomavirus (Py) infection. Inhibiting protein synthesis or coinfecting with simian virus 40 partially overcomes this, suggesting a labile protein blocks early Py transcription.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- Embryonal carcinoma (EC) cells exhibit resistance to polyomavirus (Py) infection.
- Understanding the molecular mechanisms underlying this resistance is crucial for viral pathogenesis studies.
Purpose of the Study:
- To investigate the factors contributing to polyomavirus infection resistance in embryonal carcinoma cells.
- To identify strategies for overcoming this cellular defense mechanism.
Main Methods:
- Treatment of infected cells with cycloheximide to inhibit protein synthesis.
- Coinfection experiments with polyomavirus and simian virus 40.
- Analysis of T-antigen expression in Py-infected PCC4 embryonal carcinoma cells under various conditions.
Main Results:
- Temporary inhibition of protein synthesis partially removed the infection block.
- Coinfection with simian virus 40 also partially alleviated the resistance.
- Cycloheximide treatment of cells infected with specific Py mutants resulted in a 3- to 10-fold increase in T-antigen-positive cells.
- Enhanced Py T-antigen expression was observed at 31°C upon cycloheximide treatment.
Conclusions:
- PCC4 embryonal carcinoma cells likely synthesize a labile regulatory protein that inhibits early Py transcription.
- This protein may bind to noncoding sequences, including enhancer elements A and B, thus preventing viral gene expression.
- Py mutants used in this study appear to retain binding sites for this inhibitory protein.
