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Characterization of cells transformed by the human polyomavirus JC virus
Abstract:
One unique feature of the prototype JC virus (JCV) (Mad 1) genome is the occurrence of a second TATA sequence within the early promoter region. A naturally occurring oncogenic variant of JCV (Mad 4) lacks this second TATA box. Several cell lines transformed by Mad 1, Mad 4 and simian virus 40 were characterized, in part to investigate whether the second TATA sequence is functional. S1 nuclease mapping of early JCV gene transcription products revealed a major set of start sites common to both Mad 1 and Mad 4 mRNAs. In addition, a second set of early transcripts was found exclusively in Mad 1 transformants, presumably positioned by the second TATA box. The presence of these unique mRNAs in the Mad 1-transformed cells did not appear to have any bearing on the other parameters investigated, including size and quantity of early viral proteins, integration patterns of viral DNA and growth properties of the cells.
Insights
The JC virus (JCV) Mad 1 genome has a second TATA sequence, unlike the Mad 4 variant. This sequence generates unique early transcripts in Mad 1 cells, but doesn't affect viral protein, DNA integration, or cell growth.
Area of Science:
- Virology
- Molecular Biology
- Genetics
Background:
- The JC virus (JCV) genome, specifically the prototype Mad 1 strain, possesses a distinctive second TATA sequence in its early promoter region.
- An oncogenic variant, JCV Mad 4, naturally lacks this second TATA box, suggesting functional significance.
Purpose of the Study:
- To investigate the functionality of the second TATA sequence in the JCV Mad 1 genome.
- To compare transcriptional products and cellular characteristics of cells transformed by JCV Mad 1, JCV Mad 4, and simian virus 40.
Main Methods:
- S1 nuclease mapping was employed to analyze early JCV gene transcription products.
- Characterization of cell lines transformed by different JCV strains and simian virus 40.
Main Results:
- A primary set of transcription start sites for early mRNAs was identified and found to be common to both JCV Mad 1 and Mad 4.
- A distinct, secondary set of early transcripts was exclusively detected in Mad 1-transformed cells, correlating with the presence of the second TATA box.
- No significant differences were observed in viral protein characteristics, viral DNA integration patterns, or cellular growth properties between Mad 1 and Mad 4 transformed cells.
Conclusions:
- The second TATA sequence in the JCV Mad 1 genome is functional, leading to the production of unique early transcripts.
- Despite generating distinct mRNA populations, the second TATA sequence does not appear to influence key cellular or viral parameters investigated in this study.