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Interrelation between viral and cellular DNA synthesis in mouse cells infected with the parvovirus minute virus of
Abstract:
Mouse fibroblasts arrested in G0 by isoleucine deprivation were inoculated with the autonomous parvovirus minute virus of mice (MVM). Infected cells were released from the G0 block by transfer to complete medium and their progression to and and through the S phase was monitored. The onset of viral and cellular DNA synthesis coincided, suggesting that cellular factor(s) required for MVM DNA replication became available as soon as cells entered the S phase. Cellular DNA synthesis was reduced to about 60% by MVM infection. However, this inhibition did not decrease significantly the overall rate of DNA replication in infected cells because it was compensated by concomitant viral DNA synthesis. MVM infection delayed the movement of the cells out of S phase by at least 5 h. At any time post-infection, more than 95% of both viral and cellular DNA synthesis was sensitive to inhibition by aphidicolin. Since this drug is highly specific for cellular DNA polymerase alpha, the data are consistent with a major role of this enzyme in the in vivo DNA replication of autonomous parvovirus. The assembly of 95% of virus progeny particles was concomitant with a late phase or viral DNA replication which accounted for 30% of the total viral DNA synthesized. The inhibition of this residual viral DNA replication by aphidicolin reduced dramatically the size of the burst of infectious particles; this observation concurs with other evidence to suggest that encapsidation is driven by a late replication event sensitive to this drug.
Insights
Minute virus of mice (MVM) infection in G0-arrested mouse fibroblasts coincides with cellular DNA synthesis upon cell cycle re-entry. MVM utilizes cellular DNA polymerase alpha for replication, impacting host DNA synthesis and progeny virus production.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- Autonomous parvoviruses, like minute virus of mice (MVM), require host cell machinery for replication.
- Understanding viral DNA replication mechanisms is crucial for developing antiviral strategies.
Purpose of the Study:
- To investigate the interplay between MVM DNA replication and host cell cycle progression.
- To elucidate the role of cellular DNA polymerase alpha in MVM replication.
Main Methods:
- Mouse fibroblasts were arrested in G0 and infected with MVM.
- Cells were released into S phase, and viral and cellular DNA synthesis were monitored.
- The effect of aphidicolin, a DNA polymerase alpha inhibitor, on DNA synthesis and viral progeny production was assessed.
Main Results:
- MVM infection and cellular DNA synthesis onset coincided upon release into S phase.
- MVM infection reduced cellular DNA synthesis but was compensated by viral DNA synthesis.
- Aphidicolin sensitivity indicated a significant role for DNA polymerase alpha in both viral and cellular DNA replication.
- Virus progeny assembly correlated with a late, aphidicolin-sensitive viral DNA replication phase.
Conclusions:
- Cellular factors necessary for MVM replication become available upon entry into S phase.
- Cellular DNA polymerase alpha is essential for MVM DNA replication in vivo.
- Late viral DNA replication, dependent on DNA polymerase alpha, is critical for efficient virus particle assembly.