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Interactions of polyoma and mouse DNA's. II. Polyoma-induced mouse DNA replication and pseudovirion formation
Abstract:
Secondary mouse embryo (ME) cultures which had been grown prior to infection in the presence of 5-bromodeoxyuridine (BUdR) and 5-fluorodeoxy-uridine were found to be permissive for polyoma virus (16). The DNA extracted from the progeny virus yielded two bands on CsCl isopycnic centrifugation. The light band (LL) contained supercoiled circular (polyoma DNA I), open circular (polyoma DNA II), and linear (polyoma DNA III) molecules, as was seen by electron microscopy. The hybrid band (HL) contained exclusively linear molecules. This DNA was pure, density - labeled, pseudovirion DNA, i.e., fragmented HL mouse DNA. The quantitative comparison of HL and LL polyoma DNA III from six different virus preparations always revealed an excess of HL DNA, the ratio of HL/LL being between 1.2 and 2.2. These results led to the conclusion that in BUdR-prelabeled, polyoma-infected ME cells pseudovirion DNA is excised both from unreplicated and newly replicated regions of mouse DNA.
Insights
Polyoma virus infection in pre-labeled mouse embryo cells produces pseudovirion DNA. This DNA, a hybrid of viral and mouse DNA, is excised from both replicated and unreplicated cellular DNA regions.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- Polyoma virus infects mouse embryo cells.
- Cellular DNA can be labeled with 5-bromodeoxyuridine (BUdR).
Purpose of the Study:
- To investigate the nature of DNA produced by polyoma virus in BUdR-prelabeled mouse embryo cells.
- To determine the origin of pseudovirion DNA.
Main Methods:
- Secondary mouse embryo cultures were grown in the presence of BUdR.
- Cells were infected with polyoma virus.
- DNA was extracted from progeny virus and analyzed using CsCl isopycnic centrifugation and electron microscopy.
Main Results:
- Two DNA bands were observed: a light band (LL) containing viral DNA (supercoiled, open circular, linear) and a hybrid band (HL) containing linear, density-labeled mouse DNA fragments (pseudovirion DNA).
- The HL band, containing pseudovirion DNA, was consistently in excess compared to the LL band.
- Pseudovirion DNA was found to be exclusively linear.
Conclusions:
- Pseudovirion DNA is excised from both unreplicated and newly replicated regions of mouse DNA in BUdR-prelabeled, polyoma-infected cells.
- This indicates a mechanism for incorporating host DNA fragments into viral particles.