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Oncornavirus expression in human x mouse hybrid cells segregating mouse chromosomes
Summary
Human x mouse hybrid cells spontaneously express type C viruses, identified as HMV1. These viruses, isolated from segregating hybrid cells, show characteristics similar to Rauscher murine leukemia virus and can rescue defective murine sarcoma virus.
Area of Science:
- Virology
- Cell Biology
- Genetics
Background:
- Human x mouse hybrid cell lines were generated by fusing human VA2 cells with mouse brain cells.
- These hybrid cells preferentially lose mouse chromosomes while retaining human chromosomes.
Purpose of the Study:
- To investigate the spontaneous expression of type C virus particles in human x mouse hybrid cells.
- To characterize the properties and biological activity of any expressed viruses.
Main Methods:
- Fusion of human and mouse cells to create hybrid clones.
- Culture fluid analysis for type C particle markers and DNA polymerase activity.
- Electron microscopy for particle visualization.
- Sucrose gradient centrifugation and immunological assays for virus characterization.
- Host range studies and rescue assays for defective murine sarcoma virus.
Main Results:
- One hybrid cell line abundantly expressed type C virus particles (HMV1), confirmed by electron microscopy.
- HMV1 banded at 1.14-1.16 g/ml, possessed group-specific antigens, and showed B-tropic replication in mouse cells but not human cells.
- HMV1 rescued defective murine sarcoma virus and exhibited DNA polymerase activity similar to Rauscher murine leukemia virus.
Conclusions:
- Human x mouse hybrid cells losing mouse chromosomes can spontaneously express endogenous type C viruses.
- These hybrid cell lines are valuable tools for isolating latent mammalian oncornaviruses.
- The study provides insights into viral gene regulation and the characterization of novel retroviruses.