Viral and Host Deoxyribonucleic Acid Synthesis in Shope Fibroma Virus-infected Cells as Studied by Means of High-Resolution Autoradiography |
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| Authors: | Raoul Scherrer |
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| Affiliation: | Institut de Recherches sur le Cancer, Laboratoire de Microscopie Electronique, 94 Villejuif, France |
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| Abstract: | Incorporation of (3)H-thymidine by BSC-1 cells infected with Shope fibroma virus was studied by means of high-resolution electron microscopic radioautography. One-hour pulses with the radioactive precursor were given at various times after infection, during a one-step growth cycle of the virus. In the cytoplasm of infected cells, reacted grains occurred over foci of viroplasm; these foci are believed to represent the true sites of viral deoxyribonucleic acid (DNA) replication. Shope fibroma virus DNA synthesis began before 3 hr postinfection, reached a maximum at 8 to 9 hr, and then declined rapidly. It was demonstrated that the decline in (3)H-thymidine uptake is correlated with the onset of viral morphogenesis. In comparison with the noninfected culture, the nuclear labeling, which reflects host DNA metabolism, was slightly reduced by 4 hr postinfection. Inhibition became more marked as infection progressed, and host DNA synthesis was almost completely suppressed in late stages of viral development. |
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