Alterations of Protein Synthesis in Arbovirus-Infected L Cells

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Abstract
Cellular protein synthesis and ribonucleic acid (RNA) synthesis in mouse L cells were markedly depressed 1 hr after infection with Venezuelan equine encephalomyelitis virus. Host RNA and protein synthesis were inhibited more rapidly by the virus infection than by actinomycin D. In cells infected 4 hr, a cytoplasmic RNA polymerase was demonstrated which was absent in uninfected cells. At this time, deoxyribonucleic acid-directed RNA synthesis catalyzed by the nuclear RNA polymerase was inhibited in vitro in enzyme preparations from nuclei of virus-infected cells. For optimal activity, the cytoplasmic RNA polymerase required the four nucleoside triphosphates, Mg++, and RNA. The enzyme was insensitive to actinomycin D and deoxyribo-nuclease, indicating that it catalyzed RNA-directed RNA synthesis. Attempts to purify the induced polymerase further were unsuccessful. Fresh preparations had to be used because the enzymatic activity was unstable.