Inhibition of HeLa Cell Protein Synthesis by the Vaccinia Virion

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Abstract
HeLa cell protein synthesis is rapidly suppressed after infection with purified vaccinia virus. This was measured in three ways. (i) In the presence of 5 μg of actinomycin D per ml, viral protein synthesis was prevented and the decline in host protein synthesis was measured directly. (ii) Virus particles irradiated with 800 ergs or more of ultraviolet (UV) light per mm 2 are defective in their ability to initiate viral protein synthesis, but they still inhibit host protein synthesis. After addition of UV-irradiated virus, the decline in host protein synthesis was measured. (iii) Polyacrylamide gel electrophoresis was used to distinguish between host- and virus-induced proteins. The following results were obtained. (i) The inhibition of HeLa cell protein synthesis begins within 20 min after infection with purified vaccinia particles. Greater than 95% inhibition occurs within 1 to 4 hr after infection, depending on the viral multiplicity used. (ii) The synthesis of viral ribonucleic acid or viral protein is not required for the inhibition of host protein synthesis. (iii) The ability of the virus particles to inhibit cell protein synthesis is lost after heat or detergent treatment. (iv) The ability of the virus particles to inhibit cell protein synthesis is retained after UV-irradiation. (v) Vaccinia viral protein synthesis in preinfected cells is resistant to the effects of superinfection with UV-irradiated vaccinia particles. (vi) Inhibition of cell protein synthesis is complete and does not involve the continued synthesis of small polypeptide fragments. (vii) A decrease in the size of host polyribosomes rapidly follows infection with vaccinia virus. The results are interpreted as a selective effect of some constituent of the vaccinia virus particle or virus-activated host enzyme on host protein synthesis at a level beyond that of transcription.